Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income (numerator):
Net income (loss)	$ (667)	$ (992)	$ (1,291)	$ (1,472)
Weighted average shares (denominator):
Weighted-average shares — basic	198.0	163.0	188.0	154.0
Dilution effect of stock options and unvested restricted stock awards and restricted stock units outstanding at end of period(1)	0.0	0.0	0.0	0.0
Weighted-average shares — diluted	198.0	163.0	188.0	154.0
Basic --
Basic	$ (3.36)	$ (6.09)	$ (6.87)	$ (9.55)
Diluted --
Diluted	$ (3.36)	$ (6.09)	$ (6.87)	$ (9.55)
Earnings Per Share (Textuals) [Abstract]
Incremental shares attributable to the assumed exercise of outstanding stock options and the assumed vesting of unvested restricted stock and restricted stock units	1.6	1.5	1.3	1.4

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

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The amount of net income (loss) for 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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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

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