Mortgage Servicing Rights - Mortgage Servicing Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance, beginning of period			$ 7,305
Additions for new MSR capitalized			2,662	$ 2,086
Changes in fair value:
Balance, end of period	$ 9,695		9,695
Balance of mortgage loans serviced for others	$ 516,008		$ 516,008		$ 406,291
MSR as a percentage of serviced loans	1.88%		1.88%		1.80%
Mortgage servicing rights
Servicing Asset at Fair Value, Amount [Roll Forward]
Balance, beginning of period	$ 8,733	$ 5,828	$ 7,305	4,157
Additions for new MSR capitalized	1,090	649	2,662	2,086
Changes in fair value:
Due to changes in model inputs of assumptions	125	(188)	490	332
Other	(253)	(108)	(762)	(394)
Balance, end of period	$ 9,695	$ 6,181	$ 9,695	$ 6,181