Employee Benefit Plans - Pension Plan Assumptions & Contributions (Details) - Pension Plan - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net periodic benefit plan (income) cost included in other non-interest expense
Interest cost	$ 983,000	$ 1,138,000	$ 1,281,000
Return on plan assets	607,000	(1,174,000)	(1,898,000)
Recognized actuarial (gain) loss	(630,000)	765,000	(625,000)
Net periodic benefit plan (income) cost	$ 960,000	$ 729,000	$ (1,242,000)
Assumptions used to determine benefit obligation
Actual return (loss) on plan assets, net of administrative expenses	(1.60%)	3.20%	4.90%
Discount rate	3.30%	3.60%	3.75%
Expected long-term rate of return on plan assets	1.50%	1.50%	1.50%
10-year expected average return on the index consistent with the Pension Plan's current investment strategy, net of administrative expenses	2.50%
Contributions to plan during the year	$ 0	$ 0	$ 0
Maximum
Assumptions used to determine benefit obligation
Eligible contributions by employer	$ 11,400,000