OTHER ASSETS AND ACCOUNTS PAYABLE, ACCRUED EXPENSES AND OTHER LIABILITIES - Other Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
OTHER ASSETS AND ACCOUNTS PAYABLE, ACCRUED EXPENSES AND OTHER LIABILITIES
Unsettled Investment Sales	$ 684,163		$ 684,163		$ 86,033
Receivables	58,785		58,785		26,893
Due from Broker	255,871		255,871		65,154
Oil & Gas Assets, net	0		0		215,243
Deferred Tax Assets, net	176,950		176,950		158,574
Interest Receivable	188,476		188,476		156,026
Fixed Assets, net	722,735		722,735		633,025
Foreign Exchange Contracts and Options	234,358		234,358		188,572
Goodwill	83,500		83,500		83,500
Derivative Assets	41,718		41,718		23,139
Prepaid Taxes	78,527		78,527		84,462
Prepaid Expenses	29,303		29,303		14,596
Operating Lease Right of Use Assets	160,139		160,139		121,101
Deferred Financing Costs	18,520		18,520		12,374
Other	275,312		275,312		139,544
Total	3,008,357		3,008,357		2,008,236
Depreciation, depletion, and amortization of oil and natural gas properties	5,700	$ 4,700	18,100	$ 24,700
Accumulated depreciation and amortization of fixed assets	146,600		146,600		$ 132,700
Depreciation and amortization expense of fixed assets	4,600	4,300	14,200	13,000
Operating lease cost	$ 13,900	$ 12,000	$ 39,700	$ 35,700