Employee Benefit Plans - Defined Benefit Plans - Components of Periodic Pension Costs (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other components of net periodic benefit cost:
Net periodic benefit cost		$ 403	$ 627	$ 656
Other changes in plan assets and benefit obligations recognized in other comprehensive (income) loss
Amortization of prior service cost arising during the period	[1]	62	61	60
The Bank | Cash Balance Plan
Components of net periodic benefit cost
Service cost, included in salaries and employee benefits		1,232	1,120	1,076
Other components of net periodic benefit cost:
Interest cost		521	552	528
Expected return on plan assets		(1,413)	(1,138)	(1,045)
Amortization of prior service credit		(62)	(61)	(60)
Recognized net actuarial losses		125	154	157
Other components of net periodic benefit cost, included in other noninterest income		(829)	(493)	(420)
Net periodic benefit cost		$ 403	$ 627	$ 656

[1] These items are included in the computation of net periodic benefit cost and are included in “Noninterest income-Other” on the Consolidated Statements of Income. See “Note 12: Employee Benefit Plans,” for additional information.