Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 1,495,889	$ 1,436,499	$ 1,230,754
Cost of sales	963,524	943,779	788,727
Selling and administrative expenses	300,601	286,269	247,731
Total operating costs and expenses	1,264,125	1,230,048	1,036,458
Operating income	231,764	206,451	194,296
Interest expense	16,841	14,571	11,883
Other expense (income), net	7,428	(3,819)	(208)
Income before income taxes	207,495	195,699	182,621
Income taxes	41,309	136,284	47,020
Net income	$ 166,186	$ 59,415	$ 135,601
Per common share:
Basic (in dollars per share)	$ 3.18	$ 1.10	$ 2.50
Diluted (in dollars per share)	3.15	$ 1.09	2.48
Dividends (in dollars per share)	$ 0.62		$ 0.51
Weighted average common shares outstanding:
Basic (in shares)	52,304,190	54,073,407	54,191,013
Diluted (in shares)	52,831,606	54,605,298	54,631,313