Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ 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	$ 304,853	$ 308,007	$ 564,097	$ 552,786
Cost of sales	170,674	167,442	319,664	304,599
Gross profit	134,179	140,565	244,433	248,187
Operating expenses:
Research and development and other engineering	11,055	11,249	23,316	22,399
Selling	28,687	29,201	56,799	56,774
General and administrative	41,345	38,807	80,893	76,206
Total operating expenses	81,087	79,257	161,008	155,379
Net gain on disposal of assets	(561)	(125)	(251)	(1,309)
Income from operations	53,653	61,433	83,676	94,117
Interest income (expense), net and other	147	(871)	(616)	(873)
Income before taxes	53,800	60,562	83,060	93,244
Provision for income taxes	14,223	16,476	20,821	23,729
Net income	39,577	44,086	62,239	69,515
Translation adjustment	(1,363)	11,442	(28)	7,583
Unamortized pension adjustments	(100)	0	(100)	0
Comprehensive net income	$ 40,840	$ 32,644	$ 62,167	$ 61,932
Earnings per common share:
Basic	$ 0.89	$ 0.95	$ 1.39	$ 1.50
Diluted	$ 0.88	$ 0.94	$ 1.38	$ 1.48
Number of shares outstanding
Basic	44,671	46,323	44,772	46,468
Diluted	44,972	46,677	45,089	46,842
Cash dividends declared per common share (in dollars per share)	$ 0.23	$ 0.22	$ 0.45	$ 0.43