Impairments (Tables)

12 Months Ended

Dec. 31, 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 at December 31:

	2015				2014				2013
millions	Impairment		Fair Value(1)		Impairment		Fair Value(1)		Impairment		Fair Value(1)
Oil and gas exploration and production
Long-lived assets held for use
U.S. onshore properties	$	3,684	$	1,253	$	545	$	552	$	142	$	271
Gulf of Mexico properties	349		65		276		223		562		242
Cost-method investment (2)	3		32		3		32		11		32
Midstream
Long-lived assets held for use	1,039		212		12		—		79		36
Total impairments	$	5,075	$	1,562	$	836	$	807	$	794	$	581

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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.