Management Agreements [Abstract] Management Agreements [Abstract] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Townsend Townsend Group [Member] Townsend Group [Member] Segments [Axis] Segments [Axis] Segments [Domain] Segments [Domain] Direct Investments Investment in Asset Management Businesses [Member] Investment in Asset Management Businesses [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Other Income Other Income [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Fee revenue Revenue from Related Parties Management and other fees Operating Expenses Quarterly Financial Information Disclosure [Abstract] Asset management and other fees, related parties Asset Management and Other Fees from Related Parties Asset Management and Other Fees from Related Parties Selling commission and dealer manager fees, related parties Brokerage Commissions Revenue from Related Parties Brokerage Commissions Revenue from Related Parties Commission expense Sales Commissions and Fees Interest expense Interest Expense Transaction costs Transaction Costs Amount of transaction costs recognized during the period. Total general and administrative expenses General and Administrative Expense Income (loss) before equity in earnings (losses) of unconsolidated ventures and income tax benefit (expense) Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Income (loss) before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax benefit (expense) Income Tax Expense (Benefit) Net income (loss) Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net (income) loss attributable to non-controlling interests Net Income (Loss) Attributable to Noncontrolling Interest Net (income) loss attributable to redeemable non-controlling interests Net Income (Loss) Attributable to Redeemable Noncontrolling Interest Net income (loss) attributable to NorthStar Asset Management Group Inc. common stockholders Net Income (Loss) Attributable to Parent Earnings (loss) per share: Earnings Per Share, Basic and Diluted [Abstract] Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Equity Method Investments and Joint Ventures [Abstract] Investments in Unconsolidated Ventures Equity Method Investments and Joint Ventures Disclosure [Text Block] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] NorthStar Securities NorthStar Securities [Member] NorthStar Securities [Member] Selling commission and dealer manager fees (refer to Note 3) Net commission income Related Party Transaction, Net Commission Revenue Related Party Transaction, Net Commission Revenue Reallowed commission expense Commission Expense, Amount Reallowed Commission Expense, Amount Reallowed Debt Disclosure [Abstract] Borrowings Debt Disclosure [Text Block] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] NorthStar Realty NorthStar Realty Finance Corporation [Member] NorthStar Realty Finance Corporation [Member] NorthStar/RXR New York Metro NorthStar RXR New York Metro [Member] NorthStar RXR New York Metro RXR Realty RXR Realty [Member] RXR Realty [Member] NorthStar Corporate Fund NorthStar Corporate Fund [Member] NorthStar Corporate Fund [Member] NorthStar Capital Fund NorthStar Capital Fund [Member] NorthStar Capital Fund [Member] Retail Companies Affiliated Entity [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Class A shares Common Class A [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Commitment to invest in initial public offering Related Party Transaction, Commitment to Invest in Initial Public Offering Related Party Transaction, Commitment to Invest in Initial Public Offering Commitment to purchase common stock period Related Party Transaction, Commitment To Purchase Common Stock Period Related Party Transaction, Commitment To Purchase Common Stock Period Commitment to invest as distribution support Related Party Transaction, Commitment to Invest as Distribution Support Related Party Transaction, Commitment to Invest as Distribution Support Number of new sponsored companies per year Number of New Sponsored Companies, Annual Maximum Number of New Sponsored Companies, Annual Maximum Commitment to purchase common stock (percent) Related Party Transaction, Commitment To Purchase Common Stock, Percentage Related Party Transaction, Commitment To Purchase Common Stock, Percentage Organization and offering costs (percent of proceeds expected to be raised) Organization and Offering Costs Rate, Percent of Expected Proceeds Organization and Offering Costs Rate, Percent of Expected Proceeds Operating Costs (percent of average invested assets) Operating Costs and Expenses Rate, Percent of Average Invested Assets Operating Costs and Expenses Rate, Percent of Average Invested Assets Operating Costs (percent of net income) Operating Costs and Expenses Rate, Percent of Net Income Operating Costs and Expenses Rate, Percent of Net Income Related party allocated costs Related Party Transaction, Expenses from Transactions with Related Party Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] NorthStar Listed Companies Retail Companies Retail Companies [Member] Retail Companies [Member] Broker-Dealer Broker Dealer [Member] Broker Dealer [Member] Corporate/Other Corporate and Other [Member] Managed Companies and Townsend Acquired and Managed Companies [Member] Acquired and Managed Companies [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of segments Number of Reportable Segments Asset management and other fees Interest expense Compensation expense Labor and Related Expense Other general and administrative expenses Other General and Administrative Expense Equity in earnings (losses) of unconsolidated ventures (refer to Note 4) Income (Loss) from Equity Method Investments Operating income Operating Income (Loss) Equity-based compensation expense Allocated Share-based Compensation Expense Depreciation and amortization expense Depreciation, Depletion and Amortization Unrealized loss Unrealized Gain (Loss) on Investments Reimbursement revenue Reimbursement Revenue Balance Sheet: Balance Sheet Related Disclosures [Abstract] Total assets Assets Investments in unconsolidated ventures Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Accounting Policies [Abstract] 2017 Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months 2018 Finite-Lived Intangible Assets, Amortization Expense, Year Two 2019 Finite-Lived Intangible Assets, Amortization Expense, Year Three 2020 Finite-Lived Intangible Assets, Amortization Expense, Year Four 2021 Finite-Lived Intangible Assets, Amortization Expense, Year Five Thereafter Finite-Lived Intangible Assets, Amortization Expense, after Year Five Net Amount Finite-Lived Intangible Assets, Net Accounts payable and accrued expenses: Accounts Payable and Accrued Liabilities [Abstract] Accrued bonus and related taxes Accrued Bonuses and Related Taxes Accrued Bonuses and Related Taxes Incentive fee compensation Incentive Fee Compensation Incentive Fee Compensation Accrued operating expenses Accrued Operating Expenses Accrued Operating Expenses Accrued payroll Accrued Salaries Accrued interest payable Interest Payable Accrued tax withholding Accrued Tax Withholding Accrued Tax Withholding Dividends payable related to equity-based awards Dividends Payable Accrued equity-based compensation awards Accrued Share-based Compensation Expense Accrued Share-based Compensation Expense Accrued participating interests buyout Accrued Participating Interests Buyout Accrued Participating Interests Buyout Share purchase payable Payables to Broker-Dealers and Clearing Organizations Total Accounts Payable and Accrued Liabilities Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Line Items] Business Acquisition [Line Items] Incentive fees Incentive Fee Percentage Incentive Fee Percentage Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Unconsolidated Ventures Unconsolidated Ventures [Member] Unconsolidated Ventures [Member] Schedule of Equity Method