Statement of Changes in Equity (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended			6 Months Ended
	Jun. 21, 2019	Mar. 22, 2019	Jan. 01, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Cash dividend paid (in dollars per share)	$ 0.35	$ 0.35
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 551,519	$ 554,878		$ 523,378	$ 551,519	$ 992,461
Shares issued under stock-based compensation plans				0		43	0	113
Stock-based compensation expense				70,080		55,844	133,554	91,567
Temporary equity reclassification				1,163		(28,081)	8,110	(28,081)
Common stock issued under employee stock purchase plan							19,016	17,457
Stock repurchases, net				$ (156,195)		(164,978)	$ (250,000)	(914,978)
Accelerated stock repurchase program						$ 150,000		$ 150,000
Restricted shares turned in for tax withholding (in shares)				(104,129)		(30,502)	(698,117)	(537,776)
Restricted shares turned in for tax withholding				$ (10,445)		$ (3,019)	$ (70,551)	$ (49,936)
Other comprehensive income, net of tax				873		(3,844)	3,544	(7,912)
Cash dividends declared				(45,827)			(91,851)
Settlement of convertible notes and hedges				0			0
Cumulative-effect adjustment from adoption of accounting standards			$ 800				838	132,778
Other								1,615
Net income				93,495		106,833	203,843	251,092
Ending balance				$ 508,022	$ 551,519	$ 636,176	$ 508,022	$ 636,176
Beginning balance, treasury shares (in shares)			(178,327,000)				(178,327,000)
Ending balance, treasury shares (in shares)				(186,486,000)	(178,327,000)		(186,486,000)
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)			309,761,000	311,732,000		307,575,000	309,761,000	305,751,000
Shares issued under stock compensation plans (shares)				287,000		87,000	2,042,000	1,659,000
Common stock issued under employee stock purchase plan (shares)							216,000	252,000
Ending balance (in shares)				316,969,000	309,761,000	307,662,000	316,969,000	307,662,000
Beginning balance			$ 310	$ 312		$ 308	$ 310	$ 306
Shares issued under stock-based compensation plans							$ 2	2
Shares issued upon conversion of debt (shares)				(4,950,000)	(1,300,000)		(4,950,000)
Settlement of convertible notes and hedges				$ (5)			$ (5)
Ending balance				317	$ 310	308	317	308
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			5,404,500	5,495,935		4,938,533	5,404,500	4,883,670
Shares issued under stock-based compensation plans						43	(2)	111
Stock-based compensation expense				70,080		55,844	133,554	91,567
Temporary equity reclassification				1,163		(28,081)	8,110	(28,081)
Common stock issued under employee stock purchase plan							19,016	17,457
Accelerated stock repurchase program						150,000		150,000
Settlement of convertible notes and hedges				(509,519)			(509,519)
Other				2,263			4,263	1,615
Ending balance				6,078,960	5,404,500	5,116,339	6,078,960	5,116,339
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			4,169,019	4,232,181		3,786,521	4,169,019	3,509,484
Cash dividends declared				(45,827)			(91,851)
Cumulative-effect adjustment from adoption of accounting standards							838	132,778
Other				(2,263)			(4,263)
Net income				93,495		106,833	203,843	251,092
Ending balance				4,277,586	4,169,019	3,893,354	4,277,586	3,893,354
Accumulated Other Comprehensive Loss [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			(8,154)	(5,483)		(14,874)	(8,154)	(10,806)
Other comprehensive income, net of tax				873		(3,844)	3,544	(7,912)
Ending balance				(4,610)	(8,154)	(18,718)	(4,610)	(18,718)
Common Stock in Treasury [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ (9,014,156)	$ (9,168,067)		$ (8,187,110)	$ (9,014,156)	$ (7,390,193)
Stock repurchases net (shares)				(1,600,000)		(1,783,000)	(2,511,000)	(9,663,000)
Stock repurchases, net				$ (156,195)		$ (164,978)	$ (250,000)	$ (914,978)
Restricted shares turned in for tax withholding (in shares)				104,000		(30,000)	698,000	(537,000)
Restricted shares turned in for tax withholding				$ (10,445)		$ (3,019)	$ (70,551)	$ (49,936)
Shares issued upon conversion of debt (shares)				(4,950,000)			(4,950,000)
Settlement of convertible notes and hedges				$ (509,524)			$ (509,524)
Ending balance				$ (9,844,231)	$ (9,014,156)	$ (8,355,107)	$ (9,844,231)	$ (8,355,107)
Beginning balance, treasury shares (in shares)			(178,327,000)	(179,832,000)		(170,431,000)	(178,327,000)	(162,044,000)
Ending balance, treasury shares (in shares)				(186,486,000)	(178,327,000)	(172,244,000)	(186,486,000)	(172,244,000)