FAIR VALUE OPTION - Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets	$ 20,154,224	$ 22,032,021
Liabilities	12,608,642	15,586,216
Private Equity
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets	2,975	3,744
Credit
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets	4,681,500	4,381,519
Investments of Consolidated CFEs
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets	13,368,099	15,573,203
Real Assets
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets	344,965	343,820
Equity Method - Other
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets	1,568,220	1,384,739
Other Investments
Fair Value, Option, Quantitative Disclosures [Line Items]
Assets	188,465	344,996
Debt Obligations of Consolidated CFEs
Fair Value, Option, Quantitative Disclosures [Line Items]
Liabilities	$ 12,608,642	$ 15,586,216