Investments [Line Items] Schedule of Equity Method Investments [Line Items] Total assets Equity Method Investment, Summarized Financial Information, Assets Total liabilities Equity Method Investment, Summarized Financial Information, Liabilities Non-controlling interests Equity Method Investment, Summarized Financial Information, Noncontrolling Interest Total equity Equity Method Investment Summarized Financial Information, Equity Segment Reporting Segment Reporting Disclosure [Text Block] Schedule of Finite-Lived Intangible Assets [Table] Schedule of Finite-Lived Intangible Assets [Table] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Customer relationships Customer Relationships [Member] Performance fees Performance Fees [Member] Performance Fees [Member] Trade names Trade Names [Member] Proprietary technology Proprietary Technology [Member] Proprietary Technology [Member] Finite-Lived Intangible Assets [Line Items] Finite-Lived Intangible Assets [Line Items] Gross Amount Finite-Lived Intangible Assets, Gross Estimated Useful Life Finite-Lived Intangible Asset, Useful Life Accumulated Amortization Finite-Lived Intangible Assets, Accumulated Amortization Goodwill Goodwill Gross Amount, Total Intangible Assets, Gross (Including Goodwill) Intangible Assets, Gross (Including Goodwill) Net Amount, Total Intangible Assets, Net (Including Goodwill) Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Healthcare properties Healthcare Properties [Member] Healthcare Properties [Member] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate [Domain] Real Estate [Domain] Senior housing properties Senior Housing Facilities [Member] Senior Housing Facilities [Member] Medical office properties Medical Office Building [Member] Medical Office Building [Member] Hospitals Hospitals [Member] Hospitals [Member] Skilled nursing facilities Skilled Nursing Facilities [Member] Skilled Nursing Facilities [Member] Colony Capital, Inc. Colony Capital, Inc. [Member] Colony Capital, Inc. [Member] Merger Agreement with NorthStar Realty and Colony Capital, Inc. Merger Agreement with NorthStar Realty and Colony Capital, Inc. [Member] Merger Agreement with NorthStar Realty and Colony Capital, Inc. [Member] Common Stock Common Stock [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving credit facility Revolving Credit Facility [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Common stock conversion ratio Business Acquisition, Common Stock, Conversion Ratio Business Acquisition, Common Stock, Conversion Ratio Ownership interest Business Acquisition, Percentage of Voting Interests Acquired Sale of real estate portfolio (percentage) Divestiture of Interest in Joint Venture, Percentage Divested Divestiture of Interest in Joint Venture, Percentage Divested Proceeds from sale of real estate portfolio Proceeds from Divestiture of Interest in Joint Venture Number of real estate properties Number of Real Estate Properties Implied valuation of healthcare properties Real Estate Investments, Implied Valuation Real Estate Investments, Implied Valuation Special cash dividend declared, prior to closing of Mergers Special dividend (in dollars per share) Dividends Payable, Amount Per Share Aggregate principal amount Line of Credit Facility, Maximum Borrowing Capacity Number of extension options Debt Instrument, Term Extension, Number of Options Debt Instrument, Term Extension, Number of Options Extension options duration period Debt Instrument, Term Extension, Period Debt Instrument, Term Extension, Period Statement of Financial Position [Abstract] Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (shares) Common Stock, Shares Authorized Common stock, shares issued (shares) Common Stock, Shares, Issued Common stock, shares outstanding (shares) Common Stock, Shares, Outstanding Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized (shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (shares) Preferred Stock, Shares Issued Preferred stock, shares outstanding (shares) Preferred Stock, Shares Outstanding Performance stock, par value (in dollars per share) Performance Stock, Par or Stated Value Per Share Performance Stock, Par or Stated Value Per Share Performance stock, shares authorized (shares) Performance Stock, Shares Authorized Performance Stock, Shares Authorized Performance stock, shares issued (shares) Performance Stock, Shares, Issued Performance Stock, Shares, Issued Performance stock, shares outstanding (shares) Performance Stock, Shares, Outstanding Performance Stock, Shares, Outstanding Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Stockholders' Equity Note [Abstract] Option Indexed to Issuer's Equity [Table] Option Indexed to Issuer's Equity [Table] Option Indexed to Issuer's Equity [Axis] Option Indexed to Issuer's Equity [Axis] Option Indexed to Issuer's Equity, Type [Domain] Option Indexed to Issuer's Equity, Type [Domain] Call Option Call Option [Member] Option Indexed to Issuer's Equity [Line Items] Option Indexed to Issuer's Equity [Line Items] Notional amount Derivative, Notional Amount Net premium to be paid Redemption Premium Net value of the consideration range Option Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value Management Agreements Management Agreements and Retail Companies [Text Block] Management Agreements and Retail Companies [Text Block] Dividends Payable [Table] Dividends Payable [Table] Dividends Payable [Line Items] Dividends Payable [Line Items] Dividends declared per share of common stock (in dollars per share) Common Stock, Dividends, Per Share, Declared Income Statement [Abstract] Revenues Revenues [Abstract] Asset management and other fees (refer to Note 3) (2) Other income Other Income Total revenues Revenues Expenses Costs and Expenses [Abstract] Commission expense (refer to Note 3) Other expenses Other Cost and Expense, Operating General and administrative expenses General and Administrative Expense [Abstract] Total general and administrative expenses Depreciation and amortization Total expenses Costs and Expenses Unrealized gain (loss) on investments and other Realized gain (loss) on investments and other Realized Investment Gains (Losses) Income (loss) before equity in earnings (losses) of unconsolidated ventures and income tax benefit (expense) Income (loss) before income tax benefit (expense) Net income (loss) Net income (loss) attributable to NorthStar Asset Management Group Inc. common stockholders Earnings (loss) per share: Earnings Per Share [Abstract] Weighted average number of shares: Weighted Average Number of Shares Outstanding Reconciliation [Abstract] Basic (shares) Weighted Average Number of Shares Outstanding, Basic Dilutive (shares) Weighted Average Number of Shares Outstanding, Diluted Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] NorthStar Listed Companies Listed Companies [Member] Listed Companies [Member] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] NSAM bonus plan NSAM Bonus Plan [Member] NSAM Bonus Plan [Member] Expenses covered by NorthStar Realty Related Party Transactions, Maximum Percent of Expenses Covered by Related Party Related Party Transactions, Maximum Percent of Expenses Covered by Related Party Reimbursement cap on the Additional Allocation Expense Reimbursement Rate, Related Party, Percentage, Maximum Expense Reimbursement Rate, Related Party, Percentage, Maximum Long-term bonus or other compensation reimbursement requirement Related Party Transactions, Management Agreement, Maximum Percent of Compensation Reimbursement Required Related Party Transactions, Management Agreement, Maximum Percent of Compensation Reimbursement Required Percent of long-term bonuses paid under NSAM Bonus Plan Related Party Transactions, Management Agreement, Percent of Compensation Reimbursed Related Party Transactions, Management Agreement, Percent of Compensation Reimbursed Other Liabilities Disclosure [Abstract] Other liabilities: