CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 747,950	$ 520,753	$ 450,557
Cost of revenue	168,698	115,590	102,571
Gross margin	579,252	405,163	347,986
Research, development, and engineering expenses	99,205	78,269	69,791
Selling, general, and administrative expenses	220,728	166,110	156,674
Operating income	259,319	160,784	121,521
Foreign currency gain (loss)	(1,601)	101	1,122
Investment income	9,542	7,039	3,674
Other income (expense)	(338)	871	645
Income from continuing operations before income tax expense	266,922	168,795	126,962
Income tax expense on continuing operations	89,744	18,968	19,298
Net income from continuing operations	177,178	149,827	107,664
Net income (loss) from discontinued operations (Note 19)	0	(255)	79,410
Net income	$ 177,178	$ 149,572	$ 187,074
Basic earnings per weighted-average common and common-equivalent share (1):
Net income from continuing operations (in dollars per share)	$ 1.02	$ 0.88	$ 0.62
Net income from discontinued operations (in dollars per share)	0.00	0.00	0.46
Net income (in dollars per share)	1.02	0.88	1.08
Diluted earnings per weighted-average common and common-equivalent share (1):
Net income from continuing operations (in dollars per share)	0.99	0.86	0.61
Net income from discontinued operations (in dollars per share)	0.00	0.00	0.45
Net income (in dollars per share)	$ 0.99	$ 0.86	$ 1.06
Weighted-average common and common-equivalent shares outstanding (1):
Basic (in shares)	173,287	170,676	172,592
Diluted (in shares)	179,551	174,144	175,982
Cash dividends per common share (in dollars per share)	$ 0.17	$ 0.15	$ 0.11