Impairments (Tables)

9 Months Ended

Sep. 30, 2013

Table Text Block [Abstract]

Schedule of Impairment Expense

       The following summarizes impairments by segment:

	Three Months Ended   September 30,				Nine Months Ended   September 30,
millions	2013		2012		2013		2012
Oil and gas exploration and production
Long-lived assets held for use
U.S. onshore properties	$	—	$	2	$	—	$	81
Gulf of Mexico properties	593		—		593		67
Cost-method investment	—		1		10		12
Midstream
Long-lived assets held for use	—		1		29		6
Impairments	$	593	$	4	$	632	$	166

Nonrecurring Fair Value Measurements Table

       The following summarizes the post-impairment fair value of the above-described assets, by asset category and input level within the fair-value hierarchy:

millions
2013	Level 1		Level 2		Level 3 (1)		Total
Long-lived assets held for use	$	—	$	—	$	266	$	266
Cost-method investment (2)	—		—		32		32
2012
Long-lived assets held for use	$	—	$	—	$	38	$	38
Cost-method investment (2)	—		—		34		34

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⁽¹⁾  The income approach was used to measure fair value.

⁽²⁾  This represents the Company’s after-tax net investment.