Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Income Statement [Abstract]
Revenues		$ 411,350	$ 354,193
Costs and expenses:
Cost of goods sold		179,847	169,302
Selling, general and administrative expenses		16,294	16,758
Net loss on fire damage		276
Total costs and expenses		196,417	186,060
Operating income		214,933	168,133
Interest expense, net	[1]	(2,894)	(3,574)
Pension settlement charge		(14,165)
Non-operating pension and other postretirement employee benefit costs		(1,929)	(3,414)
Income before income taxes		195,945	161,145
Income taxes		(32,065)	(30,039)
Net income		$ 163,880	$ 131,106
Net income per share:
Basic		$ 2.36	$ 1.95
Diluted		2.35	1.94
Dividends per share		$ 0.44	$ 0.41
Weighted-average shares outstanding (in thousands)
Basic		69,419	67,207
Diluted		69,623	67,607

[1] Bond discounts and deferred loan fees are reported within interest expense, net on the Condensed Consolidated Statements of Operations.