Mortgage Servicing Rights - Sensitivity Analysis (Details) - MSR - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Sensitivity analysis
Constant prepayment rate: Impact of 10% adverse change	$ (1,747)		$ (1,747)		$ (2,297)
Constant prepayment rate: Impact of 20% adverse change	(3,441)		(3,441)		(4,471)
Discount rate: Impact of 10% adverse change	(1,889)		(1,889)		(2,539)
Discount rate: Impact of 20% adverse change	(3,630)		(3,630)		$ (4,882)
Contractually specified servicing fees, late fees and ancillary fees	$ 4,200	$ 5,700	$ 15,700	$ 17,300