Stockholders' Equity (Schedule of Treasury Stock) (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended					3 Months Ended		74 Months Ended
	Feb. 28, 2014	Oct. 31, 2012	Apr. 30, 2011	Oct. 31, 2008	Feb. 29, 2008	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Class of Stock [Line Items]
Share repurchase plan, authorized repurchase amount	$ 172	$ 264	$ 129	$ 100	$ 400			$ 1,065
Shares repurchased						1,035,374	0	17,364,081	[1]
Average purchase price per share						$ 51.30	$ 0	$ 41.36
Amount spent on repurchased shares						$ 53	$ 0	$ 718
Restricted Stock [Member]
Class of Stock [Line Items]
Shares withheld, tax withholding								11,844

[1] 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 and therefore, the shares withheld are treated as treasury shares.