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Long-Term Debt Revolving Credit Facility (Details) $ in Thousands | 9 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2018 USD ($) | Oct. 24, 2018 USD ($) | Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items] |  |  |  |
Credit facility balance |  | $ 0 |  | $ 0
Line of Credit [Member] | Borrowing Base Utilization Of Less Than 25 Percent [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |  | 0.375% |  |
Line of Credit [Member] | Borrowing Base Utilization Of Less Than 25 Percent [Member] | Eurodollar [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 1.50% |  |
Line of Credit [Member] | Borrowing Base Utilization Of Less Than 25 Percent [Member] | Prime Rate [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 0.50% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 25 Percent Or More But Less Than 50 Percent [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |  | 0.375% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 25 Percent Or More But Less Than 50 Percent [Member] | Eurodollar [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 1.75% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 25 Percent Or More But Less Than 50 Percent [Member] | Prime Rate [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 0.75% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 50 Percent Or More But Less Than 75 Percent [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |  | 0.50% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 50 Percent Or More But Less Than 75 Percent [Member] | Eurodollar [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 2.00% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 50 Percent Or More But Less Than 75 Percent [Member] | Prime Rate [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 1.00% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 75 Percent Or More But Less Than 90 Percent [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |  | 0.50% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 75 Percent Or More But Less Than 90 Percent [Member] | Eurodollar [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 2.25% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 75 Percent Or More But Less Than 90 Percent [Member] | Prime Rate [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 1.25% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 90 Percent Or More [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage |  | 0.50% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 90 Percent Or More [Member] | Eurodollar [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 2.50% |  |
Line of Credit [Member] | Borrowing Base Utilization Of 90 Percent Or More [Member] | Prime Rate [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 1.50% |  |
Line of Credit [Member] | Revolving Credit Facility [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Line of credit agreement, maximum loan amount |  | $ 2,500,000 |  |
Line of credit facility, current borrowing base |  | 1,500,000 |  |
Line of credit agreement, aggregate lender commitments |  | 1,000,000 |  | 925,000
Credit facility balance | [1] | 0 |  | 0
Letters of credit | [2] | 200 |  | 200
Available borrowing capacity |  | 999,800 |  | 924,800
Unamortized deferred financing costs |  | $ 6,700 |  | $ 3,100
Line of Credit [Member] | Revolving Credit Facility [Member] | Subsequent Event [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Line of credit agreement, aggregate lender commitments |  |  | $ 1,000,000 |
Credit facility balance |  |  | 0 |
Letters of credit | [2] |  | 200 |
Available borrowing capacity |  |  | $ 999,800 |
Line of Credit [Member] | Revolving Credit Facility [Member] | Maximum [Member] | 12/31/18 QE through 12/31/19 QE [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Covenant Compliance, Total Funded Debt To Adjusted EBITDAX Ratio |  | 4.25 |  |
Line of Credit [Member] | Revolving Credit Facility [Member] | Maximum [Member] | 3/31/20 QE and Thereafter [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Covenant Compliance, Total Funded Debt To Adjusted EBITDAX Ratio |  | 4.00 |  |
Line of Credit [Member] | Revolving Credit Facility [Member] | Minimum [Member] |  |  |  |
Line of Credit Facility [Line Items] |  |  |  |
Debt Instrument, Covenant Compliance, Adjusted Current Ratio |  | 1.0 |  |
[1] | (1) Unamortized deferred financing costs attributable to the credit facility are presented as a component of other noncurrent assets on the accompanying balance sheets and totaled $6.7 million and $3.1 million as of September 30, 2018, and December 31, 2017, respectively. These costs are being amortized over the term of the credit facility on a straight-line basis.
[2] | (2) Letters of credit outstanding reduce the amount available under the credit facility on a dollar-for-dollar basis.

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- Definition Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The carrying value as of the balance sheet date of the noncurrent portion 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://fasb.org/us-gaap/role/ref/legacyRef -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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1336-112600 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1314-112600 + Details
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