Other Liabilities [Abstract] Townsend Funds liability Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Fund Obligations Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Fund Obligations Deferred tax liability, net Deferred Tax Liabilities, Net Deposit payable Deposits Deferred incentive fees Deferred Revenue Other Other Sundry Liabilities Total Other Liabilities Percentage of obligations Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Ownership Percentage of Fund Obligations Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Ownership Percentage of Fund Obligations Related Party Transactions [Abstract] Island Interest Island Hospitality [Member] Island Hospitality [Member] Base management fee (percent of monthly revenue) Property Management Fee, Percent Fee Base management fee Management Fees, Base Revenue Notes receivable from sale of equity method investment Notes Receivable, Related Party Notes Receivable, Related Party Notes receivable interest rate Related Party Transaction, Rate Proceeds from sale of equity method investments Proceeds from Sale of Equity Method Investments Realized loss on equity method investment Equity Method Investment, Realized Gain (Loss) on Disposal Income Tax Disclosure [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] U.S. federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent U.S. state and local income taxes Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Change in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Transaction costs Effective Income Tax Rate Reconciliation, Transaction Costs, Percent Effective Income Tax Rate Reconciliation, Transaction Costs, Percent Equity-based compensation Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Other permanent items Effective Income Tax Rate Reconciliation, Permanent Adjustments, Percent Effective Income Tax Rate Reconciliation, Permanent Adjustments, Percent Effect of foreign operations taxed at various rates Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Percent Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Income tax benefit (expense) Quarterly Financial Information (Unaudited) Quarterly Financial Information [Text Block] Fair Value Disclosures [Abstract] Fair Value Fair Value Disclosures [Text Block] Number of Funds Investments in and Advances to Affiliates, Balance, Contracts Fair Value Cost Method Investments, Fair Value Disclosure Unfunded Commitments Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments Income Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investee Income Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investee Income Distributions Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Distributions Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Distributions Contributions Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Contributions Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Contributions Notice period Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Investment Redemption, Notice Period Carrying amount of liability Commitments to co-invest total capital in Townsend Funds Business Combination, Future Capital Commitment Requirement Business Combination, Future Capital Commitment Requirement Portion of equity in earnings (losses) Fair Value, Option, Changes in Fair Value, Gain (Loss) Commitments and Contingencies Disclosure [Abstract] Schedule of Minimum Future Rental Payments Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] AHI Venture Corporate Joint Venture [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other assets Other Assets [Member] NorthStar Realty and NorthStar Healthcare NorthStar Realty and NorthStar Healthcare [Member] NorthStar Realty and NorthStar Healthcare [Member] AHI Ventures AHI Ventures [Member] AHI Ventures [Member] Mr. Flaherty Mr. Flaherty [Member] Mr. Flaherty [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Property management fees Property Management Fees [Member] Property Management Fees [Member] Value of assets Assets under Management, Carrying Amount Ownership interest Equity Method Investment, Ownership Percentage Related party expense Shares received in connection with distribution (shares) Equity Method Investment, Dividends or Distributions, Shares Equity Method Investment, Dividends or Distributions, Shares Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] NSAM Stock Plan NSAM Stock Plan [Member] NSAM Stock Plan [Member] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Period One Share-based Compensation Award, Tranche One [Member] Period Two Share-based Compensation Award, Tranche Two [Member] Period Three Share-based Compensation Award, Tranche Three [Member] Period Four Share-based Compensation Award, Tranche Four [Member] Share-based Compensation Award, Tranche Four [Member] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Restricted Stock Units (RSUs) Restricted Stock Units (RSUs) [Member] Performance RSUs [Member] Performance RSUs [Member] Performance RSUs [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Certain Employees Non Executive Employees [Member] Represents the nonexecutive employees of the entity. Executive Officer Executive Officer [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of shares granted in period (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Award vesting period Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Percent of RSUs subject to performance based hurdles Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Percent of Performance-based Equity Instruments Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Percent of Performance-based Equity Instruments Percent of RSUs, subject to performance-based hurdles, total shareholder return Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Percent of Performance-based Equity Instruments, Total Shareholder Return Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Percent of Performance-based Equity Instruments, Total Shareholder Return Employment period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Employment Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Employment Period Percent of RSUs subject to performance based hurdles, total shareholder return, Russell 2000 Index Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Percent of Performance-based Equity Instruments, Total Shareholder Return, Russell 2000 Index Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Percent of Performance-based Equity Instruments, Total Shareholder Return, Russell 2000 Index New grants, Weighted Average Grant Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Fair value assumptions, risk free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Award vesting rights Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Performance-based Conditions, Percentage Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Performance-based Conditions, Percentage Healthcare Strategic Partnership Healthcare Strategic Partnership [Member] Healthcare Strategic Partnership [Member] Mr. Flaherty Investor [Member] Number of common shares issued (shares) Stock Issued During Period, Shares, New Issues Noncontrolling Interest [Abstract] Summary of Redeemable Noncontrolling Interest Redeemable Noncontrolling Interest [Table Text Block] Deferred tax asset Deferred Tax Assets, Gross [Abstract] Equity-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Investments in unconsolidated ventures Deferred Tax Assets, Investments Capital loss Deferred Tax Assets, Capital Loss Carryforwards Other Deferred Tax Assets, Other Valuation allowance Deferred Tax Assets, Valuation Allowance Total deferred tax asset Deferred Tax Assets, Net of Valuation Allowance Deferred tax liability Deferred Tax Liabilities, Gross [Abstract] State tax deduction Deferred Tax Liabilities, State Taxes Deferred Tax Liabilities, State Taxes Intangible assets Deferred Tax Liabilities, Intangible Assets Other Deferred Tax