Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 357,156	$ 311,561	$ 1,063,451	$ 906,586
Cost of sales	236,016	198,600	692,355	582,028
Selling and administrative expenses	73,354	61,144	210,423	183,754
Total operating costs and expenses	309,370	259,744	902,778	765,782
Operating income	47,786	51,817	160,673	140,804
Interest expense	3,748	3,020	10,638	8,826
Other expense (income), net	357	621	773	24
Income before income taxes	43,681	48,176	149,262	131,954
Income taxes	8,348	11,348	30,599	33,066
Net income	$ 35,333	$ 36,828	$ 118,663	$ 98,888
Per common share:
Basic (in dollars per share)	$ 0.65	$ 0.68	$ 2.19	$ 1.82
Diluted (in dollars per share)	0.65	0.67	2.17	1.81
Dividends (in dollars per share)	$ 0.14	$ 0.13	$ 0.41	$ 0.38
Weighted average common shares outstanding:
Basic (in shares)	54,066,509	54,206,064	54,140,551	54,206,798
Diluted (in shares)	54,570,677	54,572,315	54,649,723	54,643,739