Stockholders' Equity (Schedule of Treasury Stock) (Details) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended			80 Months Ended
	Sep. 30, 2014	Sep. 30, 2013		Sep. 30, 2014		Feb. 06, 2014	Oct. 18, 2012	Apr. 25, 2011	Oct. 23, 2008	Feb. 08, 2008
Class of Stock [Line Items]
Share repurchase plan, authorized repurchase amount	$ 1,065			$ 1,065		$ 172	$ 264	$ 129	$ 100	$ 400
Shares repurchased	3,515,301	2,096,320	[1]	19,844,008	[2]
Average purchase price per share	$ 57.19	$ 48.58		$ 43.64
Amount spent on repurchased shares (in millions)	$ 201	$ 102		$ 866
Restricted Stock [Member]
Class of Stock [Line Items]
Shares withheld, tax withholding		6,021		11,844

[1] Excludes 6,021 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] Excludes 11,844 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.