Loan Sales and Servicing Activities - Summary of Cash Flows with Transferees (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Cash flows:
Sales proceeds	$ 8,536,430	$ 11,103,785
Servicing fees received	137,148	113,091
Net servicing advances (recoveries)	(24,176)	$ (10,637)
Period end information:
Unpaid principal balance of mortgage loans outstanding	148,795,055		$ 145,224,596
30-89 days	5,489,000		6,222,864
90 days or more - Not in foreclosure	2,085,034		2,208,083
90 days or more - In foreclosure	710,297		720,894
90 days or more - Foreclosed	24,875		24,243
Bankruptcy	$ 1,053,399		$ 970,329