Impairments (Tables)

6 Months Ended

Jun. 30, 2015

Asset Impairment Charges [Abstract]

Schedule of Impairment Expense

The following summarizes impairments of proved properties and the related post-impairment fair values by segment:

	Three Months Ended				Six Months Ended
millions	Impairment		Fair Value (1)		Impairment		Fair Value (1)
June 30, 2015
Oil and gas exploration and production
Long-lived assets held for use
U.S. onshore properties	$	4	$	12	$	2,303	$	1,303
Gulf of Mexico properties	17		—		25		—
Cost-method investment (2)	1		32		1		32
Midstream
Long-lived assets held for use	8		199		484		202
Total	$	30	$	243	$	2,813	$	1,537
June 30, 2014
Oil and gas exploration and production
Long-lived assets held for use
Gulf of Mexico properties	$	115	$	327	$	115	$	327
Cost-method investment (2)	1		32		2		32
Midstream
Long-lived assets held for use	1		—		3		—
Total	$	117	$	359	$	120	$	359

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⁽¹⁾  Measured as of the impairment date using the income approach and Level 3 inputs.

⁽²⁾  Represents the after-tax net investment.