Computation of Earnings (Loss) Per Basic/Diluted Common Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Numerator:
Consolidated net income (loss)	$ 394	$ 293
Less: Distributed earnings to unvested share-based awards that participate in earnings	(4)	(5)
Less: Undistributed earnings allocated to unvested share-based awards that participate in earnings	(3)	(3)
Numerator for basic earnings per common share-income (loss) available to common shareholders	$ 387	$ 285
Denominator:
Denominator for basic earnings per common share - weighted-average common shares outstanding (in shares)	723	709
Effect of potential dilutive common shares under the treasury stock method:
Employee stock options and others (in shares)	8	11
Denominator for diluted earnings per common share - weighted-average common shares outstanding plus dilutive common shares under treasury stock method (in shares)	731	720
Basic earnings per common share (in dollars per share)	$ 0.54	$ 0.40
Diluted earnings per common share (in dollars per share)	$ 0.53	$ 0.40
Performance shares not included in the computation of EPS	4	3
Common stock weighted-average shares, unvested restricted stock rights (in shares)	10	17
Options
Antidilutive [Line Items]
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	6	3