Summary of Significant Accounting Policies (Earnings Per Share) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Basic earnings per share - continuing operations:
Income from continuing operations available to common shareholders									$ 879	$ 1,503	$ 1,041
Weighted average common shares outstanding (in shares)									326,000,000	326,000,000	326,000,000
Basic earnings (loss) per share – continuing operations (in dollars per share)	$ 0.81	$ 1.42	$ (0.33)	$ 0.79	$ 2.42	$ 1.09	$ 0.56	$ 0.54	$ 2.70	$ 4.61	$ 3.20
Diluted earnings per share - continuing operations:
Income from continuing operations available to common shareholders									879	1,503	1,041
Income impact of assumed conversions									1	(1)	(1)
Income from continuing operations available to common shareholders and assumed conversions									$ 880	$ 1,502	$ 1,040
Weighted average common shares outstanding (in shares)									326,000,000	326,000,000	326,000,000
Incremental shares from assumed conversions (in shares)									3,000,000	4,000,000	3,000,000
Adjusted weighted average shares - diluted (in shares)									329,000,000	330,000,000	329,000,000
Diluted earnings (loss) per share – continuing operations (in dollars per share)	$ 0.81	$ 1.41	$ (0.33)	$ 0.78	$ 2.39	$ 1.09	$ 0.55	$ 0.54	$ 2.67	$ 4.55	$ 3.17
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)					7,492,552				3,977,894		5,847,094