Consolidated Statements Of Equity - USD ($) $ in Thousands	Total	Common Stock	Treasury Stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive (Loss) Income	Non- controlling Interest
Beginning balance (in shares) at Dec. 31, 2016		53,251,805	102,774
Beginning balance at Dec. 31, 2016	$ 1,557,724	$ 5	$ (8,946)	$ 650,974	$ 1,094,108	$ (178,583)	$ 166
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of RSU's and PSU's (in shares)		617,662
Exercise of stock options and vesting of RSU's and PSU's	25,062			25,062
Common stock issued under employee stock purchase plan (in shares)		35,467
Common stock issued under employee stock purchase plan	3,592			3,592
Purchased common stock (in shares)		(275,495)	(275,495)
Purchased common stock	(39,987)		$ (39,987)
Stock-based compensation	23,021			23,021
Purchase of non-controlling interest	(197)						(197)
Net income	347,588				347,614		(26)
Foreign currency translation adjustments	101,056					100,999	57
Unrealized gain on derivatives, net of tax	(58)					(58)
Unrealized loss on available-for-sale investments, net of tax	(240)					(240)
Unrealized loss on available-for-sale investments, net of tax	538					538
Ending balance (in shares) at Dec. 31, 2017		53,629,439	378,269
Ending balance at Dec. 31, 2017	2,022,322	$ 5	$ (48,933)	704,727	1,443,867	(77,344)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of RSU's and PSU's (in shares)		351,795
Exercise of stock options and vesting of RSU's and PSU's	9,895			9,895
Common stock issued under employee stock purchase plan (in shares)		12,198
Common stock issued under employee stock purchase plan	2,288			2,288
Purchased common stock (in shares)		(1,051,825)	(1,051,825)
Purchased common stock	(176,065)		$ (176,065)
Stock-based compensation	28,027			28,027
Purchase of non-controlling interest	558						558
Net income	404,169				404,027		142
Foreign currency translation adjustments	(85,590)					(85,577)	(13)
Unrealized loss on available-for-sale investments, net of tax	0
Unrealized loss on available-for-sale investments, net of tax	0
Unrealized loss on derivatives, net of tax	15					15
Ending balance (in shares) at Dec. 31, 2018		52,941,607	1,430,094
Ending balance at Dec. 31, 2018	2,206,235	$ 5	$ (224,998)	744,937	1,848,500	(162,896)	687
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options and vesting of RSU's and PSU's (in shares)		319,211
Exercise of stock options and vesting of RSU's and PSU's	805			805
Common stock issued under employee stock purchase plan (in shares)		52,315
Common stock issued under employee stock purchase plan	6,531			6,531
Purchased common stock (in shares)		(302,258)	(302,258)
Purchased common stock	(40,732)		$ (40,732)
Stock-based compensation	33,363			33,363
Net income	180,261				180,234		27
Foreign currency translation adjustments	15,997					15,994	3
Unrealized loss on available-for-sale investments, net of tax	0
Unrealized loss on available-for-sale investments, net of tax	0
Unrealized loss on derivatives, net of tax	(17)					(17)
Ending balance (in shares) at Dec. 31, 2019		53,010,875	1,732,352
Ending balance at Dec. 31, 2019	$ 2,402,443	$ 5	$ (265,730)	$ 785,636	$ 2,028,734	$ (146,919)	$ 717