Impairments - Impairments and Fair Values by Segment Table (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Impaired Long Lived Assets Held and Used [Line Items]
Total impairments		$ 27	$ 758	$ 61	$ 3,571
Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Total fair value	[1]	654	2,239	654	2,239
Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Assets Impaired During 3rd Quarter [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Total fair value	[1]	32	767	32	767
Oil and Gas Exploration and Production Reporting Segment [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of cost-method investment		0	1	2	2
Oil and Gas Exploration and Production Reporting Segment [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of cost-method investment	[1],[2]	32	32	32	32
Oil and Gas Exploration and Production Reporting Segment [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Assets Impaired During 3rd Quarter [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of cost-method investment	[1],[2]	0	32	0	32
Oil and Gas Exploration and Production Reporting Segment [Member] | U.S. Onshore Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use		23	641	27	2,944
Oil and Gas Exploration and Production Reporting Segment [Member] | U.S. Onshore Properties [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	617	1,904	617	1,904
Oil and Gas Exploration and Production Reporting Segment [Member] | U.S. Onshore Properties [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Assets Impaired During 3rd Quarter [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	32	634	32	634
Oil and Gas Exploration and Production Reporting Segment [Member] | Gulf of Mexico Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use		0	101	2	126
Oil and Gas Exploration and Production Reporting Segment [Member] | Gulf of Mexico Properties [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	0	94	0	94
Oil and Gas Exploration and Production Reporting Segment [Member] | Gulf of Mexico Properties [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Assets Impaired During 3rd Quarter [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	0	94	0	94
Midstream Reporting Segment [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use		3	15	24	499
Midstream Reporting Segment [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	5	209	5	209
Midstream Reporting Segment [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Assets Impaired During 3rd Quarter [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	0	$ 7	0	$ 7
Other and Intersegment Eliminations [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use		1		6
Other and Intersegment Eliminations [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	0		0
Other and Intersegment Eliminations [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member] | Assets Impaired During 3rd Quarter [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	$ 0		$ 0

[1] Measured as of the impairment date using the income approach and Level 3 inputs.

[2] Represents the after-tax net investment.