Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt and Equity Securities, FV-NI [Line Items]
Investments	$ 251	$ 268
Investments in equity affiliates
Debt and Equity Securities, FV-NI [Line Items]
Investments	132	135
Marketable equity securities - Trading (See Note 10) | Trading Securities
Debt and Equity Securities, FV-NI [Line Items]
Investments	69	79
Other
Debt and Equity Securities, FV-NI [Line Items]
Investments	$ 50	$ 54