4. Impairments

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.

Impairments during the six months ended June 30, 2015, were primarily related to the Company’s Greater Natural Buttes oil and gas and midstream properties in the Rockies, which were impaired due to lower commodity prices. Impairments of proved properties are included in impairment expense in the Company’s Consolidated Statements of Income. During the second quarter of 2014, the Company impaired a Gulf of Mexico property due to a reduction in estimated future cash flows.

In addition to the proved property impairments above, the Company also recognized a $935 million impairment of unproved Greater Natural Buttes properties during the six months ended June 30, 2015, as a result of lower commodity prices. Impairments of unproved properties are included in exploration expense in the Company’s Consolidated Statements of Income.