Stockholders' Equity (Schedule of Share Repurchase Plan Authorization) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
Apr. 30, 2011	Oct. 31, 2008	Feb. 29, 2008	Dec. 31, 2011
Stockholders' Equity Note [Abstract]
Share Repurchase Plan, Authorized Repurchase Amount	$ 129	$ 100	$ 400	$ 629

The amount authorized by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration