Loan Sales and Servicing Activities - Summary of Cash Flows with Transferees (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
Cash flows:
Sales proceeds	$ 26,683,234	$ 17,897,693	$ 67,209,239	$ 39,084,441
Servicing fees received	166,316	149,210	491,743	426,774
Net servicing advances	71,890	$ 8,605	68,992	$ (23,583)
Period end information:
Unpaid principal balance of loans outstanding	188,854,796		188,854,796		$ 168,842,011
30-89 days	7,237,198		7,237,198		7,947,560
90 days or more - Not in foreclosure	19,423,346		19,423,346		3,237,563
90 days or more - In foreclosure	621,649		621,649		888,136
90 days or more - Foreclosed	13,730		13,730		15,387
Bankruptcy	$ 1,288,443		$ 1,288,443		$ 1,343,816