Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Net sales	$ 216,665	$ 207,910	$ 393,156	$ 376,198
Cost of sales	118,347	111,993	217,340	202,518
Gross profit	98,318	95,917	175,816	173,680
Operating expenses:
Research and development and other engineering	10,517	10,094	20,713	19,794
Selling	23,013	24,213	45,620	46,032
General and administrative	29,794	29,511	58,227	56,435
Gain on sale of assets	(15)	(34)	(30)	(319)
Total operating expenses	63,309	63,784	124,530	121,942
Income from operations	35,009	32,133	51,286	51,738
Interest (expense) income, net	(54)	(15)	(89)	71
Income before taxes	34,955	32,118	51,197	51,809
Provision for income taxes	13,446	11,667	19,637	19,271
Net income	$ 21,509	$ 20,451	$ 31,560	$ 32,538
Earnings per common share:
Basic (in dollars per share)	$ 0.44	$ 0.42	$ 0.64	$ 0.66
Diluted (in dollars per share)	$ 0.43	$ 0.42	$ 0.64	$ 0.66
Number of shares outstanding
Basic (in shares)	49,254	49,011	49,236	48,955
Diluted (in shares)	49,473	49,227	49,445	49,146
Cash dividends declared per common share (in dollars per share)	$ 0.16	$ 0.14	$ 0.3	$ 0.265