Summary of Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Basic earnings per share - continuing operations:
Income from continuing operations attributable to common shareholders, net of tax	$ 94	$ 202
Participating securities dividends	0	0
Income from continuing operations available to common shareholders	94	202
Weighted average common shares outstanding (in shares)	326,000,000	326,000,000
Basic earnings per share - continuing operations (in dollars per share)	$ 0.28	$ 0.62
Diluted earnings per share - continuing operations:
Income from continuing operations available to common shareholders	94	202
Income impact of assumed conversions	0	1
Income from continuing operations available to common shareholders and assumed conversions	$ 94	$ 203
Weighted average common shares outstanding (in shares)	326,000,000	326,000,000
Incremental shares from assumed conversions (in shares)	3,000,000	2,000,000
Adjusted weighted average shares - diluted (in shares)	329,000,000	328,000,000
Diluted earnings per share - continuing operations (in dollars per share)	$ 0.28	$ 0.62
Stock-Based Compensation Awards
Antidilutive Securities Excluded from Computation of Earnings Per Share
Stock-based compensation awards excluded from the computation of diluted earnings per share (in shares)	8,602,107	8,980,322

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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