Financial Instruments - Schedule of Carrying Values and Fair Values of Financial Instruments (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Carrying Value
Derivative [Line Items]
Cash and cash equivalents	$ 1,205	$ 2,150
Restricted cash	3	4
Derivatives – current asset	37	61
Noncurrent receivables	20	20
Derivatives – noncurrent asset	19	33
Available-for-sale securities	96	106
Short-term debt	45	38
Derivatives – current liability	29	45
Derivatives – noncurrent liability	8	14
Long-term debt, less amount due within one year	6,309	6,806
Fair Value
Derivative [Line Items]
Cash and cash equivalents	1,205	2,150
Restricted cash	3	4
Derivatives – current asset	37	61
Noncurrent receivables	20	20
Derivatives – noncurrent asset	19	33
Available-for-sale securities	96	106
Short-term debt	45	38
Derivatives – current liability	29	45
Derivatives – noncurrent liability	8	14
Long-term debt, less amount due within one year	$ 6,631	$ 7,443