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Fair Value Measurements Net Profits Plan (Details) | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2015 USD ($) A | Jun. 30, 2014 USD ($) | Jun. 30, 2015 USD ($) A | Jun. 30, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Net Profits Plan liability |  |  |  | $ 27,136,000 |
Net Profits Plan liability |  | $ 18,326,000 |  | $ 18,326,000 |
Number of Periods Used for Price Assumptions of Strip Prices of Liabilities | A |  | 5 |  | 5 |
Net Profit Plan liability [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Net Profits Plan liability |  |  |  | $ 27,136,000 |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) | [1] |  |  | (1,796,000) |
Net settlements (1) (2) | [1],[2] |  |  | (7,014,000) |
Transfers in (out) of Level 3 |  |  |  | 0 |
Net Profits Plan liability |  | $ 18,326,000 |  | $ 18,326,000 |
Discount Rate Used to Calculate Currently in Payout Liabilities |  | 12.00% |  | 12.00% |
Number of Periods Used for Price Assumptions of Strip Prices of Liabilities |  | 5 |  | 5 |
Period Used for Price Assumptions of Strip Prices for Liabilities |  | 1 |  | 1 |
Percent Change in Commodity Prices for Sensitivity Analysis |  | 5.00% |  | 5.00% |
Sensitivity Analysis Change in Liability, Due to Change in Commodity Prices |  | $ 1,794,000 |  | $ 1,794,000 |
Percent Increase and Decrease in Discount Rate for Sensitivity Analysis |  | 1.00% |  | 1.00% |
Sensitivity Analysis Change in Liability Due to Change in Discount Rate |  | $ 650,000 |  | $ 650,000 |
Net Profits Plan [Member] |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |
Cash Payments Made or Accrued under Profit Sharing Plan Related to Divestiture Proceeds |  | $ 3,800,000 | $ 8,500,000 | $ 3,800,000 | $ 8,500,000
[1] | Net changes in the Company’s Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item of the accompanying statements of operations.
[2] | Settlements represent cash payments made or accrued under the Net Profits Plan. The amount in the table includes cash payments made or accrued under the Net Profits Plan of $3.8 million for the six-month period ended June 30, 2015, as a result of the divestitures of properties subject to the Net Profits Plan

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