CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 631,198	$ 478,197	$ 482,763
Other comprehensive (loss) income, before tax:
Foreign currency translation adjustments	142	743	138
Pension and other post-retirement benefit items:
Recognition of previously deferred post-retirement benefit plan costs	4,158	5,217	6,209
Actuarial (loss) gain arising during the period	(21,892)	4,463	22,574
Pension payment timing related charge	300	946	0
Pension and other postretirement benefit items	(17,434)	10,626	28,783
Realized gain on available-for-sale investment during the period	(20,800)	0	0
Unrealized gain on available-for-sale investment during the period	0	20,800	0
Other comprehensive income (loss), before tax	(38,092)	32,169	28,921
Income tax effect related to components of other comprehensive income (loss)	9,775	(8,309)	(7,400)
Other comprehensive income (loss), net of tax	(28,317)	23,860	21,521
Comprehensive income	602,881	502,057	504,284
Comprehensive loss attributable to redeemable non-controlling interest	(729)	(1,242)	15
Total comprehensive income	$ 602,152	$ 500,815	$ 504,299