Consolidated Statements Of Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common stock	Additional paid-in capital	Retained earnings (deficit)	Foreign currency translation adjustments	Available-for-sale investments-Change in net unrealized gains	Defined benefit pension adjustments
Balance (in shares) at Dec. 31, 2014		139,793
Balance at Dec. 31, 2014	$ 748,441	$ 1,398	$ 830,430	$ (80,712)	$ (1,668)	$ 0	$ (1,007)
Shares issued under stock plans (in shares)		923
Shares issued under stock plans	1,756	$ 9	1,747	0	0	0	0
Share-based compensation expense	11,033	0	11,033	0	0	0	0
Tax benefit associated with stock plans	5,457	0	5,457	0	0	0	0
Pension liability adjustment	(142)	0	0	0	0	0	(142)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0
Unrealized gain on available-for-sale investments	611	0	0	0	0	611	0
Foreign currency translation	(44,569)	0	0	0	(44,569)	0	0
Reclassification of cumulative translation adjustment associated with liquidated and planned sale of subsidiaries	0
Net income	80,296	$ 0	0	80,296	0	0	0
Balance (in shares) at Dec. 31, 2015		140,716
Balance at Dec. 31, 2015	802,883	$ 1,407	848,667	(416)	(46,237)	611	(1,149)
Shares issued under stock plans (in shares)		1,123
Shares issued under stock plans	826	$ 11	815	0	0	0	0
Share-based compensation expense	13,436	$ 0	13,436	0	0	0	0
Repurchase and retirement of common stock (in shares)		(519)
Repurchase and retirement of common stock	(7,573)	$ (5)	(3,140)	(4,428)	0	0	0
Pension liability adjustment	462	0	0	0	0	0	462
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(611)	0	0	0	0	(611)	0
Unrealized gain on available-for-sale investments	0
Foreign currency translation	(7,352)	0	0	0	(7,352)	0	0
Reclassification of cumulative translation adjustment associated with liquidated and planned sale of subsidiaries	0
Net income	97,147	$ 0	0	97,147	0	0	0
Balance (in shares) at Dec. 31, 2016		141,320
Balance at Dec. 31, 2016	899,218	$ 1,413	859,778	92,303	(53,589)	0	(687)
Shares issued under stock plans (in shares)		1,040
Shares issued under stock plans	(321)	$ 11	(332)	0	0	0	0
Share-based compensation expense	15,306	$ 0	15,306	0	0	0	0
Repurchase and retirement of common stock (in shares)		(1,077)
Repurchase and retirement of common stock	(28,000)	$ (11)	(6,565)	(21,424)
Dividends, Common Stock, Cash	(9,896)	0	0	(9,896)	0	0	0
Pension liability adjustment	(232)	0	0	0	0	0	(232)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0
Unrealized gain on available-for-sale investments	0
Foreign currency translation	29,294	0	0	0	29,294	0	0
Reclassification of cumulative translation adjustment associated with liquidated and planned sale of subsidiaries	1,702	0	0	0	1,702	0	0
Net income	85,066	$ 0	0	85,066	0	0	0
Balance (in shares) at Dec. 31, 2017		141,283
Balance at Dec. 31, 2017	993,018	$ 1,413	867,699	147,418	(22,593)	0	(919)
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 881	$ 0	$ (488)	$ 1,369	$ 0	$ 0	$ 0