Consolidated Statement of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Net sales	$ 723,530	$ 705,030	$ 656,160
Cost of sales	(529,630)	(504,920)	(466,880)
Gross profit	193,900	200,110	189,280
Selling, general and administrative expenses	(102,530)	(91,210)	(99,900)
Net gain (loss) on dispositions of assets	(150)	(90)	3,340
Operating profit	91,220	108,810	92,720
Other expense, net:
Interest expense	(13,950)	(13,910)	(14,390)
Other income (expense), net	990	(2,540)	(8,450)
Other expense, net	(12,960)	(16,450)	(22,840)
Income before income taxes	78,260	92,360	69,880
Income tax expense	(16,320)	(18,650)	(33,920)
Income from continuing operations	61,940	73,710	35,960
Income (loss) from discontinued operations, net of income taxes	36,680	9,590	(5,000)
Net income	$ 98,620	$ 83,300	$ 30,960
Basic earnings (loss) per share:
Continuing operations	$ 1.37	$ 1.61	$ 0.79
Discontinued operations	0.81	0.21	(0.11)
Net income per share	$ 2.18	$ 1.82	$ 0.68
Weighted average common shares—basic	45,303,659	45,824,555	45,682,627
Diluted earnings (loss) per share:
Continuing operations	$ 1.36	$ 1.60	$ 0.78
Discontinued operations	0.80	0.20	(0.11)
Net income per share	$ 2.16	$ 1.80	$ 0.67
Weighted average common shares—diluted	45,595,154	46,170,464	45,990,252