Earnings Per Share (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Numerator for earnings (loss) per share, basic
Income (loss) from continuing operations attributable to controlling interest	$ (481)	$ 464
Undistributed earnings allocable to participating securities		(4)
Income (loss) from continuing operations available to shareholders	(481)	460
Denominator for earnings (loss) per share, basic
Weighted-average shares outstanding	363	361
Weighted-average shares for per share calculation, basic	363	361
Per share earnings (loss) from continuing operations, basic	$ (1.32)	$ 1.27
Numerator for earnings (loss) per share, diluted
Income (loss) from continuing operations attributable to controlling interest	(481)	464
Undistributed earnings allocable to participating securities		(4)
Income (loss) from continuing operations available to shareholders	$ (481)	$ 460
Denominator for earnings (loss) per share, diluted
Weighted-average shares outstanding	363	361
Weighted-average shares for per share calculation, diluted	363	361
Per share earnings (loss) from continuing operations, diluted	$ (1.32)	$ 1.27
Share-based awards
Anti-dilutive securities
Share-based awards excluded from earnings per share calculation (in shares)	5.0	2.3

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Amount of income (loss) from continuing operations attributable to the parent. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

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The amount of net income (loss) from continuing operations per each share of common stock or unit outstanding during the reporting period.

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The amount of net income (loss) derived from continuing operations during the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period).

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Net Income or Loss Available to Common Stockholders plus adjustments resulting from the assumption that dilutive convertible securities were converted, options or warrants were exercised, or that other shares were issued upon the satisfaction of certain conditions.

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The aggregate value of preferred stock dividends and other adjustments necessary to derive net income apportioned to common stockholders.

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