Impairment of Property and Equipment	12 Months Ended
Dec. 31, 2012
Property, Plant and Equipment Impairment or Disposal [Abstract]
Impairment of Property and Equipment	Impairment of Property and Equipment We impair our long-lived assets, including oil and gas properties and contract drilling equipment, when estimated undiscounted future net cash flows of an asset are less than its carrying value. The amount of any such impairment is recognized based on the difference between the carrying value and the estimated fair value of the asset. We categorize the measurement of fair value of these assets as Level 3 inputs. We estimate the fair value of the impaired property by applying weighting factors to fair values determined under three different methods: discounted cash flow method, flowing daily production method and proved reserves per BOE method. We then assign applicable weighting factors based on the relevant facts and circumstances. We recorded provisions for impairment of proved properties triggered by a combination of well performance and lower reserve estimates due to performance and changes in oil and gas prices aggregating $5.9 million in 2012, $10.4 million in 2011, and $11.9 million in 2010 to reduce the carrying value of those properties to their estimated fair values. The 2012 provision related to $5.4 million for certain non-core properties in the Permian Basin. The 2011 provision related to $10.4 million for certain non-core properties in the Permian Basin and other non-core areas. The 2010 provision related primarily to $11.1 million for certain non-core properties in the Permian Basin. Unproved properties are nonproducing and do not have estimable cash flow streams. Therefore, we estimate the fair value of individually significant prospects by obtaining, when available, information about recent market transactions in the vicinity of the prospects and adjust the market data as needed to give consideration to the proximity of the prospects to known fields and reservoirs, the extent of geological and geophysical data on the prospects, the remaining terms of leases holding the acreage in the prospects, recent drilling results in the vicinity of the prospects, and other risk-related factors such as drilling and completion costs, estimated product prices and other economic factors. Individually insignificant prospects are grouped and impaired based on remaining lease terms and our historical experience with similar prospects. Based on the assessments previously discussed, we will impair our unproved oil and gas properties when we determine that a prospect’s carrying value exceed its estimated fair value. We categorize the measurement of fair value of these assets as Level 3 inputs. We recorded provisions for impairment of unproved properties aggregating $1.4 million, $6.2 million and $7.8 million in 2012, 2011 and 2010, respectively, and charged these impairments to abandonments and impairments in the accompanying consolidated statements of operations and comprehensive income (loss).

Impairment of Property and Equipment

We impair our long-lived assets, including oil and gas properties and contract drilling equipment, when estimated undiscounted future net cash flows of an asset are less than its carrying value. The amount of any such impairment is recognized based on the difference between the carrying value and the estimated fair value of the asset. We categorize the measurement of fair value of these assets as Level 3 inputs. We estimate the fair value of the impaired property by applying weighting factors to fair values determined under three different methods: discounted cash flow method, flowing daily production method and proved reserves per BOE method. We then assign applicable weighting factors based on the relevant facts and circumstances. We recorded provisions for impairment of proved properties triggered by a combination of well performance and lower reserve estimates due to performance and changes in oil and gas prices aggregating $5.9 million in 2012, $10.4 million in 2011, and $11.9 million in 2010 to reduce the carrying value of those properties to their estimated fair values. The 2012 provision related to $5.4 million for certain non-core properties in the Permian Basin. The 2011 provision related to $10.4 million for certain non-core properties in the Permian Basin and other non-core areas. The 2010 provision related primarily to $11.1 million for certain non-core properties in the Permian Basin.

Unproved properties are nonproducing and do not have estimable cash flow streams. Therefore, we estimate the fair value of individually significant prospects by obtaining, when available, information about recent market transactions in the vicinity of the prospects and adjust the market data as needed to give consideration to the proximity of the prospects to known fields and reservoirs, the extent of geological and geophysical data on the prospects, the remaining terms of leases holding the acreage in the prospects, recent drilling results in the vicinity of the prospects, and other risk-related factors such as drilling and completion costs, estimated product prices and other economic factors. Individually insignificant prospects are grouped and impaired based on remaining lease terms and our historical experience with similar prospects. Based on the assessments previously discussed, we will impair our unproved oil and gas properties when we determine that a prospect’s carrying value exceed its estimated fair value. We categorize the measurement of fair value of these assets as Level 3 inputs. We recorded provisions for impairment of unproved properties aggregating $1.4 million, $6.2 million and $7.8 million in 2012, 2011 and 2010, respectively, and charged these impairments to abandonments and impairments in the accompanying consolidated statements of operations and comprehensive income (loss).