Loan Sales and Servicing Activities - Summary of Cash Flows with Transferees (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Cash flows:
Sales proceeds	$ 19,337,017	$ 8,536,430
Servicing fees received	166,556	137,148
Net servicing advances	15,209	$ 24,176
Period end information:
Unpaid principal balance of loans outstanding	175,709,882		$ 168,842,011
30-89 days	8,314,858		7,947,560
90 days or more - Not in foreclosure	2,837,903		3,237,563
90 days or more - In foreclosure	832,922		888,136
90 days or more - Foreclosed	18,541		15,387
Bankruptcy	$ 1,364,331		$ 1,343,816