DEBT OBLIGATIONS AND CREDIT FACILITIES - Collateralized Loan Obligation Loans Payable (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Carrying Value	$ 800,000	$ 850,000
Less: Debt issuance costs	(4,042)	(3,646)
Debt obligations	795,958	846,354
Consolidated Funds
Debt Instrument [Line Items]
Debt obligations	2,678,566	2,330,359
Assets backing the obligation	3,100,000	2,600,000
Collateralized Loan Obligations \| Consolidated Funds
Debt Instrument [Line Items]
Carrying Value	2,678,566	2,355,060
Less: Debt issuance costs	0	(24,701)
Debt obligations	2,678,566	2,330,359
Collateralized Loan Obligations \| Consolidated Funds \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		2,294,938
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 1
Debt Instrument [Line Items]
Carrying Value	$ 455,509	$ 457,196
Weighted average interest rate (as a percent)	2.63%	2.37%
Weighted Average Remaining Maturity (in years)	8 years 9 months 6 days	9 years 3 months 18 days
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 1 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 447,460
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 1 \| Estimate of Fair Value Measurement \| LIBOR
Debt Instrument [Line Items]
LIBOR margin (as a percent)	2.01%
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 2
Debt Instrument [Line Items]
Carrying Value	$ 456,770	$ 454,423
Weighted average interest rate (as a percent)	2.81%	2.52%
Weighted Average Remaining Maturity (in years)	10 years 6 months	11 years
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 2 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 446,558
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 2 \| Estimate of Fair Value Measurement \| LIBOR
Debt Instrument [Line Items]
LIBOR margin (as a percent)	2.17%
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 3
Debt Instrument [Line Items]
Carrying Value	$ 73,833	$ 79,914
Weighted average interest rate (as a percent)	2.97%	2.96%
Weighted Average Remaining Maturity (in years)	2 years 6 months	3 years
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 3 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 78,632
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 3 \| Estimate of Fair Value Measurement \| Minimum
Debt Instrument [Line Items]
Unused commitment fee (as a percent)	0.00%
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 3 \| Estimate of Fair Value Measurement \| Maximum
Debt Instrument [Line Items]
Unused commitment fee (as a percent)	2.00%
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 4
Debt Instrument [Line Items]
Carrying Value	$ 372,735	$ 363,709
Weighted average interest rate (as a percent)	2.26%	2.26%
Weighted Average Remaining Maturity (in years)	11 years 2 months 12 days	11 years 8 months 12 days
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 4 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 357,626
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 4 \| Estimate of Fair Value Measurement \| EURIBOR
Debt Instrument [Line Items]
Base rate (as a percent)	0.00%
LIBOR margin (as a percent)	2.26%
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 5
Debt Instrument [Line Items]
Carrying Value	$ 457,846	$ 455,295
Weighted average interest rate (as a percent)	2.72%	2.54%
Weighted Average Remaining Maturity (in years)	11 years 6 months	12 years
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 5 \| LIBOR
Debt Instrument [Line Items]
LIBOR margin (as a percent)	2.09%
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 5 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 448,933
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 6
Debt Instrument [Line Items]
Carrying Value	$ 373,649	$ 361,142
Weighted average interest rate (as a percent)	2.29%	2.29%
Weighted Average Remaining Maturity (in years)	11 years 9 months 18 days	12 years 3 months 18 days
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 6 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 359,914
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 6 \| Estimate of Fair Value Measurement \| EURIBOR
Debt Instrument [Line Items]
Base rate (as a percent)	0.00%
LIBOR margin (as a percent)	2.29%
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 7
Debt Instrument [Line Items]
Carrying Value	$ 404,499
Weighted average interest rate (as a percent)	2.28%
Weighted Average Remaining Maturity (in years)	12 years 10 months 24 days
Collateralized Loan Obligations \| Consolidated Funds \| Senior variable rate notes 7 \| Estimate of Fair Value Measurement \| EURIBOR
Debt Instrument [Line Items]
Base rate (as a percent)	0.00%
LIBOR margin (as a percent)	2.28%
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 1
Debt Instrument [Line Items]
Carrying Value	$ 10,758	$ 25,500
Weighted Average Remaining Maturity (in years)	10 years 6 months	11 years
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 1 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 16,400
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 2
Debt Instrument [Line Items]
Carrying Value	$ 17,896	$ 21,183
Weighted Average Remaining Maturity (in years)	11 years 2 months 12 days	11 years 8 months 21 days
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 2 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 15,876
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 3
Debt Instrument [Line Items]
Carrying Value	$ 18,125	$ 25,500
Weighted Average Remaining Maturity (in years)	11 years 6 months	12 years
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 3 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 18,337
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 4
Debt Instrument [Line Items]
Carrying Value	$ 14,766	$ 17,924
Weighted Average Remaining Maturity (in years)	11 years 9 months 18 days	12 years 3 months 18 days
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 4 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 11,928
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 5
Debt Instrument [Line Items]
Carrying Value	$ 22,180	$ 12,036
Weighted Average Remaining Maturity (in years)	12 years 10 months 24 days	1 year 7 months 6 days
Collateralized Loan Obligations \| Consolidated Funds \| Subordinated note 5 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 12,036
Collateralized Loan Obligations \| Consolidated Funds \| Term Loan 2
Debt Instrument [Line Items]
Carrying Value		$ 81,238
Weighted average interest rate (as a percent)		1.20%
Weighted Average Remaining Maturity (in years)		1 year 7 months 6 days
Collateralized Loan Obligations \| Consolidated Funds \| Term Loan 2 \| Estimate of Fair Value Measurement
Debt Instrument [Line Items]
Collateralized loan obligation loans payable		$ 81,238

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Debt Instrument, Weighted Average Remaining Term

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Weighted average interest rate of debt outstanding.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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- Definition

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

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