Accumulated Other Comprehensive Income (Loss) - Schedule of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	$ 1,450,565	$ 1,425,564	$ 1,479,456	$ 1,365,580
Tax effect	(6,608)	16,781	(887)	66,839
Ending Balance	1,443,954	1,396,150	1,443,954	1,396,150
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	35,631	56,880	38,782	61,429
Unrealized gains			210
Amounts reclassified from accumulated other comprehensive income (loss)			(6,027)
Tax effect			1,238
Ending Balance	34,203	$ 49,299	34,203	$ 49,299
Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprehensive Income (Loss)
Beginning Balance			38,783
Amounts reclassified from accumulated other comprehensive income (loss)			(6,018)
Tax effect			1,281
Ending Balance	34,046		34,046
Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss)
Beginning Balance			(1)
Unrealized gains			210
Amounts reclassified from accumulated other comprehensive income (loss)			(9)
Tax effect			(43)
Ending Balance	$ 157		$ 157