FAIR VALUE - Consolidated Funds Summary of Changes in Fair Value of Level III Investments (Details) - Consolidated Funds - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Cumulative-effect adjustment from adoption of accounting guidance					$ (27,012,584)
Fair Value, Net Asset (Liability) Measured On Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 224,658	$ 206,990	$ 244,354	$ 27,217,707
Transfers into Level III	4,322	0	24,166	37,933
Transfers out of Level III	(7,651)	(1,962)	(49,120)	(42,670)
Purchases	19,364	2,397	50,571	9,537
Sales	(39,903)	(11,411)	(70,569)	(13,693)
Realized gains (losses), net	223	89	609	115
Unrealized appreciation (depreciation), net	972	(330)	1,974	(572)
Ending balance	201,985	195,773	201,985	195,773
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period	1,664	(2,051)	2,254	(572)
Corporate debt – bank debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	179,080	200,811	208,868	1,871,375
Cumulative-effect adjustment from adoption of accounting guidance					(1,672,305)
Transfers into Level III	2,344	0	22,188	37,535
Transfers out of Level III	(7,651)	(1,962)	(49,120)	(42,670)
Purchases	8,309	2,239	23,317	9,378
Sales	(31,071)	(10,886)	(55,205)	(12,872)
Realized gains (losses), net	107	89	211	115
Unrealized appreciation (depreciation), net	111	(382)	970	(647)
Ending balance	151,229	189,909	151,229	189,909
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period	700	(2,103)	1,147	(647)
Corporate debt – all other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	38,933	1,853	28,793	3,009,164
Cumulative-effect adjustment from adoption of accounting guidance					(3,007,287)
Transfers into Level III	1,978	0	1,978	0
Transfers out of Level III	0	0	0	0
Purchases	10,919	1	27,118	2
Sales	(8,309)	0	(14,725)	0
Realized gains (losses), net	116	0	311	0
Unrealized appreciation (depreciation), net	(168)	36	(6)	11
Ending balance	43,469	1,890	43,469	1,890
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period	(65)	36	97	11
Equities – common stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	6,645	4,326	6,693	8,729,202
Cumulative-effect adjustment from adoption of accounting guidance					(8,725,026)
Transfers into Level III	0	0	0	398
Transfers out of Level III	0	0	0	0
Purchases	136	157	136	157
Sales	(523)	(525)	(639)	(821)
Realized gains (losses), net		0	87	0
Unrealized appreciation (depreciation), net	1,029	16	1,010	64
Ending balance	7,287	3,974	7,287	3,974
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period	1,029	16	1,010	64
Equities – preferred stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			0	1,363,542
Cumulative-effect adjustment from adoption of accounting guidance					(1,363,542)
Transfers into Level III			0	0
Transfers out of Level III			0	0
Purchases			0	0
Sales			0	0
Realized gains (losses), net			0	0
Unrealized appreciation (depreciation), net			0	0
Ending balance	0	0	0	0
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period			0	0
Real estate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			0	9,655,270
Cumulative-effect adjustment from adoption of accounting guidance					(9,655,270)
Transfers into Level III			0	0
Transfers out of Level III			0	0
Purchases			0	0
Sales			0	0
Realized gains (losses), net			0	0
Unrealized appreciation (depreciation), net			0	0
Ending balance	0	0	0	0
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period			0	0
Real estate loan portfolios
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance			0	2,597,405
Cumulative-effect adjustment from adoption of accounting guidance					(2,597,405)
Transfers into Level III			0	0
Transfers out of Level III			0	0
Purchases			0	0
Sales			0	0
Realized gains (losses), net			0	0
Unrealized appreciation (depreciation), net			0	0
Ending balance	0	0	0	0
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period			0	0
Swaps
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Cumulative-effect adjustment from adoption of accounting guidance					$ 8,251
Swaps
Beginning balance			0	(8,251)
Transfers into Level III			0	0
Transfers out of Level III			0	0
Purchases			0	0
Sales			0	0
Realized gains (losses), net			0	0
Unrealized appreciation (depreciation), net			0	0
Ending balance	$ 0	$ 0	0	0
Net change in unrealized appreciation (depreciation) attributable to assets still held at end of period			$ 0	$ 0