Allowance for Loss-Sharing Obligations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Roll forward of loss contingency accrual
Charge-offs, net	$ 113	$ (1,867)
Loss-Sharing Obligation
Roll forward of loss contingency accrual
Outstanding advances under the Fannie Mae DUS program			$ 100
Loss-Sharing Obligation | Fannie Mae
Roll forward of loss contingency accrual
Beginning balance of the period	30,511	32,408
Provisions for loss sharing	1,205	2,254
Provisions reversal for loan repayments	(732)	(575)
Charge-offs, net	113	(1,867)
Ending balance of the period	31,097	$ 32,220
Maximum quantifiable liability	$ 2,290,000		$ 2,240,000