Computation of Basic/Diluted Earnings Per Common Share (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Numerator:
Consolidated net income (loss)	$ 56,000,000	$ 226,000,000	$ 837,000,000	$ 795,000,000
Less: Distributed earnings to unvested share-based awards that participate in earnings	0	0	(4,000,000)	(4,000,000)
Less: Undistributed earnings allocated to unvested share-based awards that participate in earnings	(1,000,000)	(5,000,000)	(14,000,000)	(12,000,000)
Numerator for basic earnings per common share-income (loss) available to common shareholders	$ 55,000,000	$ 221,000,000	$ 819,000,000	$ 779,000,000
Denominator:
Denominator for basic earnings per common share - weighted-average common shares outstanding (in shares)	1,122	1,109	1,118	1,113
Effect of potential dilutive common shares under the treasury stock method:
Employee stock options (in shares)	12	5	9	5
Denominator for diluted earnings per common share - weighted-average common shares outstanding plus dilutive effect of employee stock options (in shares)	1,134	1,114	1,127	1,118
Basic earnings per common share (in dollars per share)	$ 0.05	$ 0.20	$ 0.73	$ 0.70
Diluted earnings per common share (in dollars per share)	$ 0.05	$ 0.20	$ 0.73	$ 0.70
Common stock weighted-average shares, unvested restricted stock rights (in shares)	24	27	25	23
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	2	24	8	20