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Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal statutory income tax rate			21.00%		35.00%
Income tax benefit related to revaluation of net deferred tax liability					$ 242,000,000
Additional tax expense related to provisional estimate of one-time transition tax			$ 0
Provision (benefit) for income taxes	$ 29,000,000	$ (13,000,000)	37,000,000	$ (43,000,000)
Unrecognized tax benefit	$ 92,000,000		$ 92,000,000

X

- Definition

Amount of reasonable estimate for income tax expense (benefit) for remeasurement of deferred tax from change in tax rate pursuant to Tax Cuts and Jobs Act for which accounting for tax effect is incomplete.

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Amount of reasonable estimate for income tax expense from transition tax on accumulated earnings of controlled foreign corporation deemed repatriated pursuant to Tax Cuts and Jobs Act for which accounting for tax effect is incomplete.

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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

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Amount of unrecognized tax benefits.

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