Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
Net sales	$ 235,537	$ 371,669	$ 566,207	$ 748,360
Cost of sales	147,058	238,306	355,306	482,949
Selling and administrative expenses	78,364	76,406	151,472	157,804
Total operating costs and expenses	225,422	314,712	506,778	640,753
Operating income	10,115	56,957	59,429	107,607
Interest expense	3,898	5,399	8,223	10,512
Other expense (income), net	1,060	1,712	2,654	3,519
Income before income taxes	5,157	49,846	48,552	93,576
Income taxes	4,590	12,230	18,252	21,968
Net income	$ 567	$ 37,616	$ 30,300	$ 71,608
Per common share:
Basic (in dollars per share)	$ 0.01	$ 0.73	$ 0.60	$ 1.39
Diluted (in dollars per share)	$ 0.01	$ 0.73	$ 0.59	$ 1.38
Weighted average common shares outstanding:
Basic (in shares)	50,764,575	51,251,149	50,912,854	51,454,844
Diluted (in shares)	51,008,922	51,743,483	51,200,967	51,965,343