Loan Sales and Servicing Activities - Summary of Cash Flows with Transferees (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Cash flows:
Sales proceeds	$ 11,375,408	$ 13,600,232	$ 34,208,217	$ 38,097,411
Servicing fees received	123,626	97,312	354,535	272,303
Net servicing advances	4,147	$ (15,061)	(20,572)	$ (1,271)
Period end information:
Unpaid principal balance of mortgage loans outstanding	139,305,079		139,305,079		$ 120,853,138
30-89 days	5,967,607		5,967,607		5,097,688
90 days or more - Not in foreclosure	1,904,299		1,904,299		2,303,114
90 days or more - In foreclosure	640,555		640,555		606,744
90 days or more - Foreclosed	24,216		24,216		30,310
Bankruptcy	$ 889,814		$ 889,814		$ 657,368