Stockholders' Equity (Schedule of Treasury Stock) (Details) - USD ($) $ / shares in Units, $ in Millions			9 Months Ended			92 Months Ended
		Sep. 09, 2015	Sep. 30, 2015		Sep. 30, 2014	Sep. 30, 2015
Class of Stock [Line Items]
Shares repurchased			6,640,601	[1]	3,515,301	27,307,796
Average purchase price per share			$ 63.31		$ 57.19	$ 48.90
Cash paid for repurchased shares (in millions)			$ 420		$ 201	$ 1,335
Aggregate Board of Directors repurchase authorizations (in millions)	[2]	$ 1,000	$ 1,000		$ 172	$ 2,366
Restricted Stock [Member]
Class of Stock [Line Items]
Shares withheld, tax withholding			9,264

[1] Excludes 9,264 shares withheld from an executive officer to cover statutory minimum withholding requirements for personal income taxes related to the vesting of restricted stock. Restricted stock awards are considered outstanding at the time of issuance. Accordingly, the shares withheld are treated as treasury shares.

[2] These authorizations give management discretion in determining the timing and conditions under which shares may be repurchased. This repurchase program began in February 2008 and does not have an expiration date. On September 9, 2015, the Board of Directors approved a new $1.0 billion share repurchase authorization.