Fair Value of Assets and Liabilities - Reconciliation of Assets with Unobservable Inputs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 10,150	$ 7,165	$ 8,178	$ 5,294
Change included in earnings	(688)	(751)	(1,834)	(935)
Purchases and issuances	5,731	5,092	16,787	14,030
Sales and settlements	(4,381)	(3,817)	(12,319)	(10,700)
Ending balance	10,812	7,689	10,812	7,689
Net change in unrealized gains (losses) relating to items held at end of period	1,117	1,508	1,117	1,508
Mortgage servicing rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	8,733	5,828	7,305	4,157
Change included in earnings	(128)	(296)	(272)	(62)
Purchases and issuances	1,090	649	2,662	2,086
Sales and settlements	0	0	0	0
Ending balance	9,695	6,181	9,695	6,181
Net change in unrealized gains (losses) relating to items held at end of period	0	0	0	0
Interest rate lock commitments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1,417	1,337	873	1,137
Change included in earnings	(560)	(455)	(1,562)	(873)
Purchases and issuances	4,641	4,443	14,125	11,944
Sales and settlements	(4,381)	(3,817)	(12,319)	(10,700)
Ending balance	1,117	1,508	1,117	1,508
Net change in unrealized gains (losses) relating to items held at end of period	$ 1,117	$ 1,508	$ 1,117	$ 1,508