CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Income Statement [Abstract]
Sales	$ 302,713	$ 314,895
Costs, expenses and other:
Costs of goods sold	272,008	266,880
Selling, general and administrative expenses	16,740	19,413
Other non-operating expense (income), net	1,725	1,604
Total costs, expenses and other	290,473	287,897
Income before taxes	12,240	26,998
Income tax expense	3,664	6,824
Net income	$ 8,576	$ 20,174
Earnings per common share
Basic (in dollars per share)	$ 0.31	$ 0.70
Diluted (in dollars per share)	$ 0.31	$ 0.68
Weighted average common shares outstanding
Basic (in shares)	27,942,486	28,820,603
Diluted (in shares)	28,050,955	29,786,957