Impairments - Impairments and Fair Values by Segment Table (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Impaired Long Lived Assets Held and Used [Line Items]
Total impairments		$ 0	$ 27	$ 383	$ 61
Assets Impaired During Fiscal Year to Date [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Total impairments				383
Assets Impaired During Fiscal Year to Date [Member] | Exploration and Production [Member] | U.S. Onshore Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use				2
Assets Impaired During Fiscal Year to Date [Member] | Exploration and Production [Member] | Gulf of Mexico Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use				211
Assets Impaired During Fiscal Year to Date [Member] | Midstream [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use				169
Assets Impaired During Fiscal Year to Date [Member] | Other [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use				1
Assets Impaired During Fiscal Year to Date [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Total fair value	[1]	292		292
Assets Impaired During Fiscal Year to Date [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Income Approach Valuation Technique [Member] | Exploration and Production [Member] | U.S. Onshore Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	3		3
Assets Impaired During Fiscal Year to Date [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Income Approach Valuation Technique [Member] | Exploration and Production [Member] | Gulf of Mexico Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	231		231
Assets Impaired During Fiscal Year to Date [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Income Approach Valuation Technique [Member] | Midstream [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	[1]	58		58
Assets Impaired During Fiscal Year to Date [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member] | Income Approach Valuation Technique [Member] | Other [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. The primary assumptions used to estimate undiscounted future net cash flows include anticipated future production, commodity prices, and capital and operating costs.