Accumulated Other Comprehensive Income (Loss) - Schedule of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	$ 1,463,994	$ 924,252	$ 1,365,580	$ 683,866
Tax effect	12,920	496	50,058	951
Ending Balance	1,425,564	1,188,708	1,425,564	1,188,708
Accumulated Other Comprehensive Income (loss)
Accumulated Other Comprehensive Income (Loss)
Beginning Balance	59,158	15,581	61,429	14,158
Unrealized (losses)			(60)
Amounts reclassified from accumulated other comprehensive income (loss)			(5,769)
Tax effect			1,280
Ending Balance	56,880	$ 6,680	56,880	$ 6,680
Pension, Postretirement and Other Post-Employment Benefits
Accumulated Other Comprehensive Income (Loss)
Beginning Balance			61,485
Amounts reclassified from accumulated other comprehensive income (loss)			(5,790)
Tax effect			1,272
Ending Balance	56,967		56,967
Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss)
Beginning Balance			(56)
Unrealized (losses)			(60)
Amounts reclassified from accumulated other comprehensive income (loss)			21
Tax effect			8
Ending Balance	$ (87)		$ (87)