| Condensed Consolidating Financial Information (Tables)
 | 9 Months Ended | 
| Sep. 30, 2014 | 
| Condensed Financial Information of Parent Company Only Disclosure [Abstract] |  | 
| Condensed Consolidating Balance Sheets | 
CONDENSED CONSOLIDATING BALANCE SHEETS 
(Amounts in thousands)
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | September 30, 2014 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
| Assets |   |   |   |   |   |   |   |   |   |  
| Current assets: |   |   |   |   |   |   |   |   |   |  
| Cash and cash equivalents | $ | 152,479 | 
 |   | $ | 404 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 152,883 | 
 |  
| Accounts receivable - oil and gas | 124,771 | 
 |   | 14,820 | 
 |   | — | 
 |   | — | 
 |   | 139,591 | 
 |  
| Accounts receivable - related parties | 153 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 153 | 
 |  
| Accounts receivable - intercompany | 36,679 | 
 |   | 27 | 
 |   | — | 
 |   | (36,706 | ) |   | — | 
 |  
| Prepaid expenses and other current assets | 3,578 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 3,578 | 
 |  
| Deferred tax asset | 7,819 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 7,819 | 
 |  
| Short-term derivative instruments | 5,753 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 5,753 | 
 |  
| Note receivable - related party | 875 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 875 | 
 |  
| Total current assets | 332,107 | 
 |   | 15,251 | 
 |   | — | 
 |   | (36,706 | ) |   | 310,652 | 
 |  
| Property and equipment: |   |   |   |   |   |   |   |   |   |  
| Oil and natural gas properties, full-cost accounting | 3,572,134 | 
 |   | 14,479 | 
 |   | — | 
 |   | (597 | ) |   | 3,586,016 | 
 |  
| Other property and equipment | 16,850 | 
 |   | 30 | 
 |   | — | 
 |   | — | 
 |   | 16,880 | 
 |  
| Accumulated depletion, depreciation, amortization and impairment | (969,938 | ) |   | (24 | ) |   | — | 
 |   | — | 
 |   | (969,962 | ) |  
| Property and equipment, net | 2,619,046 | 
 |   | 14,485 | 
 |   | — | 
 |   | (597 | ) |   | 2,632,934 | 
 |  
| Other assets: |   |   |   |   |   |   |   |   |   |  
| Equity investments and investments in subsidiaries | 363,851 | 
 |   | — | 
 |   | 189,182 | 
 |   | (179,818 | ) |   | 373,215 | 
 |  
| Derivative instruments | 1,156 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 1,156 | 
 |  
| Other assets | 23,430 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 23,430 | 
 |  
| Total other assets | 388,437 | 
 |   | — | 
 |   | 189,182 | 
 |   | (179,818 | ) |   | 397,801 | 
 |  
|   Total assets | $ | 3,339,590 | 
 |   | $ | 29,736 | 
 |   | $ | 189,182 | 
 |   | $ | (217,121 | ) |   | $ | 3,341,387 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Liabilities and Stockholders' Equity |   |   |   |   |   |   |   |   |   |  
| Current liabilities: |   |   |   |   |   |   |   |   |   |  
| Accounts payable and accrued liabilities | $ | 356,285 | 
 |   | $ | 1,797 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 358,082 | 
 |  
| Accounts payable - intercompany | — | 
 |   | 36,600 | 
 |   | 106 | 
 |   | (36,706 | ) |   | — | 
 |  
| Asset retirement obligation - current | 75 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 75 | 
 |  
| Short-term derivative instruments | 3,891 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 3,891 | 
 |  
| Current maturities of long-term debt | 166 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 166 | 
 |  
| Total current liabilities | 360,417 | 
 |   | 38,397 | 
 |   | 106 | 
 |   | (36,706 | ) |   | 362,214 | 
 |  
| Long-term derivative instrument | 2,771 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 2,771 | 
 |  
| Asset retirement obligation - long-term | 16,318 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 16,318 | 
 |  
| Deferred tax liability | 153,733 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 153,733 | 
 |  
| Long-term debt, net of current maturities | 616,881 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 616,881 | 
 |  
| Total liabilities | 1,150,120 | 
