Income Taxes - Components of Our Net Deferred Tax Assets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
State	$ 18	$ 19
Foreign	364	114
Tax credits	159	118
Postretirement benefits other than pensions	21	37
Pensions	158	24
Payroll and other accruals	24	18
Book over tax depreciation	68	(45)
Other accruals	163	80
Valuation allowance	(514)	(163)
Total deferred tax assets	461	202
Amortization of intangibles	82	0
Total deferred tax liabilities	82	0
Net deferred tax assets	$ 379	$ 202