Statement of Changes in Equity (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended			9 Months Ended
	Sep. 20, 2019	Jun. 21, 2019	Mar. 22, 2019	Jan. 01, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Cash dividend paid (in dollars per share)	$ 0.35	$ 0.35	$ 0.35
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				$ 551,519	$ 508,022	$ 753,220	$ 636,176	$ 551,519	$ 992,461
Shares issued under stock-based compensation plans					0		50	0	164
Stock-based compensation expense					68,969		52,739	202,523	145,920
Temporary equity reclassification							8,796	8,110	(19,286)
Common stock issued under employee stock purchase plan					20,455		16,004	39,471	33,462
Stock repurchases, net					$ (103,905)		$ (116,175)	$ (353,904)	$ (881,154)
Restricted shares turned in for tax withholding (in shares)					(44,829)		(32,813)	(742,946)	(570,589)
Restricted shares turned in for tax withholding					$ (4,242)		$ (3,654)	$ (74,794)	$ (53,589)
Other comprehensive income, net of tax					(1,872)		427	1,672	(7,485)
Cash dividends declared					$ (45,373)			(137,224)
Settlement of convertible notes and hedges								0
Settlement of warrants (in shares)					200,000
Cumulative-effect adjustment from adoption of accounting standards				$ 800				838	132,778
Net income					$ 270,857		158,857	474,700	409,949
Ending balance					$ 712,911	$ 551,519	$ 753,220	$ 712,911	$ 753,220
Beginning balance, treasury shares (in shares)				(178,327,000)				(178,327,000)
Ending balance, treasury shares (in shares)					(187,661,000)	(178,327,000)		(187,661,000)
Common Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance (in shares)				309,761,000	316,969,000	307,981,000	307,662,000	309,761,000	305,751,000
Shares issued under stock compensation plans (shares)					123,000		110,000	2,167,000	1,769,000
Common stock issued under employee stock purchase plan (shares)					255,000		209,000	471,000	461,000
Ending balance (in shares)					317,549,000	309,761,000	307,981,000	317,549,000	307,981,000
Beginning balance				$ 310	$ 317	$ 308	$ 308	$ 310	$ 306
Shares issued under stock-based compensation plans								$ 2	2
Common stock issued under employee stock purchase plan					$ 1
Shares issued upon conversion of debt (shares)						(1,300,000)		(4,950,000)
Settlement of convertible notes and hedges								$ (5)
Settlement of warrants (in shares)					202,000			202,000
Other								(2,000)
Ending balance					$ 318	$ 310	308	$ 318	308
Additional Paid-in Capital [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				5,404,500	6,078,960	5,193,928	5,116,339	5,404,500	4,883,670
Shares issued under stock-based compensation plans							50	(2)	162
Stock-based compensation expense					68,969		52,739	202,523	145,920
Temporary equity reclassification							8,796	8,110	(19,286)
Common stock issued under employee stock purchase plan					20,454		16,004	39,470	33,462
Accelerated stock repurchase program									150,000
Settlement of convertible notes and hedges								(509,519)
Other					2,194			6,457
Ending balance					6,170,577	5,404,500	5,193,928	6,170,577	5,193,928
Retained Earnings [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				4,169,019	4,277,586	4,052,211	3,893,354	4,169,019	3,509,484
Cash dividends declared					(45,373)			(137,224)
Cumulative-effect adjustment from adoption of accounting standards								838	132,778
Other					(2,194)			(6,457)
Net income					270,857		158,857	474,700	409,949
Ending balance					4,500,876	4,169,019	4,052,211	4,500,876	4,052,211
Accumulated Other Comprehensive Loss [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				(8,154)	(4,610)	(18,291)	(18,718)	(8,154)	(10,806)
Other comprehensive income, net of tax					(1,872)		427	1,672	(7,485)
Ending balance					(6,482)	(8,154)	(18,291)	(6,482)	(18,291)
Common Stock in Treasury [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance				$ (9,014,156)	$ (9,844,231)	(8,474,936)	$ (8,355,107)	$ (9,014,156)	$ (7,390,193)
Stock repurchases net (shares)					(1,130,000)		(1,046,000)	(3,641,000)	(10,708,000)
Stock repurchases, net					$ (103,905)		$ (116,175)	$ (353,904)	$ (1,031,154)
Restricted shares turned in for tax withholding (in shares)					(45,000)		(32,000)	(743,000)	(570,000)
Restricted shares turned in for tax withholding					$ (4,242)		$ (3,654)	$ (74,794)	$ (53,589)
Shares issued upon conversion of debt (shares)								(4,950,000)
Settlement of convertible notes and hedges								$ (509,524)
Ending balance					$ (9,952,378)	$ (9,014,156)	$ (8,474,936)	$ (9,952,378)	$ (8,474,936)
Beginning balance, treasury shares (in shares)				(178,327,000)	(186,486,000)	(173,322,000)	(172,244,000)	(178,327,000)	(162,044,000)
Ending balance, treasury shares (in shares)					(187,661,000)	(178,327,000)	(173,322,000)	(187,661,000)	(173,322,000)