Noninterest Income and Noninterest Expense - Net periodic benefit cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Pension Plan
Components of net periodic benefit cost
Interest cost	$ 1,361	$ 1,231	$ 2,722	$ 2,462
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Expected return on plan assets	$ (782)	$ (766)	$ (1,565)	$ (1,532)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Recognized net actuarial loss (gain)	$ 1,269	$ 1,720	$ 2,537	$ 3,440
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Total net periodic benefit cost	$ 1,848	$ 2,185	$ 3,694	$ 4,370
Other Benefits
Components of net periodic benefit cost
Interest cost	$ 143	$ 131	$ 287	$ 262
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Recognized net actuarial loss (gain)	$ (101)		$ (202)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Total net periodic benefit cost	$ 256	$ 395	$ 514	$ 790
Other Benefits | Salaries and employee benefits
Components of net periodic benefit cost
Service cost	$ 214	$ 264	$ 429	$ 528