Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Net sales	$ 383,977	$ 358,632	$ 356,322
Cost of sales	265,897	249,951	248,059
Gross profit	118,080	108,681	108,263
Selling, general and administrative expenses	38,506	37,438	40,562
Gain on disposal of assets	(20)	(59)	(305)
Income from operations	79,594	71,302	68,006
Interest income, net	292	161	276
Other income (expense), net	105	(124)	(36)
Income before taxes	79,991	71,339	68,246
Income tax provision	26,615	25,611	24,088
Net income	$ 53,376	$ 45,728	$ 44,158
Earnings per share:
Basic (usd per share)	$ 1.01	$ 0.85	$ 0.81
Diluted (usd per share)	1.00	0.84	0.80
Cash dividends declared per common share	$ 0.24	$ 0.22	$ 0.18
Weighted average shares outstanding:
Basic	52,924,398	54,045,841	54,809,319
Diluted	53,449,754	54,481,484	55,369,016