Liabilities, Other Total deferred tax liability Deferred Tax Liabilities, Gross Assets Assets [Abstract] Cash Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents Investments in unconsolidated ventures Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investments in Unconsolidated Ventures Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Investments in Unconsolidated Ventures Intangible assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill Goodwill Other assets acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets Total assets Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets Liabilities Liabilities [Abstract] Accounts payable and accrued expenses Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable and Accrued Liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable and Accrued Liabilities Other liabilities acquired Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other Total liabilities Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities Redeemable non-controlling interests Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Redeemable Noncontrolling Interest Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Redeemable Noncontrolling Interest Total equity Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Equity Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Equity Total liabilities and equity Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities and Equity Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities and Equity Expected goodwill deductible for tax purposes Business Acquisition, Goodwill, Expected Tax Deductible Amount Share deal acquisition Closing adjustment related to dividends Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Equity Interests Total revenues Equity Method Investment, Summarized Financial Information, Revenue Total expenses Equity Method Investment, Summarized Financial Information, Expenses Equity Method Investment, Summarized Financial Information, Expenses Net income (loss) Equity Method Investment, Summarized Financial Information, Gross Profit (Loss) Net (income) loss attributable to non-controlling interests Equity Method Investment, Summarized Financial Information, Income (Loss) Attributable to Noncontrolling Interest Equity Method Investment, Summarized Financial Information, Income (Loss) Attributable to Noncontrolling Interest Net income (loss) attributable to unconsolidated ventures’ Equity Method Investment, Summarized Financial Information, Net Income (Loss) Share-based Compensation [Abstract] Compensation Expense Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Other assets: Other Assets [Abstract] Note receivable Notes Receivable, Related Parties Deferred tax asset, net Deferred Tax Assets, Net Prepaid expenses Prepaid Expense Prepaid income taxes Prepaid Taxes Due from related party Due from Other Related Parties Furniture, fixtures and equipment, net Furniture, Fixtures and Equipment, Net Furniture, Fixtures and Equipment, Net Pending deal costs Accounts Receivable, Pending Deal Costs Accounts Receivable, Pending Deal Costs Security deposits Deposit Assets Other Other Assets, Miscellaneous Due from participating broker-dealers Due from Correspondent Brokers Deferred financing costs, net Debt Issuance Costs, Net Total Other Assets Non-controlling Interests Noncontrolling Interest Disclosure [Text Block] Noncontrolling Interest [Table] Noncontrolling Interest [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Non-controlling Interests Noncontrolling Interest [Member] LTIP Units Long Term Incentive Plan Units [Member] Long Term Incentive Plan Units [Member] Noncontrolling Interest [Line Items] Noncontrolling Interest [Line Items] Non-controlling interest related to LTIP Units Noncontrolling Interest in Operating Partnerships LTIP units outstanding (shares) Shares, Outstanding Ownership and non-controlling interest Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Income attributable to Operating Partnership non-controlling interest Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of Variable Interest Entities [Table] Schedule of Variable Interest Entities [Table] AHI Interest American Healthcare Investors, LLC [Member] American Healthcare Investors, LLC [Member] Variable Interest Entity [Line Items] Variable Interest Entity [Line Items] Business Acquisition, Percentage of Voting Interests Committed to Acquire Business Acquisition, Percentage of Voting Interests Committed to Acquire Business Acquisition, Percentage of Voting Interests Committed to Acquire Ownership interest acquired Ownership interest acquired Income Taxes Income Tax Disclosure [Text Block] Pro forma total revenues Business Acquisition, Pro Forma Revenue Pro forma net income (loss) attributable to common stockholders Business Acquisition, Pro Forma Net Income (Loss) Pro forma EPS - basic (in dollars per share) Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Basic Pro forma EPS - diluted (in dollars per share) Business Acquisition, Pro Forma Income (Loss) from Continuing Operations, Net of Tax, Per Share, Diluted Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Term Loan Term Loans [Member] Represents information pertaining to term loans. Line of Credit Line of Credit [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] January 2016 Term Loan Term Loan Effective January 2016 [Member] Term Loan Effective January 2016 [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Term loan Debt Instrument, Face Amount Repayments of outstanding revolving credit agreement Repayments of Lines of Credit Interest rate floor Debt Instrument, Variable Rate, Basis Floor The floor for the variable rate base of the debt instrument. Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Additional annual base management fee Additional Annual Base Management Fee, Minimum Additional Annual Base Management Fee, Minimum NorthStar Income NorthStar Income [Member] Represents information pertaining to NorthStar Income, a related party of the entity. NorthStar Healthcare Northstar Healthcare Income Inc [Member] Represents information pertaining to NorthStar Healthcare Income, Inc. (NorthStar HealthCare). NorthStar Income II Northstar Income II [Member] Northstar Income II [Member] Offering amount Proceeds from Issuance Initial Public Offering Total capital raised Follow-on Public Offering Follow-on Public Offering Total investments Number of feeder funds Public Offering, Number of Feeder Funds Public Offering, Number of Feeder Funds Issuance of performance common stock (refer to Note 9) Stock Issued During Period, Value, New Issues Deferred acquisition fees Related Party Transaction, Deferred Acquisition Fees Related Party Transaction, Deferred Acquisition Fees Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring Basis Fair Value, Measurements, Recurring [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Reported Value Measurement Reported Value Measurement [Member] Estimate of Fair Value Measurement Estimate of Fair Value Measurement [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair value of securities Available-for-sale Securities Fair value of fund Note receivable, fair value Notes Receivable, Fair Value Disclosure Term Loan, at fair value Debt Instrument, Fair Value Disclosure NSAM Plans NSAM Plans [Member] NSAM Plans [Member] Performance Common Stock Performance Shares [Member] Restricted Stock Restricted Stock [Member] Non-executive employees Management [Member] Number of retired shares (shares) Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Expirations Aggregate shares reserved for future awards (shares) Common Stock, Capital Shares Reserved for Future Issuance Salaries and related expenses Salaries, Wages and Officers' Compensation Equity-based compensation expense Total Equity-based compensation expense to be recognized over the remaining vesting period Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options