OTHER INCOME, GENERAL AND ADMINISTRATIVE, OTHER ASSETS AND LIABILITIES - Schedule of General and Administrative Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Schedule Of Other Income [Line Items]
Legal and professional expense	$ 16,442	$ 11,749	$ 46,352	$ 35,378
Loan origination expense	17,882	7,801	42,349	7,801
Occupancy expense	5,114	4,394	14,079	4,394
Other	19,311	19,323	48,383	36,276
General and Administrative Expense	133,513	98,587	351,359	139,169
Servicing
Schedule Of Other Income [Line Items]
Compensation and benefits expense	30,494	22,498	87,219	22,498
Origination
Schedule Of Other Income [Line Items]
Compensation and benefits expense	$ 44,270	$ 32,822	$ 112,977	$ 32,822