Goodwill and Other Intangible Assets - Current Year Amortization Expense for Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Total intangible amortization	$ 1,594	$ 1,493	$ 3,245	$ 3,056
Core Deposit Intangibles
Finite-Lived Intangible Assets [Line Items]
Total intangible amortization	1,561	1,460	3,179	2,990
Customer Relationship Intangible
Finite-Lived Intangible Assets [Line Items]
Total intangible amortization	$ 33	$ 33	$ 66	$ 66