Transaction costs Business Combination, Acquisition Related Costs Rent expense Operating Leases, Rent Expense Number of days of employment to qualify for 401(k) plan Qualifications for 401(k) Retirement Plan, Number of Days of Employment Qualifications for 401(k) Retirement Plan, Number of Days of Employment Employee matching contribution for the first level of earnings Defined Contribution Plan Employer Match Level One Represents the employer's matching contribution of the first level of employee contributions. Employee match level one Defined Contribution Plan Employer Match Employee Contribution Level One Represents the first level of employee contributions (percentage of compensation), which are matched by the employer. Employee matching contribution for the second level of earnings Defined Contribution Plan Employer Match Level Two Represents the employer's matching contribution of the second level of employee contributions. Employer match level two Defined Contribution Plan Employer Match Employee Contribution Level Two Represents the second level of employee contributions (percentage of compensation), which are matched by the employer. Aggregate matching contribution Defined Contribution Plan, Employer Discretionary Contribution Amount Managed Agreements [Abstract] Managed Agreements [Abstract] Asset Management and Other Fees Asset Management and Other Fee Revenues [Member] Asset Management and Other Fee Revenues [Member] Institutional Capital Fee revenue Operating expense Schedule of Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Dividends Dividends Declared [Table Text Block] Restricted Common Stock Incremental shares vested upon performance hurdle being met (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Summary of Investments in Unconsolidated Ventures Investments in and Advances to Affiliates [Table Text Block] Schedule of Townsend Funds Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table Text Block] Schedule of Summarized Financial Information Equity Method Investments [Table Text Block] Schedule of Compensation Expense Schedule of Compensation Expense [Table Text Block] Schedule of Compensation Expense [Table Text Block] Summary of LTIP Units and Unvested Restricted Stock Schedule of Unvested Restricted Stock and Long Term Incentive Plan Units Roll Forward [Table Text Block] Schedule of Unvested Restricted Stock and Long Term Incentive Plan Units Roll Forward [Table Text Block] Basis of Accounting Basis of Accounting, Policy [Policy Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Non-controlling Interests Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy [Policy Text Block] Estimates Use of Estimates, Policy [Policy Text Block] Reclassifications Reclassification, Policy [Policy Text Block] Cash Cash and Cash Equivalents, Policy [Policy Text Block] Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Business Combinations Business Combinations Policy [Policy Text Block] Intangible Assets Goodwill and Intangible Assets, Policy [Policy Text Block] Securities Marketable Securities, Available-for-sale Securities, Policy [Policy Text Block] Deferred Financing Costs Deferred Charges, Policy [Policy Text Block] Revenue Recognition Revenue Recognition, Sales of Services [Policy Text Block] Allowance for Doubtful Accounts Receivables, Trade and Other Accounts Receivable, Allowance for Doubtful Accounts, Policy [Policy Text Block] Equity-Based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Foreign Currency Foreign Currency Transactions and Translations Policy [Policy Text Block] Comprehensive Income (Loss) Comprehensive Income, Policy [Policy Text Block] Earnings Per Share Earnings Per Share, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Fair Value Measurement Fair Value Measurement, Policy [Policy Text Block] Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Temporary Equity [Roll Forward] Beginning balance Redeemable Noncontrolling Interest, Equity, Carrying Amount Contributions Noncontrolling Interest, Increase from Business Combination Distributions Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Net income (loss) Allocation of redeemable non-controlling interests Redeemable Noncontrolling Interest, Equity, Decrease from Allocation Redeemable Noncontrolling Interest, Equity, Decrease from Allocation Currency translation adjustment and other Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Noncontrolling Interest Ending balance Undistributed earnings Undistributed Earnings of Foreign Subsidiaries Effective tax rate Excess tax benefits Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Unrecognized tax benefits Unrecognized Tax Benefits Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Equity in (earnings) losses of unconsolidated ventures Impairment on convertible debt Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net Allowance for uncollectible accounts Provision for Doubtful Accounts Depreciation and amortization Depreciation Amortization of deferred financing costs Amortization of Debt Issuance Costs Amortization of equity-based compensation Share-based Compensation Unrealized (gain) loss on investments and other Unrealized Gain (Loss) on Investments and Other Cash Flow Impact The cash flow impact charged to earnings in the period for the net change in the fair value and the carrying value, or in the comparative fair values, of investments, debts and interest rate swaps, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period. Realized (gain) loss on investments and other Gain (Loss) on Sale of Investments Deferred income tax, net Deferred Income Taxes and Tax Credits Other income Other Noncash Income Distribution from unconsolidated ventures Proceeds from Equity Method Investment, Dividends or Distributions Straight line rental expense Straight Line Rent Change in assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Restricted cash Increase (Decrease) in Restricted Cash Receivables, net Increase (Decrease) in Accounts Receivable Other assets Increase (Decrease) in Other Operating Assets Other liabilities Increase (Decrease) in Other Operating Liabilities Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Commission payable Increase (Decrease) in Commission Payable Increase (Decrease) in Commission Payable Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Acquisition of Townsend, net (refer to Note 1) Payments to Acquire Businesses, Net of Cash Acquired Investment in convertible debt Payments to Acquire Available-for-sale Securities, Debt Investments in unconsolidated ventures Payments to Acquire Interest in Subsidiaries and Affiliates Distribution from unconsolidated ventures Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital Settlement of acquisition of securities (Refer to Note 6) Payments to Acquire Marketable Securities Payment related to the sale of the Island Interest Payments from Sale of Equity Method Investment Payments from Sale of Equity Method Investment Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Contribution from NorthStar Realty Proceeds from Contributions from Affiliates Borrowings from credit facility Proceeds from Lines of Credit Borrowings from term loan Proceeds from Issuance of Secured Debt Repayment of term loan Repayments of Secured Debt Repayment of credit facility Payment of financing costs Payments of Financing Costs Call Spread Premium, net Payments of Call Spread Premium, Net Payments of Call Spread Premium, Net Repurchase of shares related to equity-based awards and tax withholding Payments Related to Tax Withholding for Share-based Compensation Excess tax benefit from equity-based compensation Excess Tax Benefit from Share-based Compensation, Financing Activities Dividends Payments of Ordinary Dividends, Common Stock Contributions from redeemable non-controlling interests Proceeds from Noncontrolling Interests Distributions to redeemable non-controlling interests Payments