Goodwill and Other Intangible Assets - Current Year Amortization Expense for Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Total intangible amortization	$ 1,765	$ 1,766	$ 5,010	$ 4,822
Core Deposit Intangibles
Finite-Lived Intangible Assets [Line Items]
Total intangible amortization	1,732	1,733	4,911	4,723
Customer Relationship Intangible
Finite-Lived Intangible Assets [Line Items]
Total intangible amortization	$ 33	$ 33	$ 99	$ 99