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, 2013		Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Basic earnings per share - continuing operations:
Income from continuing operations available to common shareholders	$ (106)		$ 183	$ 152	$ 360
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)	$ (0.33)		$ 0.56	$ 0.47	$ 1.10
Diluted earnings per share - continuing operations:
Income from continuing operations available to common shareholders	(106)		183	152	360
Income impact of assumed conversions	0		0	0	0
Income from continuing operations available to common shareholders and assumed conversions	$ (106)		$ 183	$ 152	$ 360
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)	0	[1]	8,000,000	3,000,000	7,000,000
Adjusted weighted average shares - diluted (in shares)	326,000,000		334,000,000	329,000,000	333,000,000
Diluted earnings per share – continuing operations (in dollars per share)	$ (0.33)		$ 0.55	$ 0.47	$ 1.08
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)			3,266,857	1,587,370	4,928,510

[1] Due to a loss for the three months ended June 30, 2013, there were no incremental shares in the computation because such shares would be considered antidilutive.