CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue	$ 520,753	$ 450,557	$ 426,449
Cost of revenue	115,590	102,571	94,067
Gross margin	405,163	347,986	332,382
Research, development, and engineering expenses	78,269	69,791	55,831
Selling, general, and administrative expenses	166,110	156,674	148,699
Operating income	160,784	121,521	127,852
Foreign currency gain (loss)	101	1,122	1,031
Investment income	7,039	3,674	3,156
Other income (expense)	871	645	(283)
Income from continuing operations before income tax expense	168,795	126,962	131,756
Income tax expense on continuing operations	18,968	19,298	20,915
Net income from continuing operations	149,827	107,664	110,841
Net income (loss) from discontinued operations (Note 19)	(255)	79,410	10,644
Net income	$ 149,572	$ 187,074	$ 121,485
Basic earnings per weighted-average common and common-equivalent share:
Net income from continuing operations (in dollars per share)	$ 1.76	$ 1.25	$ 1.28
Net income from discontinued operations (in dollars per share)	(0.01)	0.92	0.12
Net income (in dollars per share)	1.75	2.17	1.40
Diluted earnings per weighted-average common and common-equivalent share:
Net income from continuing operations (in dollars per share)	1.72	1.22	1.24
Net income from discontinued operations (in dollars per share)	0.00	0.91	0.12
Net income (in dollars per share)	$ 1.72	$ 2.13	$ 1.36
Weighted-average common and common-equivalent shares outstanding:
Basic (in shares)	85,338	86,296	86,858
Diluted (in shares)	87,072	87,991	89,071
Cash dividends per common share (in dollars per share)	$ 0.30	$ 0.21	$ 0.00