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Summary of Significant Accounting Policies Other (Details) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Jan. 01, 2017 USD ($)
Basis of Presentation and Significant Accounting Policies [Line Items] |  |  |  |  |
Retained earnings |  | $ (665,657,000) | $ (794,020,000) |  |
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent |  | 65,890,000 | 210,455,000 |  |
Cash and cash equivalents |  | 313,943,000 | 9,372,000 | $ 18,000 |
Restricted Cash | [1] | 0 | 3,000,000 | 0 |
Cash, cash equivalents, and restricted cash at end of period | [2] | $ 313,943,000 | 12,372,000 | $ 18,000 |
Accounts Receivable Additional Disclosures [Abstract] |  |  |  |  |
Receivables Collection Period |  | 2 months |  |  |
Concentration of Credit Risk and Major Customers [Abstract] |  |  |  |  |
Number of individual entities within groups of entities under common ownership that represent more than 10 percent of total production revenue |  | 0 |  |  |
Number of Derivative Counterparties |  | 10 |  |  |
ASU 2016-09 Cumulative Effect Adjustment for Timing of Recognition of Excess Tax Benefits [Member] |  |  |  |  |
Basis of Presentation and Significant Accounting Policies [Line Items] |  |  |  |  |
Retained earnings |  |  |  |  | $ (44,300,000)
ASU 2016-09 Cumulative Effect of Actual Forfeiture Rate [Member] |  |  |  |  |
Basis of Presentation and Significant Accounting Policies [Line Items] |  |  |  |  |
Retained earnings |  |  |  |  | 700,000
Additional Paid in Capital |  |  |  |  | 1,100,000
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent |  |  |  |  | $ (400,000)
Revolving Credit Facility [Member] | Line of Credit [Member] |  |  |  |  |
Basis of Presentation and Significant Accounting Policies [Line Items] |  |  |  |  |
Long-term Line of Credit |  | $ 0 |  |  |
1.50% Senior Convertible Notes Due 2021 [Member] |  |  |  |  |
Basis of Presentation and Significant Accounting Policies [Line Items] |  |  |  |  |
Senior Notes, face amount |  | $ 172,500,000 | $ 172,500,000 |  |
Minimum [Member] |  |  |  |  |
Revenues [Abstract] |  |  |  |  |
Revenue Receipt, Days After Sale |  | 30 days |  |  |
Maximum [Member] |  |  |  |  |
Revenues [Abstract] |  |  |  |  |
Revenue Receipt, Days After Sale |  | 90 days |  |  |
Oil and Gas Properties [Member] |  |  |  |  |
Impairment of Proved, Unproved, and Other Properties [Abstract] |  |  |  |  |
Period of New York Mercantile Exchange Strip Pricing Used for Price Forecast |  | 5 years |  |  |
Property, Plant and Equipment, Other Types [Member] | Minimum [Member] |  |  |  |  |
Property, Plant and Equipment [Abstract] |  |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives |  | 3 years |  |  |
Property, Plant and Equipment, Other Types [Member] | Maximum [Member] |  |  |  |  |
Property, Plant and Equipment [Abstract] |  |  |  |  |
Property, Plant and Equipment, Estimated Useful Lives |  | 30 years |  |  |
Asset Retirement Obligation Costs [Member] | Minimum [Member] |  |  |  |  |
Asset Retirement Obligations [Abstract] |  |  |  |  |
Fair Value Assumptions, Risk Free Interest Rate |  | 5.50% |  |  |
Asset Retirement Obligation Costs [Member] | Maximum [Member] |  |  |  |  |
Asset Retirement Obligations [Abstract] |  |  |  |  |
Fair Value Assumptions, Risk Free Interest Rate |  | 12.00% |  |  |
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Major Customer One [Member] |  |  |  |  |
Concentration of Credit Risk and Major Customers [Abstract] |  |  |  |  |
Entity-Wide Revenue, Major Customer, Percentage | [3] | 10.00% | 5.00% | 4.00% |
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Major Customer Two [Member] |  |  |  |  |
Concentration of Credit Risk and Major Customers [Abstract] |  |  |  |  |
Entity-Wide Revenue, Major Customer, Percentage | [4] | 7.00% | 18.00% | 21.00% |
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Unnamed Major Customer One with Related Entities [Member] |  |  |  |  |
Concentration of Credit Risk and Major Customers [Abstract] |  |  |  |  |
Entity-Wide Revenue, Major Customer, Percentage | [5] | 17.00% | 15.00% | 10.00% |
Customer Concentration Risk [Member] | Oil, gas, and NGLS revenue [Member] | Unnamed Major Customer Two with Related Entities [Member] |  |  |  |  |
Concentration of Credit Risk and Major Customers [Abstract] |  |  |  |  |
Entity-Wide Revenue, Major Customer, Percentage | [5] | 8.00% | 8.00% | 11.00% |
[1] | Restricted cash is included in other noncurrent assets on the accompanying balance sheets.
[2] | (1) Refer to Note 1 – Summary of Significant Accounting Policies for a reconciliation of cash, cash equivalents, and restricted cash reported to the amounts reported within the accompanying balance sheets.
[3] | This major customer is a purchaser of the Company’s production from its Permian region.
[4] | This major customer was the operator of the Company’s outside-operated Eagle Ford shale program, which was divested of during the first quarter of 2017. Prior to the divestiture, the Company was party to various marketing agreements, which included certain gathering, transportation, and processing throughput commitments. Because the Company shared with the operator the risk of non-performance by its counterparty purchasers, the Company included the operator as a major customer in the table above. Several of the operator’s counterparty purchasers under these contracts were also direct purchasers of the Company’s production from other areas.
[5] | In the aggregate these groups of entities under common ownership represent more than 10 percent of total oil, gas, and NGL production revenue for the period(s) shown, however, none of the individual entities comprising either group represented more than 10 percent of the Company’s total oil, gas, and NGL production revenue.

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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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