Loan Sales and Servicing Activities - Summary of Cash Flows with Transferees (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows:
Sales proceeds	$ 44,557,560	$ 50,235,245	$ 49,633,909
Servicing fees received	488,483	376,160	261,163
Net servicing advances (recoveries)	28,557	52,353	$ 8,274
Period end information:
Unpaid principal balance of mortgage loans outstanding	145,224,596	120,853,138
30-89 days	6,222,864	5,097,688
90 days or more - Not in foreclosure	2,208,083	2,303,114
90 days or more - In foreclosure	720,894	606,744
90 days or more - Foreclosed	24,243	30,310
Bankruptcy	$ 970,329	$ 657,368