Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net Sales	$ 119,437	$ 109,588	$ 233,259	$ 208,670
Cost of sales	89,262	82,003	177,291	165,695
Gross profit	30,175	27,585	55,968	42,975
Selling, general and administrative expenses	13,481	13,086	24,482	23,305
Loss (gain) on disposal of assets	6	(4)	290	(11)
Income from operations	16,688	14,503	31,196	19,681
Interest income, net	31	67	40	135
Other expense, net	17	12	(9)	6
Income before taxes	16,736	14,582	31,227	19,822
Income tax provision	3,775	2,891	7,364	3,871
Net income	$ 12,961	$ 11,691	$ 23,863	$ 15,951
Earnings per share:
Basic (usd per share)	$ 0.25	$ 0.22	$ 0.46	$ 0.30
Diluted (usd per share)	0.25	0.22	0.45	0.30
Cash dividends declared per common share (in dollars per share)	$ 0.16	$ 0.16	$ 0.16	$ 0.16
Weighted average shares outstanding:
Basic (in shares)	52,120,272	52,383,842	52,087,626	52,348,912
Diluted (in shares)	52,747,199	52,717,787	52,589,845	52,754,045