of Ordinary Dividends, Noncontrolling Interest Retirement of shares of common stock Payments for Repurchase of Common Stock Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations Effect of foreign exchange rate changes on cash Effect of Exchange Rate on Cash Net increase (decrease) in cash Cash and Cash Equivalents, Period Increase (Decrease) Cash - beginning of period Cash and Cash Equivalents, at Carrying Value Cash - end of period Supplemental disclosure of non-cash investing and financing activities: Noncash Investing and Financing Items [Abstract] Contributions from redeemable non-controlling interests Contributions from Redeemable Noncontrolling Interests Contributions from Redeemable Noncontrolling Interests Note receivable from third party related to the sale of the Island Interest Assumption of deferred tax liability Liabilities Assumed Reclassification related to measurement adjustments/other Reclassification Related to Measurement Period Adjustments and Other Reclassification Related to Measurement Period Adjustments and Other Reallocation of non-controlling interests in the NSAM OP Noncash or Part Noncash Transaction, Noncontrolling Interest, Reallocation of Interest in Partnership Noncash or Part Noncash Transaction, Noncontrolling Interest, Reallocation of Interest in Partnership Tax effect related to the vesting of equity-based awards Income Tax Adjustment, Restricted Stock Units, Vested in Period Income Tax Adjustment, Restricted Stock Units, Vested in Period Issuance of common stock related to settlement of award (refer to Note 9) Stock Issued Related to Settlement Stock Issued Related to Settlement Allocation of redeemable non-controlling interests in Townsend Noncash or Part Noncash Transaction, Noncontrolling Interest, Allocation of Redeemable Noncontrolling Interest Noncash or Part Noncash Transaction, Noncontrolling Interest, Allocation of Redeemable Noncontrolling Interest Dividend payable related to RSUs Noncash Dividends Payable, Current and Noncurrent Noncash Dividends Payable, Current and Noncurrent Conversion of LTIP Units to common stock Conversion of Stock, Amount Converted Issuance of common stock related to transactions (refer to Note 4) Stock Issued Related to Transactions Stock Issued Related to Transactions Conversion of Deferred LTIP Units to LTIP Units Conversion of Stock under Incentive and Share-based Compensation Plans Conversion of Stock under Incentive and Share-based Compensation Plans Deemed capital contribution from NorthStar Realty Noncash and Part Noncash Transactions, Deemed Contributions From Noncontrolling Interest Noncash and Part Noncash Transactions, Deemed Contributions From Noncontrolling Interest Accrued transaction costs relating to investments in unconsolidated ventures Investments in Affiliates, Unconsolidated Joint Ventures Investments in Affiliates, Unconsolidated Joint Ventures Distribution from unconsolidated ventures Proceeds from Equity Method Investment, Non-cash Distributions Proceeds from Equity Method Investment, Non-cash Distributions Equity incentive plan Noncash or Part Noncash, Equity Incentive Plan Noncash or Part Noncash, Equity Incentive Plan Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] Payment of interest expense Interest Paid Payment of income tax Income Taxes Paid NorthStar Europe NorthStar Realty Europe Corp. [Member] NorthStar Realty Europe Corp. [Member] Base management fee Base Management Fee [Member] Base Management Fee [Member] Incentive fee Incentive Fees [Member] Incentive Fees [Member] Incentive Fee Range [Axis] Incentive Fee Range [Axis] Incentive Fee Range [Axis] Incentive Fee Range [Domain] Incentive Fee Range [Domain] [Domain] for Incentive Fee Range [Axis] Excess of $0.68 and up to $0.78 Range one [Member] Range one [Member] Excess of $0.78 Range Two [Member] Range Two [Member] Excess of $0.30 and up to $0.36 Range Three [Member] Range Three [Member] Excess of $0.36 Range Four [Member] Range Four [Member] Current in place annual base management fee Related Party Transaction, Annual Base Management Fee Agreement Related Party Transaction, Annual Base Management Fee Agreement Incentive fee hurdle Cumulative cash available for distribution (CAD) per share (in dollars per share) Incentive Fee Per Share Incentive Fee Per Share Base management fee increase per annum Annual Asset Management Fee Rate Represents the annual management fee rate. Schedule of Segment Reporting Information Schedule of Segment Reporting Information, by Segment [Table Text Block] Restricted Stock / LTIP Units / RSUs with Service Conditions Service-Based Awards [Member] Service-Based Awards [Member] Equity-Based Awards with Performance Conditions Performance-Based Awards [Member] Performance-Based Awards [Member] Contingent Consideration by Type [Axis] Contingent Consideration by Type [Axis] Contingent Consideration Type [Domain] Contingent Consideration Type [Domain] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Forecast Scenario, Forecast [Member] Cash paid to acquire business Payments to Acquire Businesses, Gross Cash and stock consideration Business Combination, Consideration Transferred Number of shares acquired (shares) Business Acquisition, Equity Interest Issued or Issuable, Number of Shares Number of principals for continued service Number of Principals for Continued Service Number of Principals for Continued Service Percentage of shares subject to forfeiture conditions Business Acquisition, Percentage of Shares Subject to Forfeiture Conditions Business Acquisition, Percentage of Shares Subject to Forfeiture Conditions Lapsing period for first 50% of shares Forfeiture Conditions, Lapsing Period for First Fifty Percent of Shares Forfeiture Conditions, Lapsing Period for First Fifty Percent of Shares Lapsing period for remaining 50% of shares Forfeiture Conditions, Lapsing Period for Remaining Fifty Percent of Shares Forfeiture Conditions, Lapsing Period for Remaining Fifty Percent of Shares Contribution of equity incentives Adjustments to Additional Paid in Capital, Share-based Compensation, Other Long-term Incentive Plans, Requisite Service Period Recognition Document and Entity Information -- None. No documentation exists for this element. -- Entities [Table] Entities [Table] Class B shares Common Class B [Member] Entity Information [Line Items] Entity Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Entity Current Reporting Status Entity Current Reporting Status Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Amendment Flag Amendment Flag Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Public Float Entity Public Float Authorized repurchase of common stock Stock Repurchase Program, Authorized Amount Common shares repurchased (shares) Common Stock, Shares Repurchased Common Stock, Shares Repurchased Common stock repurchased Proceeds from (Repurchase of) Equity Loan Agreement Loans Payable [Member] NorthStar Listed Shares Borrowing capacity Financial covenant, unrestricted cash or cash equivalents amount Line of Credit Facility, Financial Covenant, Unrestricted Cash or Cash Equivalents Amount Represents the amount of unrestricted cash or cash equivalents required to be maintained at all times under the terms of financial covenant of the debt instrument. Credit facility Long-term Line of Credit Loan Agreement Loan agreement, interest rate Debt Instrument, Interest Rate, Stated Percentage Shares purchased (shares) Related Party Stock Purchased During Period Shares Number of common shares purchased during the period. Value of shares purchased Payments to Acquire Available-for-sale Securities Unrealized loss Unrealized Gain (Loss) on Securities Dividend income Investment Income, Dividend Cash Restricted cash Restricted Cash and Cash Equivalents, Current Receivables, net (refer to Note 3) Due from Related Parties Investments in unconsolidated ventures (refer to Note 4) Securities, at fair value (refer to Note 6) Intangible assets, net Intangible Assets, Net (Excluding Goodwill) Other assets Total assets Term loan, net Secured Debt Accounts payable and accrued expenses Commission payable Accounts Payable, Commission Accounts Payable, Commission Other liabilities Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Redeemable non-controlling interests Equity Liabilities and Equity [Abstract] Performance common stock, $0.01 par value, 500,000,000 shares authorized, 5,210,113 and 4,213,156 shares issued and outstanding as of December 31, 2016 and 2015, respectively Performance Stock, Value, Issued Performance Stock, Value, Issued Preferred stock, $0.01 par value, 100,000,000 shares authorized, no shares issued and outstanding as of December 31, 2016 and 2015 Preferred Stock, Value, Issued Common stock, $0.01 par value, 1,000,000,000 shares authorized, 188,429,725 and 185,685,124 shares issued and outstanding as of December 31, 2016 and 2015, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax Retained earnings (accumulated deficit) Retained Earnings (Accumulated Deficit) Total NorthStar Asset Management Group Inc. stockholders’ equity Stockholders' Equity Attributable to Parent Non-controlling interests Stockholders' Equity Attributable to Noncontrolling Interest Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Total liabilities and equity Liabilities and Equity Schedule of Allocation of Purchase Price Schedule of Business Acquisitions, by Acquisition [Table Text Block] Summary of Pro Forma Amounts Business Acquisition, Pro Forma Information [Table Text Block] Schedule of Intangible Assets Schedule of Intangible Assets and Goodwill [Table Text Block] Schedule of Annual Amortization for Intangible Assets Finite-lived Intangible Assets Amortization Expense [Table Text Block] Schedule of Other Assets & Liabilities Schedule of Other Assets and Other Liabilities [Table Text Block] Schedule of Accounts Payable and Accrued Expenses Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Stockholders' Equity Stockholders' Equity Note Disclosure [Text Block] 2017 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2018 Operating Leases, Future Minimum Payments, Due in Two Years 2019 Operating Leases, Future Minimum Payments, Due in Three Years 2020 Operating Leases, Future Minimum Payments, Due in Four Years 2021 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total minimum lease payments Operating Leases, Future Minimum Payments Due Subsequent Events Subsequent Events [Text Block] North Star Realty Securities North Star Realty Securities LLC [Member] Represents information pertaining to NorthStar Realty Securities , LLC, a wholly-owned broker-dealer subsidiary of the entity. Consideration for acquisition Revenue Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual Net income Business Combination, Pro Forma Information, Earnings or Loss of Acquiree since Acquisition Date, Actual Commission payable Accounts Payable, Commission, Including Related Parties Accounts Payable, Commission, Including Related Parties Commission payable due to employees Accounts Payable, Commission, Payable to Employees Accounts Payable, Commission, Payable to Employees Allowance for doubtful accounts Allowance for Doubtful Accounts Receivable Statement of Comprehensive Income [Abstract] Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Foreign currency translation adjustment, net Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Total other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Redeemable Noncontrolling Interest Other Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Redeemable Noncontrolling Interest Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Comprehensive (income) loss attributable to non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest Comprehensive (income) loss attributable to redeemable non-controlling interests Comprehensive Income (Loss), Net of Tax, Attributable to Redeemable Noncontrolling Interest Comprehensive Income (Loss), Net of Tax, Attributable to Redeemable Noncontrolling Interest Comprehensive income (loss) attributable to NorthStar Asset Management Group Inc. common stockholders Comprehensive Income (Loss), Net of Tax, Attributable to Parent Northstar Realty Equity Plan Northstar Realty Equity Plan [Member] Northstar Realty Equity Plan [Member] NorthStar Realty Bonus Plan NorthStar Realty Bonus Plan [Member] NorthStar Realty Bonus Plan [Member] NSAM Spin-off NSAM Spin-off [Member] NSAM Spin-off [Member] Mr. James F. Flaherty III Mr. James F. Flaherty III [Member] Mr. James F. Flaherty III [Member] Healthcare Strategic Partnership Townsend grants Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Beginning balance (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Grants (shares) Vesting (shares) Conversions (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Conversion in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Conversion in Period Forfeited or canceled grants (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Ending balance (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Beginning Balance, Weighted Average Grant Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Vesting of restricted stock, Weighted Average Grant Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Converted grants, Weighted Average Grant Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Conversions, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Conversions, Weighted Average Grant Date Fair Value Forfeited or canceled grants, Weighted Average Grant Price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Ending Balance, Weighted Average Grant Price (in dollars per share) Restricted stock vested to common stock (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Minimum Statutory Withholding Requirements, Vested in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Minimum Statutory Withholding Requirements, Vested in Period Restricted stock retired to satisfy minimum statutory requirement (shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Minimum Statutory Withholding Requirements, Retired in Period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Minimum Statutory Withholding Requirements, Retired in Period Shares issued (shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Schedule of Components of Income Tax Expense (Benefit) Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Effective Income Tax Rate Reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Related Party Arrangements Related Party Transactions Disclosure [Text Block] Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] U.S. federal Current Federal Tax Expense (Benefit) U.S. state and local Current State and Local Tax Expense (Benefit) Non-U.S. Current Foreign Tax Expense (Benefit) Subtotal current Current Income Tax Expense (Benefit) Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] U.S. federal Deferred Federal Income Tax Expense (Benefit) U.S. state and local Deferred State and Local Income Tax Expense (Benefit) Non-U.S. Deferred Foreign Income Tax Expense (Benefit) Subtotal deferred Deferred Income Tax Expense (Benefit) Income tax benefit (expense) Base Management Fee and Incentive Fee Base Management and Incentive Fee Revenues [Member] Base Management and Incentive Fee Revenues [Member] Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] Schedule of Asset Management and Other Fees with Retail Companies Schedule of Asset Management and Other Fees [Table Text Block] Schedule of Asset Management and Other Fees [Table Text Block] Schedule of Net Commission Revenue Schedule of Net Commission Revenue [Table Text Block] Schedule of Net Commission Revenue [Table Text Block] Trail Commission Distribution Fees, Trail Commission [Member] Distribution Fees, Trail Commission [Member] Class T shares Common Class T [Member] Common Class T [Member] Class D shares Common