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Derivatives - Classification of Gross Fair Values of Derivative Instruments, Excluding Cash Collateral (Detail) - Commodity derivatives - USD ($)
$ in Millions
Mar. 31, 2017
Dec. 31, 2016
Other current assets    
Derivatives, Fair Value [Line Items]    
Asset $ 392 $ 688
Liability 416 712
Other current liabilities(a)    
Derivatives, Fair Value [Line Items]    
Asset 0 0
Liability [1] 8 13
Deferred credits and other liabilities    
Derivatives, Fair Value [Line Items]    
Asset 0 0
Liability [1] $ 38 $ 47
[1] Includes embedded derivatives.