Summary of Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended			9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Basic earnings per share - continuing operations:
Income from continuing operations available to common shareholders	$ 463		$ 357	$ 615	$ 717
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)	$ 1.42		$ 1.09	$ 1.88	$ 2.20
Diluted earnings per share - continuing operations:
Income from continuing operations available to common shareholders	463		357	615	717
Income impact of assumed conversions	0		0	1	0
Income from continuing operations available to common shareholders and assumed conversions	$ 463		$ 357	$ 616	$ 717
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)	2,000,000	[1]	3,000,000	3,000,000	2,000,000
Adjusted weighted average shares - diluted (in shares)	328,000,000		329,000,000	329,000,000	328,000,000
Diluted earnings per share – continuing operations (in dollars per share)	$ 1.41		$ 1.09	$ 1.87	$ 2.18
Stock-Based Compensation Awards
Diluted earnings per share - continuing operations:
Stock-based compensation awards excluded from the computation of diluted earnings per share (in shares)	4,109,363		3,238,581	4,109,363	4,819,683

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