Securitizations and Variable Interests Entities - Summary of Cash Flows Received from and Paid to Securitization Trusts Related to Transfers Accounted for as Sales Outstanding (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Transfers and Servicing [Abstract]
Proceeds received from securitizations	$ 1,248,837	$ 1,290,682	$ 3,256,625
Servicing fees collected (1)	50,326	45,046	41,509
Purchases of previously transferred assets, net of claims reimbursed	(4,602)	(4,395)	(5,948)
Cash flows between transferor and transferee proceeds and payment related to transfers accounted for sales	$ 1,294,561	$ 1,331,333	$ 3,292,186