Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss, Net	Accumulated Earnings	Treasury Stock
Beginning balance at Dec. 31, 2018	$ 850,757	$ 82	$ 1,823,710	$ (39,867)	$ 1,755,432	$ (2,688,600)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	20,795				20,795
Other comprehensive income (loss)	(21,699)			(21,699)
Issuances under stock plans	5,062		(2,911)			7,973
Common share repurchases	(29,837)					(29,837)
Stock-based compensation expense	31,819		31,819
Ending balance at Mar. 31, 2019	856,897	82	1,852,618	(61,566)	1,776,227	(2,710,464)
Beginning balance at Dec. 31, 2018	850,757	82	1,823,710	(39,867)	1,755,432	(2,688,600)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	165,589
Other comprehensive income (loss)	(41,397)
Ending balance at Sep. 30, 2019	919,657	82	1,885,370	(81,264)	1,921,021	(2,805,552)
Beginning balance at Mar. 31, 2019	856,897	82	1,852,618	(61,566)	1,776,227	(2,710,464)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	103,406				103,406
Other comprehensive income (loss)	(11,913)			(11,913)
Issuances under stock plans	4,015		3,140			875
Common share repurchases	(1,723)					(1,723)
Stock-based compensation expense	13,120		13,120
Ending balance at Jun. 30, 2019	963,802	82	1,868,878	(73,479)	1,879,633	(2,711,312)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	41,388				41,388
Other comprehensive income (loss)	(7,785)			(7,785)
Issuances under stock plans	4,171		3,538			633
Common share repurchases	(94,873)					(94,873)
Stock-based compensation expense	12,954		12,954
Ending balance at Sep. 30, 2019	919,657	82	1,885,370	(81,264)	1,921,021	(2,805,552)
Beginning balance at Dec. 31, 2019	938,593	82	1,899,273	(77,938)	1,988,722	(2,871,546)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	75,097				75,097
Other comprehensive income (loss)	(91,034)			(91,034)
Issuances under stock plans	5,654		(1,794)			7,448
Common share repurchases	(63,164)					(63,164)
Stock-based compensation expense	25,129		25,129
Ending balance at Mar. 31, 2020	890,275	82	1,922,608	(168,972)	2,063,819	(2,927,262)
Beginning balance at Dec. 31, 2019	938,593	82	1,899,273	(77,938)	1,988,722	(2,871,546)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	147,138
Other comprehensive income (loss)	(52,275)
Ending balance at Sep. 30, 2020	1,037,503	82	1,960,143	(130,213)	2,135,860	(2,928,369)
Beginning balance at Mar. 31, 2020	890,275	82	1,922,608	(168,972)	2,063,819	(2,927,262)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	55,077				55,077
Other comprehensive income (loss)	26,797			26,797
Issuances under stock plans	4,090		3,223			867
Common share repurchases	(698)					(698)
Stock-based compensation expense	15,678		15,678
Ending balance at Jun. 30, 2020	991,219	82	1,941,509	(142,175)	2,118,896	(2,927,093)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,964				16,964
Other comprehensive income (loss)	11,962			11,962
Issuances under stock plans	4,112		3,133			979
Common share repurchases	(2,255)					(2,255)
Stock-based compensation expense	15,501		15,501
Ending balance at Sep. 30, 2020	$ 1,037,503	$ 82	$ 1,960,143	$ (130,213)	$ 2,135,860	$ (2,928,369)