Retirement Plans - Schedule of Net Periodic Benefit Plan (Income) Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Pension Plans
Net periodic benefit plan (income) cost included in other non-interest expense
Interest cost	$ 3,013	$ 983	$ 1,138
Service cost	0	0	0
Return on plan assets	(333)	607	(1,174)
Recognized actuarial (gain) loss	3,831	(630)	765
Amortization of prior service cost	0	0	0
Net periodic benefit plan (income) cost	6,511	960	729
Postretirement Plans
Net periodic benefit plan (income) cost included in other non-interest expense
Interest cost	149	110	133
Service cost	1	0	0
Return on plan assets	0	0	0
Recognized actuarial (gain) loss	(19)	(115)	(248)
Amortization of prior service cost	(46)	(46)	(46)
Net periodic benefit plan (income) cost	$ 85	$ (51)	$ (161)