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Equity - Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Apr. 01, 2018	Jan. 01, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 856,897	$ 987,571	$ 850,757	$ 983,465
Net income	103,406	46,270	124,201	26,683
Other comprehensive income (loss)	(11,913)	(56,867)	(33,612)	(26,150)
Issuances under stock plans	4,015	(1,077)	9,077	3,066
Common share repurchases	(1,723)	(68,806)	(31,560)	(97,214)
Stock-based compensation expense	13,120	14,342	44,939	45,300
Ending balance	963,802	921,432	963,802	921,432
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	82	82	82	82
Ending balance	82	82	82	82
Additional Paid-In Capital
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,852,618	1,788,045	1,823,710	1,761,383
Issuances under stock plans	3,140	(4,312)	229	(8,608)
Stock-based compensation expense	13,120	14,342	44,939	45,300
Ending balance	1,868,878	1,798,075	1,868,878	1,798,075
Accumulated Other Comprehensive Income (Loss), Net
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(61,566)	32,225	(39,867)	1,508
Other comprehensive income (loss)	(11,913)	(56,867)	(33,612)	(26,150)
Ending balance	(73,479)	(24,051)	(73,479)	(24,051)
Accumulated Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,776,227	1,613,980	1,755,432	1,647,284
Net income	103,406	46,270	124,201	26,683
Ending balance	1,879,633	1,659,658	1,879,633	1,659,658
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2,710,464)	(2,446,761)	(2,688,600)	(2,426,792)
Issuances under stock plans	875	3,235	8,848	11,674
Common share repurchases	(1,723)	(68,806)	(31,560)	(97,214)
Ending balance	$ (2,711,312)	$ (2,512,332)	$ (2,711,312)	$ (2,512,332)
Accounting Standards Update 2018-02 \| Accumulated Other Comprehensive Income (Loss), Net
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption Of ASU No					$ 591	$ 591
Accounting Standards Update 2018-02 \| Accumulated Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption Of ASU No					$ (591)
Accounting Standards Update 2016-16
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption Of ASU No						(13,717)
Accounting Standards Update 2016-16 \| Accumulated Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption Of ASU No						$ (13,717)