4. Impairments

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



	Three Months Ended
millions	Impairment		Fair Value⁽¹⁾
March 31, 2015
Oil and gas exploration and production
Long-lived assets held for use
U.S. onshore properties	$	2,307	$	1,299
Midstream
Long-lived assets held for use	476		206
Total	$	2,783	$	1,505

March 31, 2014
Oil and gas exploration and production
Cost-method investment ⁽²⁾	$	1	$	32
Midstream
Long-lived assets held for use	2		—
Total	$	3	$	32

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⁽¹⁾	Measured using the income approach and Level 3 inputs.


⁽²⁾	Represents the after-tax net investment.

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