CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenue		$ 806,338	$ 766,083	$ 529,515
Cost of revenue		206,052	187,289	131,070
Gross margin		600,286	578,794	398,445
Research, development, and engineering expenses		116,445	99,205	78,269
Selling, general, and administrative expenses		262,699	220,728	166,110
Operating income		221,142	258,861	154,066
Foreign currency gain (loss)		(1,064)	(1,601)	101
Investment income		14,715	9,542	7,039
Other income (expense)		(219)	(338)	871
Income from continuing operations before income tax expense		234,574	266,464	162,077
Income tax expense on continuing operations		15,307	89,752	18,128
Net income from continuing operations		219,267	176,712	143,949
Net income (loss) from discontinued operations (Note 20)		0	0	(255)
Net income		$ 219,267	$ 176,712	$ 143,694
Basic earnings per weighted-average common and common-equivalent share (1):
Net income from continuing operations (in dollars per share)		$ 1.27	$ 1.02	$ 0.84
Net income (loss) from discontinued operations (in dollars per share)		0.00	0.00	0.00
Net income (in dollars per share)		1.27	1.02	0.84
Diluted earnings per weighted-average common and common-equivalent share (1):
Net income from continuing operations (in dollars per share)		1.24	0.98	0.83
Net income (loss) from discontinued operations (in dollars per share)		0.00	0.00	0.00
Net income (in dollars per share)		$ 1.24	$ 0.98	$ 0.83
Weighted-average common and common-equivalent shares outstanding (1):
Basic (in shares)		172,333	173,287	170,676
Diluted (in shares)		177,406	179,551	174,144
Cash dividends per common share (in dollars per share)	[1]	$ 0.1850	$ 0.1675	$ 0.1475

[1] Prior period results have been adjusted to reflect the two-for-one stock split effected in the form of a stock dividend which occurred in the fourth quarter of 2017.2