Commitments and Contingencies - Summary of Activity in Representations and Warranties Liability (Details) - Commitment to Purchase Loans [Member] - Originations [Member] - Representations And Warranties [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss Contingency Accrual [Roll Forward]
Balance at beginning of the year	$ 23,145	$ 10,959	$ 9,134
Provision for new sales	15,331	16,008	7,741
Change in estimate of existing reserves	(15,660)	(2,419)	(5,068)
Net realized losses on repurchases	722	1,403	848
Balance at end of the year	$ 22,094	$ 23,145	$ 10,959