FAIR VALUE - Consolidated Funds Summary of Valuation Techniques and Quantitative Information (Details) - Consolidated Funds $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 4,739,686	$ 3,808,234
Level III
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	201,985	244,354
Level III | Credit-oriented investments: | Consumer discretionary | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 2,503	$ 7,658
Level III | Credit-oriented investments: | Consumer discretionary | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%	5.00%
Level III | Credit-oriented investments: | Consumer discretionary | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	15.00%	13.00%
Level III | Credit-oriented investments: | Consumer discretionary | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	14.00%	7.00%
Level III | Credit-oriented investments: | Consumer discretionary | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 42,617	$ 64,147
Level III | Credit-oriented investments: | Consumer staples | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 1,594	$ 7,356
Level III | Credit-oriented investments: | Consumer staples | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%	6.00%
Level III | Credit-oriented investments: | Consumer staples | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	13.00%	12.00%
Level III | Credit-oriented investments: | Consumer staples | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%	7.00%
Level III | Credit-oriented investments: | Consumer staples | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 12,657	$ 23,182
Level III | Credit-oriented investments: | Energy | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value		12,758
Level III | Credit-oriented investments: | Industrials | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 14,607	$ 10,574
Level III | Credit-oriented investments: | Industrials | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	6.00%	5.00%
Level III | Credit-oriented investments: | Industrials | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%	7.00%
Level III | Credit-oriented investments: | Industrials | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	7.00%	6.00%
Level III | Credit-oriented investments: | Industrials | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 29,687	$ 30,531
Level III | Credit-oriented investments: | Industrials | Market approach (comparable companies)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 4,217	$ 4,230
Level III | Credit-oriented investments: | Industrials | Market approach (comparable companies) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Earnings multiple	4	5
Level III | Credit-oriented investments: | Industrials | Market approach (comparable companies) | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Earnings multiple	6	7
Level III | Credit-oriented investments: | Industrials | Market approach (comparable companies) | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Earnings multiple	5	6
Level III | Credit-oriented investments: | Information technology | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 4,933	$ 11,681
Level III | Credit-oriented investments: | Information technology | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%	6.00%
Level III | Credit-oriented investments: | Information technology | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	13.00%	13.00%
Level III | Credit-oriented investments: | Information technology | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%	9.00%
Level III | Credit-oriented investments: | Information technology | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 7,187	$ 5,076
Level III | Credit-oriented investments: | Materials | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 1,209	$ 1,206
Level III | Credit-oriented investments: | Materials | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	10.00%	11.00%
Level III | Credit-oriented investments: | Materials | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%	13.00%
Level III | Credit-oriented investments: | Materials | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%	12.00%
Level III | Credit-oriented investments: | Materials | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 13,967	$ 15,586
Level III | Credit-oriented investments: | Real estate | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 3,346
Level III | Credit-oriented investments: | Real estate | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%
Level III | Credit-oriented investments: | Real estate | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	13.00%
Level III | Credit-oriented investments: | Real estate | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	12.00%
Level III | Credit-oriented investments: | Real estate | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 30,843
Level III | Credit-oriented investments: | Real estate | Recent transaction price
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	336
Level III | Credit-oriented investments: | Other | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 13,320	$ 13,754
Level III | Credit-oriented investments: | Other | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	8.00%	8.00%
Level III | Credit-oriented investments: | Other | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	15.00%	16.00%
Level III | Credit-oriented investments: | Other | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	13.00%	12.00%
Level III | Credit-oriented investments: | Other | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 11,675	$ 9,137
Level III | Credit-oriented investments: | Other | Recent transaction price
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value		20,785
Level III | Equity investments: | Discounted cash flow
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 1,343	$ 1,352
Level III | Equity investments: | Discounted cash flow | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	11.00%	11.00%
Level III | Equity investments: | Discounted cash flow | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	30.00%	33.00%
Level III | Equity investments: | Discounted cash flow | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	13.00%	14.00%
Level III | Equity investments: | Recent market information
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 1,986	$ 1,799
Level III | Equity investments: | Market approach (comparable companies)
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Investments, at fair value	$ 3,958	$ 3,542
Level III | Equity investments: | Market approach (comparable companies) | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Earnings multiple	4	4
Level III | Equity investments: | Market approach (comparable companies) | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Earnings multiple	11	11
Level III | Equity investments: | Market approach (comparable companies) | Weighted Average
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Earnings multiple	7	8