 |   | 38,397 | 
 |   | 106 | 
 |   | (36,706 | ) |   | 1,151,917 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Stockholders' equity: |   |   |   |   |   |   |   |   |   |  
| Common stock | 854 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 854 | 
 |  
| Paid-in capital | 1,824,955 | 
 |   | 322 | 
 |   | 224,849 | 
 |   | (225,171 | ) |   | 1,824,955 | 
 |  
| Accumulated other comprehensive income (loss) | (19,779 | ) |   | — | 
 |   | (19,779 | ) |   | 19,779 | 
 |   | (19,779 | ) |  
| Retained earnings (accumulated deficit) | 383,440 | 
 |   | (8,983 | ) |   | (15,994 | ) |   | 24,977 | 
 |   | 383,440 | 
 |  
| Total stockholders' equity | 2,189,470 | 
 |   | (8,661 | ) |   | 189,076 | 
 |   | (180,415 | ) |   | 2,189,470 | 
 |  
|   Total liabilities and stockholders' equity | $ | 3,339,590 | 
 |   | $ | 29,736 | 
 |   | $ | 189,182 | 
 |   | $ | (217,121 | ) |   | $ | 3,341,387 | 
 |  
CONDENSED CONSOLIDATING BALANCE SHEETS 
(Amounts in thousands)
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | December 31, 2013 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
| Assets |   |   |   |   |   |   |   |   |   |  
| Current assets: |   |   |   |   |   |   |   |   |   |  
| Cash and cash equivalents | $ | 451,431 | 
 |   | $ | 7,525 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 458,956 | 
 |  
| Accounts receivable - oil and gas | 58,662 | 
 |   | 162 | 
 |   | — | 
 |   | — | 
 |   | 58,824 | 
 |  
| Accounts receivable - related parties | 2,617 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 2,617 | 
 |  
| Accounts receivable - intercompany | 21,379 | 
 |   | 27 | 
 |   | — | 
 |   | (21,406 | ) |   | — | 
 |  
| Prepaid expenses and other current assets | 2,581 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 2,581 | 
 |  
| Deferred tax asset | 6,927 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 6,927 | 
 |  
| Short-term derivative instruments | 324 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 324 | 
 |  
| Note receivable - related party | 875 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 875 | 
 |  
| Total current assets | 544,796 | 
 |   | 7,714 | 
 |   | — | 
 |   | (21,406 | ) |   | 531,104 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Property and equipment: |   |   |   |   |   |   |   |   |   |  
| Oil and natural gas properties, full-cost accounting, | 2,470,411 | 
 |   | 7,340 | 
 |   | — | 
 |   | (573 | ) |   | 2,477,178 | 
 |  
| Other property and equipment | 11,102 | 
 |   | 29 | 
 |   | — | 
 |   | — | 
 |   | 11,131 | 
 |  
| Accumulated depletion, depreciation, amortization and impairment | (784,695 | ) |   | (22 | ) |   | — | 
 |   | — | 
 |   | (784,717 | ) |  
| Property and equipment, net | 1,696,818 | 
 |   | 7,347 | 
 |   | — | 
 |   | (573 | ) |   | 1,703,592 | 
 |  
| Other assets: |   |   |   |   |   |   |   |   |   |  
| Equity investments and investments in subsidiaries | 432,727 | 
 |   | — | 
 |   | 191,473 | 
 |   | (184,132 | ) |   | 440,068 | 
 |  
| Derivative instruments | 521 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 521 | 
 |  
| Other assets | 17,851 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 17,851 | 
 |  
| Total other assets | 451,099 | 
 |   | — | 
 |   | 191,473 | 
 |   | (184,132 | ) |   | 458,440 | 
 |  
|   Total assets | $ | 2,692,713 | 
 |   | $ | 15,061 | 
 |   | $ | 191,473 | 
 |   | $ | (206,111 | ) |   | $ | 2,693,136 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Liabilities and Stockholders' Equity |   |   |   |   |   |   |   |   |   |  
| Current liabilities: |   |   |   |   |   |   |   |   |   |  
| Accounts payable and accrued liabilities | $ | 190,284 | 
 |   | $ | 423 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 190,707 | 
 |  
| Accounts payable - intercompany | — | 
 |   | 21,296 | 
 |   | 110 | 
 |   | (21,406 | ) |   | — | 
 |  
| Asset retirement obligation - current | 795 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 795 | 
 |  
| Short-term derivative instruments | 12,280 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 12,280 | 
