Noninterest Income and Noninterest Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating lease income related to lease payments
Operating lease income	$ 1,700	$ 1,500
Lease income related to variable lease payments	1,500	1,500
Pension Benefits
Components of net periodic benefit cost
Total net periodic benefit cost	2,185	1,856
Pension Benefits | Other noninterest expense
Components of net periodic benefit cost
Interest cost	1,231	1,621
Expected return on plan assets	(766)	(1,194)
Recognized net actuarial loss (gain)	1,720	1,429
Other Benefits
Components of net periodic benefit cost
Total net periodic benefit cost	395	314
Other Benefits | Salaries and employee benefits
Components of net periodic benefit cost
Service cost	264	189
Other Benefits | Other noninterest expense
Components of net periodic benefit cost
Interest cost	$ 131	164
Prior service credit		(13)
Recognized net actuarial loss (gain)		$ (26)