SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fees and Commissions [Line Items]
Fees and Other	$ 2,006,791	$ 1,790,475	$ 1,841,326
Carried Interest	1,719,527	2,041,847	441,529
General Partner Capital Interest	504,573	388,578	112,981
Total Capital Allocation-Based Income (Loss)	2,224,100	2,430,425	554,510
Total Revenues	$ 4,230,891	4,220,900	2,395,836
Minimum
Fees and Commissions [Line Items]
Fee Credits as a percentage of monitoring and transaction fees net of fund-related expenses	80.00%
Maximum
Fees and Commissions [Line Items]
Fee Credits as a percentage of monitoring and transaction fees net of fund-related expenses	100.00%
Management Fees
Fees and Commissions [Line Items]
Fees and Other	$ 965,664	824,903	724,558
Fee Credits
Fees and Commissions [Line Items]
Fees and Other	(299,415)	(340,900)	(231,943)
Transaction Fees
Fees and Commissions [Line Items]
Fees and Other	950,205	914,329	988,954
Monitoring Fees
Fees and Commissions [Line Items]
Fees and Other	127,907	106,289	87,545
Incentive Fees
Fees and Commissions [Line Items]
Fees and Other	10,404	0	14,038
Expense Reimbursements
Fees and Commissions [Line Items]
Fees and Other	149,522	169,415	146,989
Oil and Gas Revenue
Fees and Commissions [Line Items]
Fees and Other	21,054	47,153	51,465
Consulting Fees
Fees and Commissions [Line Items]
Fees and Other	$ 81,450	$ 69,286	$ 59,720