Income Taxes - Composition of Net Deferred Tax Asset by Jurisdiction (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Line Items]
Deferred tax assets	$ 2,556	$ 3,112
Valuation allowance	(1,684)	$ (1,927)	$ (1,755)	$ (712)
Deferred tax liabilities	(571)
Total deferred tax asset	301
Domestic [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets	891
Valuation allowance	(779)
Deferred tax liabilities	(102)
Total deferred tax asset	10
Foreign [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets	1,665
Valuation allowance	(905)
Deferred tax liabilities	(469)
Total deferred tax asset	$ 291