Stockholders' Equity (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Disclosure of Repurchase Agreements [Abstract]
Investment Repurchase Agreement, Date of Agreement				Apr. 23, 2008
Stock Repurchase Program, Authorized Amount				$ 500
Payments for Repurchase of Common Stock	0
Stock Repurchase Program, Remaining Authorized Repurchase Amount	350
Noncontrolling Interest [Abstract]
PurchaseOfNoncontrollingInterestPercentage			1.80%
Payments to Acquire Additional Interest in Subsidiaries		$ 12
Noncontrolling Interest, Ownership Percentage by Parent	95.60%