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Fair Value Measurements Net Profits Plan (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2016 | Sep. 30, 2015 | Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast |  | 5 years |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net Profits Plan Liability Noncurrent |  | $ 7,611 |  |
Net Profits Plan Liability Noncurrent |  | $ 1,162 |  | $ 7,611
Net Profit Plan liability [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Fair Value Inputs, Discount Rate |  | 10.00% |  | 10.00%
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast |  | 5 years |  |
Period Used for Price Assumptions of Strip Prices for Liabilities |  | 1 year |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |  |  |
Net Profits Plan Liability Noncurrent |  | $ 7,611 |  |
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Period Increase (Decrease) | [1] | 20,389 |  |
Net settlements (1) (2) | [1],[2] | (26,838) |  |
Transfers in (out) of Level 3 |  | 0 |  |
Net Profits Plan Liability Noncurrent |  | 1,162 |  | $ 7,611
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 Divested Property |  | $ 21,600 | $ 3,800 |
[1] | Net changes in the Company’s Net Profits Plan liability are shown in the Change in Net Profits Plan liability line item in 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 $21.6 million for the nine months ended September 30, 2016, as a result of the divestitures of properties subject to the Net Profits Plan.

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- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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