Accumulated Other Comprehensive Income (Loss) - Schedule of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	$ 1,479,456	$ 1,365,580
Tax effect	3,719	37,138
Ending Balance	1,467,448	1,463,994
Accumulated Other Comprehensive Income (loss)
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	38,782	61,429
Unrealized gains	5
Amounts reclassified from accumulated other comprehensive income	(2,015)
Tax effect	428
Ending Balance	37,200	$ 59,158
Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	38,783
Amounts reclassified from accumulated other comprehensive income	(2,006)
Tax effect	427
Ending Balance	37,204
Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	(1)
Unrealized gains	5
Amounts reclassified from accumulated other comprehensive income	(9)
Tax effect	1
Ending Balance	$ (4)