Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Net sales	$ 376,692	$ 366,660
Cost of sales	244,643	237,134
Selling and administrative expenses	81,400	72,893
Total operating costs and expenses	326,043	310,027
Operating income	50,649	56,633
Interest expense	5,113	3,892
Other expense (income), net	1,806	1,763
Income before income taxes	43,730	50,978
Income taxes	9,738	12,160
Net income	$ 33,992	$ 38,818
Per common share:
Basic (in dollars per share)	$ 0.66	$ 0.73
Diluted (in dollars per share)	$ 0.65	$ 0.72
Weighted average common shares outstanding:
Basic (in shares)	51,660,804	53,535,424
Diluted (in shares)	52,189,465	54,089,327