Liability for Losses Under Representations and Warranties (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
During the year:
Balance at beginning of quarter	$ 20,587	$ 19,568	$ 20,053	$ 19,067
Provision for losses relating to representations and warranties on loans sold pursuant to mortgage loan sales	1,842	1,596	4,550	4,294
Provision for losses relating to representations and warranties on loans sold reduction in liability due to change in estimate	(1,155)	(1,194)	(3,627)	(3,086)
Incurred losses	(252)	(297)	46	(602)
Balance at end of quarter	21,022	19,673	21,022	19,673
Unpaid principal balance of mortgage loans subject to representations and warranties at period end	$ 139,315,779	$ 114,531,205	$ 139,315,779	$ 114,531,205