Financial Risk Management Activities - Corporate Financial Risk Management Activities - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Derivative Instruments Gain Loss [Line Items]
Amount of total gains (losses) from Brent & WTI crude oil collars, which impact Sales and other operating revenues		$ (35,000,000)		$ (18,000,000)
Pre-tax gains (losses) associated with changes in time value of Brent and WTI crude oil collars		(35,000,000)		(23,000,000)
Crude Oil
Derivative Instruments Gain Loss [Line Items]
Outstanding gross notional amount, in USD	$ 0		$ 0
Interest Rate Swaps
Derivative Instruments Gain Loss [Line Items]
Outstanding gross notional amount, in USD	1,300,000,000		1,300,000,000		$ 1,300,000,000
Unrealized change in fair value of interest rate swaps - increase/(decrease)	4,000,000	(6,000,000)	18,000,000	4,000,000
Foreign Exchange
Derivative Instruments Gain Loss [Line Items]
Outstanding gross notional amount, in USD	859,000,000		859,000,000		967,000,000
Total foreign exchange gains and (losses) reported in Other, net in Revenues and Non-Operating Income in the Statement of Consolidated Income	15,000,000	(7,000,000)	21,000,000	8,000,000
Gain (Loss) on foreign exchange contracts not designated as hedging instruments	33,000,000	(41,000,000)	13,000,000	57,000,000
After tax foreign currency translation adjustments included in Accumulated other comprehensive income (loss)	(27,000,000)	$ 72,000,000	142,000,000	$ (48,000,000)
Accumulated cumulative currency translation adjustment	$ (959,000,000)		$ (959,000,000)		$ (1,101,000,000)