Investments (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments	$ 179	$ 367
Investments in equity affiliates
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments	46	221
Other
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments	55	69
Trading Securities [Member] | Marketable equity securities - Trading (See Note 9)
Schedule of Trading Securities and Other Trading Assets [Line Items]
Investments	$ 78	$ 77