Summary of Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Basic earnings per share - continuing operations:
Income from continuing operations attributable to common shareholders, net of tax	$ 74	$ 177	$ 168	$ 379
Participating securities dividends	0	0	0	0
Income from continuing operations available to common shareholders	74	177	168	379
Weighted average common shares outstanding (in shares)	326,000,000	326,000,000	326,000,000	326,000,000
Basic earnings per share - continuing operations (in dollars per share)	$ 0.23	$ 0.54	$ 0.51	$ 1.16
Diluted earnings per share - continuing operations:
Income from continuing operations available to common shareholders	74	177	168	379
Income impact of assumed conversions	0	1	0	1
Income from continuing operations available to common shareholders and assumed conversions	$ 74	$ 178	$ 168	$ 380
Weighted average common shares outstanding (in shares)	326,000,000	326,000,000	326,000,000	326,000,000
Incremental shares from assumed conversions (in shares)	8,000,000	3,000,000	7,000,000	2,000,000
Adjusted weighted average shares - diluted (in shares)	334,000,000	329,000,000	333,000,000	328,000,000
Diluted earnings per share - continuing operations (in dollars per share)	$ 0.22	$ 0.54	$ 0.50	$ 1.16
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)	3,266,857	5,896,940	4,928,510	5,896,940