Impairments (Tables)

12 Months Ended

Dec. 31, 2012

Goodwill and Intangible Assets Disclosure [Abstract]

Details of Impairment of Long-Lived Assets Held and Used by Asset

The following table summarizes impairment charges recorded during the periods presented:



	Year Ended December 31,
	2012		2011		2010
Oil and gas properties	$	103,417	$	104,688	$	43,067
Other - tubular inventory and well materials	1,067		—		2,892
	$	104,484	$	104,688	$	45,959

Fair Value Measurements, Nonrecurring

The following table summarizes the aggregate fair values of the assets described below, by asset category and the classification of inputs within the fair value measurement hierarchy, at the respective dates of impairment:



	Fair Value
	Measurement		Level 1		Level 2		Level 3
Year ended December 31, 2012:
Long-lived assets held for use	$	14,801	$	—	$	—	$	14,801
Long-lived assets sold during the year	96,099		—		—		96,099

Year ended December 31, 2011:
Long-lived assets held for use	$	26,625	$	—	$	—	$	26,625
Long-lived assets sold during the year	30,342		—		—		30,342

- Definition

Tabular disclosure for impairment of long-lived assets held and used by an entity which includes a description of the impaired long-lived asset and facts and circumstances leading to the impairment, aggregate amount of the impairment loss and where the loss is located in the income statement, method(s) for determining fair value, and the segment in which the impaired long-lived asset is reported.

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- Definition

Tabular disclosure of assets and liabilities by class, including financial instruments measured at fair value that are classified in shareholders' equity, if any, that are measured at fair value on a nonrecurring basis in periods after initial recognition (for example, impaired assets). Disclosures may include, but are not limited to: (a) the fair value measurements recorded and the reasons for the measurements and (b) the level within the fair value hierarchy in which the fair value measurements are categorized in their entirety (levels 1, 2, 3).

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