Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Revenues		$ 208,880	$ 181,716
Costs and expenses:
Cost of goods sold		172,046	154,215
Selling, general and administrative expenses		14,207	16,570
Gain on sale of facility			(9,176)
Total costs and expenses		186,253	161,609
Operating income		22,627	20,107
Interest expense, net	[1]	(3,698)	(5,464)
Loss on extinguishment of debt			(5,512)
Pension settlement charge		(42,988)
Non-operating pension and other postretirement employee benefit costs		(3,635)	(980)
(Loss) income before income taxes		(27,694)	8,151
Income taxes		10,862	(1,591)
Net (loss) income		$ (16,832)	$ 6,560
Net (loss) income per share:
Basic (in dollars per share)		$ (0.25)	$ 0.10
Diluted (in dollars per share)		(0.25)	0.10
Dividends per share (in dollars per share)		$ 0.40	$ 0.40
Weighted-average shares outstanding:
Basic (in shares)		67,478	67,860
Diluted (in shares)		67,478	67,916

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