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Long-Term Debt (Narrative) (Details) |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |  |  |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
May 04, 2017 USD ($) bank | Dec. 21, 2016 USD ($) | Dec. 13, 2016 USD ($) | Dec. 12, 2016 | Oct. 14, 2016 USD ($) | Jan. 31, 2016 | Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($) | May 05, 2017 USD ($) | Mar. 29, 2017 USD ($) | Dec. 31, 2016 USD ($) | Oct. 31, 2016 USD ($) | Jun. 04, 2015 USD ($) | Apr. 21, 2015 USD ($) | Aug. 18, 2014 USD ($) | Dec. 21, 2012 USD ($) | Oct. 17, 2012 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capitalized interest expense, undeveloped properties |  |  |  |  |  |  | $ 2,100,000 | $ 4,700,000 | $ 8,800,000 | $ 7,700,000 |  |  |  |  |  |  |  |  |
Capitalized interest expense, building construction |  |  |  |  |  |  |  |  | 8,753,000 | 8,920,000 |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | 30,111,000 |  | 30,111,000 |  |  |  | $ 27,174,000 |  |  |  |  |  |
Construction loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capitalized interest expense, building construction |  |  |  |  |  |  | 0 | $ 500,000 | 0 | $ 1,200,000 |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | $ 100,000 |  | $ 100,000 |  |  |  |  |  |  |  |  |  |
Amended and restated credit agreement | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt covenant ratio for future EBITDAX |  |  |  |  |  |  | 4.00 |  | 4.00 |  |  |  |  |  |  |  |  |  |
Amended and restated credit agreement | Revolving credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt covenant ratio for EBITDAX |  |  |  |  |  |  | 3.00 |  | 3.00 |  |  |  |  |  |  |  |  |  |
7.75% Senior Notes due 2020 | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 0 |  | $ 0 |  |  |  | 0 |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 7.75% |  | 7.75% |  |  |  |  |  |  |  |  |  |
Debt instrument, amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 600,000,000.0 |  |
Debt instrument, amount repurchased |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 600,000,000.0 |  |  |  |  |
6.000% Senior Notes due 2024 | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 650,000,000 |  | $ 650,000,000 |  |  |  | 650,000,000 |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  | 6.00% |  | 6.00% |  | 6.00% |  |  |  |  | 6.00% |  |  |  |  |
Debt instrument, amount |  |  |  |  | $ 650,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of Senior Notes |  |  |  |  | $ 638,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | $ 10,200,000 |  | $ 10,200,000 |  |  |  |  |  |  |  |  |  |
6.625% Senior Notes due 2023 | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 350,000,000 |  | $ 350,000,000 |  |  |  | 350,000,000 |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 6.625% |  | 6.625% |  |  |  |  |  |  | 6.625% |  |  |
Debt instrument, amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 350,000,000.0 |  |  |
Long term debt, net of initial purchaser discounts and commissions and estimated offering expenses |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 343,600,000 |  |  |
Debt issuance costs, net |  |  |  |  |  |  | $ 5,500,000 |  | $ 5,500,000 |  |  |  |  |  |  |  |  |  |
6.375% Senior Notes due 2025 | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 600,000,000 |  | $ 600,000,000 |  |  |  | 600,000,000 |  |  |  |  |  |
Stated interest rate, percent |  | 6.375% |  |  |  |  | 6.375% |  | 6.375% |  |  |  |  |  |  |  |  |  |
Debt instrument, amount |  | $ 600,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of Senior Notes |  | $ 584,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | $ 14,300,000 |  | $ 14,300,000 |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Credit facility interest rate at the eurodollar rate |  |  |  |  |  |  |  |  | 3.74% |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Base rate | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 1.00% |  | 1.00% |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Base rate | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 2.00% |  | 2.00% |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Federal funds rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread, percent |  |  |  |  |  |  |  |  | 0.50% |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Eurodollar |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread, percent |  |  |  |  |  |  |  |  | 1.00% |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Eurodollar | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 2.00% |  | 2.00% |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Eurodollar | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 3.00% |  | 3.00% |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Amended and restated credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  | $ 1,500,000,000.0 |  | $ 1,500,000,000.0 |  |  |  |  |  |  |  |  |  |
Required minimum down payment, percent |  |  | 85.00% | 80.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum acquisition payment limit |  |  |  |  |  |  |  |  |  |  |  | $ 50,000,000 |  |  |  |  |  |  |
Minimum disposition of property limit |  |  |  |  |  |  |  |  |  |  |  | $ 50,000,000 |  |  |  |  |  |  |
Borrowing base | $ 700,000,000 |  |  |  |  |  | 1,000,000,000 |  | 1,000,000,000 |  |  |  |  |  |  |  |  |  |
Number of banks added to syndicate | bank | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | 365,000,000 |  | 365,000,000 |  |  |  | 0 |  |  |  |  |  |
Remaining borrowing capacity |  |  |  |  |  |  | 397,500,000 |  | 397,500,000 |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Unsecured debt | Amended and restated credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  | $ 1,600,000,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread, percent |  |  | 0.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Letter of credit | Amended and restated credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  | 1,200,000,000.0 |  | $ 1,200,000,000.0 |  | $ 1,000,000.0 |  |  |  |  |  |  |  |
Basis spread, percent |  |  |  |  |  |  |  |  | 0.50% |  |  |  |  |  |  |  |  |  |
Credit facility outstanding |  |  |  |  |  |  | 237,500,000 |  | $ 237,500,000 |  |  |  |  |  |  |  |  |  |
Line of credit facility, elected commitment |  |  |  |  |  |  | 1,000,000,000.0 |  | 1,000,000,000.0 |  |  |  |  |  |  |  |  |  |
Disposition costs, maximum expenses allowed |  |  |  |  |  |  |  |  | 3,000,000.0 |  |  |  |  |  |  |  |  |  |
Wells Fargo Bank | October Notes | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7.75%
Debt instrument, amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 250,000,000.0
Wells Fargo Bank | December Notes | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7.75% |
Debt instrument, amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,000,000.0 |
Wells Fargo Bank | August Notes | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7.75% |  |
Debt instrument, amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 300,000,000.0 |  |
InterBank | Revolving credit agreement | Construction loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 24,500,000.0 |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.50% |  |  |  |
InterBank | Letter of credit | Construction loans |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Required minimum down payment, percent |  |  |  |  |  | 30.00% |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 23,817,000 |  | $ 23,817,000 |  |  |  | $ 21,049,000 |  |  |  |  |  |

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- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + 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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- Definition Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -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 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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- 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: 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(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: 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 Reference 3: 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 + Details
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- Definition The cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585 + Details
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