CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Statement [Abstract]
Revenue		$ 725,625	$ 806,338	$ 766,083
Cost of revenue		189,754	206,052	187,289
Gross margin		535,871	600,286	578,794
Research, development, and engineering expenses		119,427	116,445	99,205
Selling, general, and administrative expenses		273,842	262,699	220,728
Operating income		142,602	221,142	258,861
Foreign currency gain (loss)		(509)	(1,064)	(1,601)
Investment income		19,689	14,715	9,542
Other income (expense)		1,212	(219)	(338)
Income before income tax expense		162,994	234,574	266,464
Income tax expense on continuing operations		(40,871)	15,307	89,752
Net income		$ 203,865	$ 219,267	$ 176,712
Net Income per weighted-average common and common-equivalent share (1):
Net income (in dollars per share)		$ 1.19	$ 1.27	$ 1.02
Diluted earnings per weighted-average common and common-equivalent share (1):
Net income (in dollars per share)		$ 1.16	$ 1.24	$ 0.98
Weighted-average common and common-equivalent shares outstanding (1):
Basic (in shares)		171,194	172,333	173,287
Diluted (in shares)		175,269	177,406	179,551
Cash dividends per common share (in dollars per share)	[1]	$ 0.2050	$ 0.1850	$ 0.1675

[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