Income Taxes (Income Taxes And Related Effective Tax Rates) (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disclosure Income Taxes Income Taxes And Related Effective Tax Rates [Abstract]
Income (loss) before income taxes	$ (45)	$ (273)	$ (287)	$ (603)
Provision (benefit) for income taxes	$ 0	$ (6)	$ 2	$ 965
Effective tax rate	0.00%	2.20%	(0.70%)	(160.00%)

Disclosure - Income Taxes (Income Taxes And Related Effective Tax Rates) [Abstract]

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income tax contingencies. Includes, but not limited to, domestic tax contingency, foreign tax contingency, state and local tax contingency, and other contingencies.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

+ References

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

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-Publisher FASB
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