Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Schedule Of Income Tax [Line Items]
Effective tax rates	6.10%	(0.10%)	9.30%	1.00%
U.S. federal corporate tax rate			21.00%		35.00%
Tax cuts and jobs act of 2017, Adjustments of provisional income tax expense			$ 9
Charge relating to change in U.S. federal corporate tax rate			69
Change in valuation allowance			(69)
Charge relating to one-time transition tax on unremitted foreign earnings			33
Net operating loss deferred tax asset, additional charge			9
Maximum [Member]
Schedule Of Income Tax [Line Items]
Global intangible low taxed income provisions and recognized provisional tax expense			1
Valuation Allowance,Net Operating Loss [Member]
Schedule Of Income Tax [Line Items]
Change in valuation allowance			$ (9)