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LONG-TERM DEBT (Narrative) (Details) |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
May 21, 2018 USD ($) | Nov. 21, 2017 | May 04, 2017 USD ($) bank | Dec. 21, 2016 USD ($) | Oct. 14, 2016 USD ($) | Jan. 31, 2016 | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2018 USD ($) | Sep. 30, 2017 USD ($) | Dec. 31, 2017 USD ($) | Oct. 11, 2017 USD ($) | May 05, 2017 USD ($) | Mar. 29, 2017 USD ($) | Jun. 04, 2015 USD ($) | Apr. 21, 2015 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capitalized interest expense, undeveloped properties |  |  |  |  |  |  | $ 1,600,000 | $ 2,100,000 | $ 4,000,000 | $ 8,800,000 |  |  |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | 31,824,000 |  | 31,824,000 |  | $ 34,781,000 |  |  |  |  |
Construction loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | $ 100,000 |  | $ 100,000 |  |  |  |  |  |  |
Revolving credit agreement | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt covenant ratio for future EBITDAX |  |  |  |  |  |  | 4.00 |  | 4.00 |  |  |  |  |  |  |
Revolving credit agreement | Revolving credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt covenant ratio for EBITDAX |  |  |  |  |  |  | 3.00 |  | 3.00 |  |  |  |  |  |  |
6.000% senior unsecured 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% |  |  |  |  |  |  |
Debt instrument, amount |  |  |  |  | $ 650,000,000.0 |  |  |  |  |  |  |  |  |  |  |
Proceeds from issuance of Senior Notes |  |  |  |  | $ 638,900,000 |  |  |  |  |  |  |  |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | $ 9,000,000 |  | $ 9,000,000 |  |  |  |  |  |  |
6.625% senior unsecured 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 |  |  |  |  |  |  | $ 4,600,000 |  | $ 4,600,000 |  |  |  |  |  |  |
6.375% senior unsecured 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 |  |  |  |  |  |  | $ 12,900,000 |  | $ 12,900,000 |  |  |  |  |  |  |
6.375% senior unsecured notes due 2026 | Senior notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 450,000,000 |  | $ 450,000,000 |  | 450,000,000 |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 6.375% |  | 6.375% |  |  | 6.375% |  |  |  |
Debt instrument, amount |  |  |  |  |  |  |  |  |  |  |  | $ 450,000,000.0 |  |  |  |
Long term debt, net of initial purchaser discounts and commissions and estimated offering expenses |  |  |  |  |  |  |  |  |  |  |  | $ 444,100,000 |  |  |  |
Debt issuance costs, net |  |  |  |  |  |  | $ 5,200,000 |  | $ 5,200,000 |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Credit facility interest rate at the eurodollar rate |  |  |  |  |  |  |  |  | 3.72% |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Base rate | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 0.25% |  | 0.25% |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Base rate | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 1.25% |  | 1.25% |  |  |  |  |  |  |
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 rate |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis spread, percent |  |  |  |  |  |  |  |  | 1.00% |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Eurodollar rate | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 1.25% |  | 1.25% |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Eurodollar rate | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stated interest rate, percent |  |  |  |  |  |  | 2.25% |  | 2.25% |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Revolving credit agreement | Revolving credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 60,000,000 |  | $ 60,000,000 |  | 0 |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  | 1,500,000,000.0 |  | 1,500,000,000.0 |  |  |  |  |  |  |
Minimum acquisition payment limit |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,000,000 |  |
Minimum disposition of property limit |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 50,000,000 |  |
Borrowing base | $ 1,400,000,000 |  | $ 700,000,000 |  |  |  | 1,200,000,000 |  | 1,200,000,000 |  |  |  | $ 1,000,000,000 |  |  |
Number of banks added to syndicate (in banks) | bank |  |  | 5 |  |  |  |  |  |  |  |  |  |  |  |  |
Increase (decrease) in interest rate | 0.25% | 0.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Remaining borrowing capacity |  |  |  |  |  |  | 623,800,000 |  | 623,800,000 |  |  |  |  |  |  |
Nova Scotia, Amegy, KeyBank | Letter of credit | Revolving credit agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Line of credit facility, elected commitment | $ 1,000,000,000.0 |  |  |  |  |  | 1,000,000,000.0 |  | 1,000,000,000.0 |  |  |  |  |  |  |
Credit facility outstanding |  |  |  |  |  |  | 316,200,000 |  | 316,200,000 |  |  |  |  |  |  |
Disposition costs, maximum expenses allowed |  |  |  |  |  |  |  |  | 3,000,000.0 |  |  |  |  |  |  |
InterBank | Revolving credit agreement | Construction loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum borrowing capacity |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 24,500,000.0 |
Stated interest rate, percent |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.50% |
InterBank | Letter of credit | Construction loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Long-term debt |  |  |  |  |  |  | $ 23,296,000 |  | $ 23,296,000 |  | $ 23,724,000 |  |  |  |  |
Required minimum down payment, percent |  |  |  |  |  | 30.00% |  |  |  |  |  |  |  |  |  |

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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/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -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://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 4: http://fasb.org/us-gaap/role/ref/legacyRef -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 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://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 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://fasb.org/us-gaap/role/ref/legacyRef -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 + Details
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