Noninterest Income and Noninterest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Leases
Operating lease income	$ 1,500	$ 1,500
Lease income related to variable lease payments	1,500	1,100
Pension Benefits
Components of net periodic benefit cost
Total net periodic benefit cost	1,856	2,430
Pension Benefits | Salaries and employee benefits
Components of net periodic benefit cost
Service cost		17
Pension Benefits | Other noninterest expense
Components of net periodic benefit cost
Interest cost	1,621	2,044
Expected return on plan assets	(1,194)	(1,195)
Recognized net actuarial loss (gain)	1,429	1,564
Other Benefits
Components of net periodic benefit cost
Total net periodic benefit cost	314	182
Other Benefits | Salaries and employee benefits
Components of net periodic benefit cost
Service cost	189	159
Other Benefits | Other noninterest expense
Components of net periodic benefit cost
Interest cost	164	206
Prior service credit	(13)	(107)
Recognized net actuarial loss (gain)	$ (26)	$ (76)