Class D [Member] Common Class D [Member] Selling commission as percentage of gross primary offering proceeds Selling Commission Rate, Percent of Gross Offering Proceeds Selling Commission Rate, Percent of Gross Offering Proceeds Dealer manager fee rate, percent of gross proceeds Dealer Manager Fee Rate, Percent of Gross Proceeds Dealer Manager Fee Rate, Percent of Gross Proceeds Business and Organization Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Total NorthStar Stockholders’ Equity Parent [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Retained Earnings (Accumulated Deficit) Retained Earnings [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance (shares) Beginning Balance Capital contribution of NorthStar Realty (shares) Stock Issued During Period, Shares, Issued for Services Capital contribution of NorthStar Realty Stock Issued During Period, Value, Issued for Services Amortization of equity-based compensation Stock Issued During Period, Value, Share-based Compensation, Amortization Stock Issued During Period, Value, Share-based Compensation, Amortization Issuance of common stock to directors (shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Issuance of common stock related to transactions (shares) Stock Issued During Period, Shares, Purchase of Assets Issuance of common stock related to transactions (refer to Note 4) Stock Issued During Period, Value, Purchase of Assets Issuance of common stock relating to equity-based compensation, net of forfeitures (shares) Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Issuance of common stock relating to equity-based compensation, net of forfeitures Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Settlement of RSUs to common stock, net (shares) Stock Issued During Period, Shares, New Issues, Settlement of Restricted Stock Units to Common Stock Stock Issued During Period, Shares, New Issues, Settlement of Restricted Stock Units to Common Stock Settlement of RSUs to common stock, net (refer to Note 9) Stock Issued During Period, Value, New Issues, Settlement of Restricted Stock Units to Common Stock Stock Issued During Period, Value, New Issues, Settlement of Restricted Stock Units to Common Stock Settlement of RSUs to performance common stock (shares) (refer to Note 9) Stock Issued During Period, Shares, New Issues, Settlement of Restricted Stock Units to Performance Common Stock Stock Issued During Period, Shares, New Issues, Settlement of Restricted Stock Units to Performance Common Stock Settlement of RSUs to performance common stock (refer to Note 9) Stock Issued During Period, Value, New Issues, Settlement of Restricted Stock Units to Performance Common Stock Stock Issued During Period, Value, New Issues, Settlement of Restricted Stock Units to Performance Common Stock Dividends on common stock and equity-based awards (refer to Note 9) Dividends, Common Stock, Cash Restricted Stock, Shares, Tax Withholding Related to Vesting Restricted Stock, Shares, Tax Withholding Related to Vesting Restricted Stock, Shares, Tax Withholding Related to Vesting Restricted Stock, Value, Tax Withholding Related to Vesting Restricted Stock, Value, Tax Withholding Related to Vesting Restricted Stock, Value, Tax Withholding Related to Vesting Excess tax benefit from equity-based compensation Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Conversion of Deferred LTIP Units to LTIP Units and common stock, net (shares) Stock Issued During Period, Shares, Conversion of Units Conversion of Deferred LTIP Units to LTIP Units and common stock, net Stock Issued During Period, Value, Conversion of Units Retirement of shares of common stock (shares) Treasury Stock, Shares, Retired Retirement of shares of common stock Treasury Stock, Retired, Cost Method, Amount Issuance of restricted stock related to Townsend (shares) Stock Issued During Period, Shares, Acquisitions Issuance of restricted stock related to Townsend (refer to Note 9) Stock Issued During Period, Value, Acquisitions Issuance of performance common stock (shares) Reallocation of non-controlling interests in the NSAM OP (refer to Note 11) Noncontrolling Interest, Decrease from Reallocation Noncontrolling Interest, Decrease from Reallocation Call Spread premium, net Adjustments to Additional Paid in Capital, Call Spread Premium, Net Adjustments to Additional Paid in Capital, Call Spread Premium, Net Allocation of redeemable non-controlling interests (refer to Note 11) Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Net income (loss) Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest Ending Balance (shares) Ending Balance Investments in and Advances to Affiliates [Table] Investments in and Advances to Affiliates [Table] AHI Interest, Island Interest, and Townsend Funds American Healthcare Investors, LLC, Island Hospitality, and Townsend Group [Member] American Healthcare Investors, LLC, Island Hospitality, and Townsend Group [Member] Subtotal Indirect Investments American Healthcare Investors LLC and Island Hospitality [Member] American Healthcare Investors LLC and Island Hospitality [Member] Distributed Finance Distributed Finance Corporation [Member] Distributed Finance Corporation [Member] Investments in and Advances to Affiliates [Line Items] Investments in and Advances to Affiliates [Line Items] Indirect Investments Equity Method Investment, Financial Statement, Reported Amounts [Abstract] Ownership Interest Indirect Investments Equity Method Investments Investment Total Investment in the form of convertible debt Payments for Advance to Affiliate Consideration Cash consideration Common stock consideration Business Acquisition, Equity Interest Issued or Issuable, Value Assigned Common stock consideration that vested immediately Business Acquisition, Equity Interest Issued or Issuable, Value Assigned, Vested Business Acquisition, Equity Interest Issued or Issuable, Value Assigned, Vested Distributions Notes Receivable, Fair Value Disclosure Consideration for acquisition Consideration Transferred to Acquire Equity Method Investments Consideration Transferred to Acquire Equity Method Investments Payments to acquire marketplace finance platform Payments to Acquire Equity Method Investments Stock issued Stock Issued Numerator: Net Income (Loss) Attributable to Parent [Abstract] Less: Earnings (loss) allocated to unvested participating securities Participating Securities, Distributed and Undistributed Earnings (Loss), Basic Numerator for basic income (loss) per share Net Income (Loss) Available to Common Stockholders, Basic Add: Undistributed earnings allocated to participating nonvested shares Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted Less: Undistributed earnings reallocated to participating nonvested shares Undistributed Earnings (Loss) Reallocated to Participating Securities, Diluted Undistributed Earnings (Loss) Reallocated to Participating Securities, Diluted Net income (loss) attributable to LTIP Units non-controlling interests Numerator for diluted income (loss) per share Net Income (Loss) Available to Common Stockholders, Diluted Denominator: Weighted Average Number of Shares Outstanding, Basic [Abstract] Weighted average number of shares of common stock (shares) Incremental diluted shares (shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Weighted average number of diluted shares (shares) Diluted (in dollars per share) Special servicing fees Service Fee, Related Party Service Fee, Related Party Payments for administrative services, intercompany transaction Payments for Services, Intercompany Transactions Payments for Services, Intercompany Transactions Advance payments for administrative services, intercompany transaction Payments for Services, Intercompany Transactions, Advance Payment Payments for Services, Intercompany Transactions, Advance Payment Schedule of Quarterly Financial Information Quarterly Financial Information [Table Text Block]