 |  
| Current maturities of long-term debt | 159 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 159 | 
 |  
| Total current liabilities | 203,518 | 
 |   | 21,719 | 
 |   | 110 | 
 |   | (21,406 | ) |   | 203,941 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Long-term derivative instrument | 11,366 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 11,366 | 
 |  
| Asset retirement obligation - long-term | 14,288 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 14,288 | 
 |  
| Deferred tax liability | 114,275 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 114,275 | 
 |  
| Long-term debt, net of current maturities | 299,028 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 299,028 | 
 |  
| Total liabilities | 642,475 | 
 |   | 21,719 | 
 |   | 110 | 
 |   | (21,406 | ) |   | 642,898 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Stockholders' equity: |   |   |   |   |   |   |   |   |   |  
| Common stock | 851 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 851 | 
 |  
| Paid-in capital | 1,813,058 | 
 |   | 322 | 
 |   | 208,277 | 
 |   | (208,599 | ) |   | 1,813,058 | 
 |  
| Accumulated other comprehensive income (loss) | (9,781 | ) |   | — | 
 |   | (9,781 | ) |   | 9,781 | 
 |   | (9,781 | ) |  
| Retained earnings (accumulated deficit) | 246,110 | 
 |   | (6,980 | ) |   | (7,133 | ) |   | 14,113 | 
 |   | 246,110 | 
 |  
| Total stockholders' equity | 2,050,238 | 
 |   | (6,658 | ) |   | 191,363 | 
 |   | (184,705 | ) |   | 2,050,238 | 
 |  
|   Total liabilities and stockholders' equity | $ | 2,692,713 | 
 |   | $ | 15,061 | 
 |   | $ | 191,473 | 
 |   | $ | (206,111 | ) |   | $ | 2,693,136 | 
 |  | 
| Condensed Consolidating Statements of Operations | 
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Amounts in thousands) 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Three months ended September 30, 2014 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Total revenues | $ | 170,284 | 
 |   | $ | 520 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 170,804 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Costs and expenses: |   |   |   |   |   |   |   |   |   |  
| Lease operating expenses | 11,628 | 
 |   | 255 | 
 |   | — | 
 |   | — | 
 |   | 11,883 | 
 |  
| Production taxes | 5,154 | 
 |   | 59 | 
 |   | — | 
 |   | — | 
 |   | 5,213 | 
 |  
| Midstream processing and marketing | 18,694 | 
 |   | 20 | 
 |   | — | 
 |   | — | 
 |   | 18,714 | 
 |  
| Depreciation, depletion, and amortization | 72,408 | 
 |   | 1 | 
 |   | — | 
 |   | — | 
 |   | 72,409 | 
 |  
| General and administrative | 8,909 | 
 |   | 29 | 
 |   | 1 | 
 |   | — | 
 |   | 8,939 | 
 |  
| Accretion expense | 192 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 192 | 
 |  
|   | 116,985 | 
 |   | 364 | 
 |   | 1 | 
 |   | — | 
 |   | 117,350 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| INCOME (LOSS) FROM OPERATIONS | 53,299 | 
 |   | 156 | 
 |   | (1 | ) |   | — | 
 |   | 53,454 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| OTHER (INCOME) EXPENSE: |   |   |   |   |   |   |   |   |   |  
| Interest expense | 5,706 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 5,706 | 
 |  
| Interest income | (25 | ) |   | — | 
 |   | — | 
 |   | — | 
 |   | (25 | ) |  
| Litigation settlement | 1,500 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 1,500 | 
 |  
| Loss (income) from equity method investments and investments in subsidiaries | 34,322 | 
 |   | — | 
 |   | 4,633 | 
 |   | (4,478 | ) |   | 34,477 | 
 |  
|   | 41,503 | 
 |   | — | 
 |   | 4,633 | 
 |   | (4,478 | ) |   | 41,658 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| INCOME (LOSS) BEFORE INCOME TAXES | 11,796 | 
 |   | 156 | 
 |   | (4,634 | ) |   | 4,478 | 
 |   | 11,796 | 
 |  
| INCOME TAX EXPENSE | 4,876 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 4,876 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| NET INCOME (LOSS) | $ | 6,920 | 
 |   | $ | 156 | 
 |   | $ | (4,634 | ) |   | $ | 4,478 | 
 |   | $ | 6,920 | 
 |  
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Amounts in thousands) 
