OTHER ASSETS AND LIABILITIES, GENERAL AND ADMINISTRATIVE, AND OTHER ITEMS - Schedule of General and Administrative Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Schedule Of Other Income [Line Items]
Legal and professional expense	$ 18,219	$ 26,037
Loan origination expense	40,245	16,929
Occupancy expense	10,350	8,064
Subservicing expense	49,839	66,981
Loan servicing expense	4,679	7,853
Property and maintenance expense	12,130	7,463
Other miscellaneous general and administrative	28,399	29,153
Total general and administrative expenses	362,505	275,099
Servicing
Schedule Of Other Income [Line Items]
Compensation and benefits expense	65,426	51,341
Origination
Schedule Of Other Income [Line Items]
Compensation and benefits expense	$ 133,218	$ 61,278