EPS (Calculation of Earnings Per Share and the Reconciliation of Earnings Per Share to Earnings Per Diluted Share) (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Earnings per share:
Net income (loss) available to common shareholders	$ 689	$ 290
Less: Income allocated to participating securities	8	4
Earnings per share - basic	681	286
Earnings per diluted share:
Net income available to common shareholders	689	290
Stock-based awards	0	0
Net income available to common shareholders plus assumed conversions	689	290
Less: Income allocated to participating securities	8	4
Net income allocated to common shareholders	$ 681	$ 286
Earnings per share:
Net income allocated to common shareholders	689,820,295	747,667,521
Effect of dilutive securities:
Stock-based awards	14,000,000	13,000,000
Net income allocated to common shareholders	704,100,936	760,809,239
Earnings per share:
Earnings per share - basic	$ 0.99	$ 0.38
Earnings per diluted share:
Earnings per share - diluted	$ 0.97	$ 0.38

Net Income (Loss) Allocated to Common Stockholders, Basic

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Net Income (Loss) Allocated to Common Stockholders, Diluted

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Adjustment amount for dilutive impact to reconcile net income available to common shareholders as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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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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Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of share based payment arrangements using the treasury stock method.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities, and addition from assumption of issuance of common shares for dilutive potential common shares; of income (loss) available to common shareholders.

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Amount of undistributed earnings (loss) allocated to participating securities for the basic earnings (loss) per share or per unit calculation under the two-class method.

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Amount of undistributed earnings (loss) allocated to participating securities for the diluted earnings (loss) per share or per unit calculation under the two-class method.

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The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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