Residential Loans at Fair Value - Reconciliation of Changes in Residential Loans Held for Sale to Amounts Presented on Consolidated Statements of Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans Receivable Held-for-sale, Net, Reconciliation to Cash Flow [Roll Forward]
Balance at beginning of the year	$ 1,334,300	$ 1,124,615	$ 1,015,607
Purchases and originations of loans held for sale	21,054,053	25,942,841	18,878,305
Proceeds from sales of and payments on loans held for sale (1)	(21,467,419)	(25,963,200)	(19,177,179)
Realized gains on sales of loans	233,447	171,128	367,314
Change in unrealized gains on loans held for sale	(14,803)	(7,345)	1,412
Interest income	41,824	52,227	40,051
Transfers from loans held for investment	0	16,690	0
Other	(5,122)	(2,656)	(895)
Balance at end of the year	$ 1,176,280	$ 1,334,300	$ 1,124,615