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Equity - Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Apr. 01, 2018	Jan. 01, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	$ 963,802	$ 921,432	$ 850,757	$ 983,465
Net income	41,388	11,753	165,589	38,436
Other comprehensive income (loss)	(7,785)	1,367	(41,397)	(24,783)
Issuances under stock plans	4,171	3,463	13,248	6,529
Common share repurchases	(94,873)	(7,186)	(126,433)	(104,400)
Stock-based compensation expense	12,954	10,718	57,893	56,018
Ending balance	919,657	941,548	919,657	941,548
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	1,868,878	1,798,075	1,823,710	1,761,383
Issuances under stock plans	3,538	1,752	3,767	(6,856)
Stock-based compensation expense	12,954	10,718	57,893	56,018
Ending balance	1,885,370	1,810,545	1,885,370	1,810,545
Accumulated Other Comprehensive Loss, Net
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(73,479)	(24,051)	(39,867)	1,508
Other comprehensive income (loss)	(7,785)	1,367	(41,397)	(24,783)
Ending balance	(81,264)	(22,684)	(81,264)	(22,684)
Accumulated Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	1,879,633	1,659,658	1,755,432	1,647,284
Net income	41,388	11,753	165,589	38,436
Ending balance	1,921,021	1,671,412	1,921,021	1,671,412
Treasury Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	(2,711,312)	(2,512,332)	(2,688,600)	(2,426,792)
Issuances under stock plans	633	1,711	9,481	13,385
Common share repurchases	(94,873)	(7,186)	(126,433)	(104,400)
Ending balance	$ (2,805,552)	$ (2,517,807)	$ (2,805,552)	$ (2,517,807)
Accounting Standards Update 2018-02
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU					$ 0
Accounting Standards Update 2018-02 \| Accumulated Other Comprehensive Loss, Net
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU					591
Accounting Standards Update 2018-02 \| Accumulated Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU					$ (591)
Accounting Standards Update 2016-16
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU						$ (13,717)
Accounting Standards Update 2016-16 \| Accumulated Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU						$ (13,717)