Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Decrease in unrecognized tax benefits within the next twelve months	$ 175		$ 175
Increase in unrecognized tax benefits within the next twelve months	$ 25		$ 25
Effective tax rate	6.00%	15.10%	12.50%	18.20%
U.S. corporate income tax rate					21.00%

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

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

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

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Amount of increase reasonably possible in the next twelve months for the unrecognized tax benefit.

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