Benefit Plans - Net periodic benefit cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Components of net periodic benefit cost
Interest cost	$ 3,643	$ 2,466	$ 2,261
Expected return on plan assets	(3,534)	(3,124)	(3,044)
Recognized net actuarial loss (gain)	2,818	1,906	1,609
Total net periodic benefit cost	$ 2,927	$ 1,248	$ 826
Defined Benefit Plan, Funding Status [Extensible Enumeration]	Funded Plan	Funded Plan	Funded Plan
Pension Plan
Components of net periodic benefit cost
Interest cost	$ 8,275	$ 5,518	$ 5,065
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
Expected return on plan assets	$ (3,534)	$ (3,124)	$ (3,044)
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
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Recognized net actuarial loss (gain)	$ 2,818	$ 5,643	$ 6,961
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
Total net periodic benefit cost	$ 7,559	$ 8,037	$ 8,982
Other Benefits
Components of net periodic benefit cost
Service cost	545	789
Interest cost	$ 844	$ 565	$ 515
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
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Noninterest Expense	Other Noninterest Expense	Other Noninterest Expense
Recognized net actuarial loss (gain)	$ (1,676)	$ (497)	$ (48)
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
Total net periodic benefit cost	$ (287)	$ 857	$ 1,341
Other Benefits | Salaries and employee benefits
Components of net periodic benefit cost
Service cost	$ 545	$ 789	$ 874