Acquisitions, Divestitures, and Assets Held for Sale (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		1 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Apr. 30, 2015	Nov. 25, 2014
Property, Plant, and Equipment [Line Items]
Purchase price	$ 0	$ 4
(Gains) losses on divestitures, net	334	(1,459)
Proceeds from divestitures	22	3,257
Oil and Gas Exploration and Production Reporting Segment [Member] | Held-for-sale [Member]
Property, Plant, and Equipment [Line Items]
Current assets associated with assets held for sale	29
Long-term assets associated with assets held for sale	743
Current liabilities associated with assets held for sale	17
Long-term liabilities associated with assets held for sale	78
Oil and Gas Exploration and Production Reporting Segment [Member] | Held-for-sale [Member] | Certain U.S. Onshore Rockies Assets [Member] | Nonrecurring [Member] | Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 2 [Member]
Property, Plant, and Equipment [Line Items]
Loss on assets held for sale	340
Oil and Gas Exploration and Production Reporting Segment [Member] | Assets Disposed of by Sale [Member] | Certain U.S. Onshore Rockies Assets [Member] | Subsequent Event [Member]
Property, Plant, and Equipment [Line Items]
Proceeds from divestitures			703
Gathering and Processing Assets in the Delaware basin [Member]
Property, Plant, and Equipment [Line Items]
Purchase price				1,554
Changes to the fair value of assets acquired and liabilities assumed