 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Three months ended September 30, 2013 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Total revenues | $ | 68,855 | 
 |   | $ | 397 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 69,252 | 
 |  
|   |   |   |   |   |   |   |   |   | 
 | 
 |  
| Costs and expenses: |   |   |   |   |   |   |   |   | 
 | 
 |  
| Lease operating expenses | 7,137 | 
 |   | 160 | 
 |   | — | 
 |   | — | 
 |   | 7,297 | 
 |  
| Production taxes | 7,050 | 
 |   | 21 | 
 |   | — | 
 |   | — | 
 |   | 7,071 | 
 |  
| Midstream processing and marketing | 3,616 | 
 |   | 6 | 
 |   | — | 
 |   | — | 
 |   | 3,622 | 
 |  
| Depreciation, depletion, and amortization | 30,691 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 30,691 | 
 |  
| General and administrative | 5,229 | 
 |   | 31 | 
 |   | (1 | ) |   | — | 
 |   | 5,259 | 
 |  
| Accretion expense | 180 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 180 | 
 |  
| Loss on sale of assets | (5 | ) |   | — | 
 |   | — | 
 |   | — | 
 |   | (5 | ) |  
|   | 53,898 | 
 | 
 | 218 | 
 | 
 | (1 | ) | 
 | — | 
 | 
 | 54,115 | 
 |  
|   | 
 | 
 | 
 | 
 | 
 | 
 | 
 | 
 |   |  
| INCOME FROM OPERATIONS | 14,957 | 
 | 
 | 179 | 
 | 
 | 1 | 
 | 
 | — | 
 | 
 | 15,137 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| OTHER (INCOME) EXPENSE: |   |   |   |   |   |   |   |   |   |  
| Interest expense | 2,602 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 2,602 | 
 |  
| Interest income | (70 | ) |   | — | 
 |   | — | 
 |   | — | 
 |   | (70 | ) |  
| (Income) loss from equity method investments and investments in subsidiaries | (51,502 | ) |   | — | 
 |   | 863 | 
 |   | (683 | ) |   | (51,322 | ) |  
|   | (48,970 | ) | 
 | — | 
 | 
 | 863 | 
 | 
 | (683 | ) | 
 | (48,790 | ) |  
|   |   |   |   |   |   |   |   |   |   |  
| INCOME (LOSS) BEFORE INCOME TAXES | 63,927 | 
 | 
 | 179 | 
 | 
 | (862 | ) | 
 | 683 | 
 | 
 | 63,927 | 
 |  
| INCOME TAX EXPENSE | 23,400 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 23,400 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| NET INCOME (LOSS) | $ | 40,527 | 
 | 
 | $ | 179 | 
 | 
 | $ | (862 | ) | 
 | $ | 683 | 
 | 
 | $ | 40,527 | 
 |  
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Amounts in thousands) 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Nine months ended September 30, 2014 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Total revenues | $ | 402,148 | 
 |   | $ | 1,421 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 403,569 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Costs and expenses: |   |   |   |   |   |   |   |   |   |  
| Lease operating expenses | 35,466 | 
 |   | 726 | 
 |   | — | 
 |   | — | 
 |   | 36,192 | 
 |  
| Production taxes | 18,620 | 
 |   | 151 | 
 |   | — | 
 |   | — | 
 |   | 18,771 | 
 |  
| Midstream processing and marketing | 37,209 | 
 |   | 54 | 
 |   | — | 
 |   | — | 
 |   | 37,263 | 
 |  
| Depreciation, depletion, and amortization | 185,278 | 
 |   | 2 | 
 |   | — | 
 |   | — | 
 |   | 185,280 | 
 |  
| General and administrative | 28,743 | 
 |   | 91 | 
 |   | (2 | ) |   | — | 
 |   | 28,832 | 
 |  
| Accretion expense | 569 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 569 | 
 |  
| Gain on sale of assets | (11 | ) |   | — | 
 |   | — | 
 |   | — | 
 |   | (11 | ) |  
|   | 305,874 | 
 |   | 1,024 | 
 |   | (2 | ) |   | — | 
 |   | 306,896 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| INCOME FROM OPERATIONS | 96,274 | 
 |   | 397 | 
 |   | 2 | 
 |   | — | 
 |   | 96,673 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| OTHER (INCOME) EXPENSE: |   |   |   |   |   |   |   |   |   |  
| Interest expense | 11,993 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 11,993 | 
 |  
| Interest income | (167 | ) |   | — | 
 |   | — | 
 |   | — | 
 |   | (167 | ) |  
| Litigation settlement | 25,500 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 25,500 | 
 |  
| (Income) loss from equity method investments and investments in subsidiaries | (163,966 | ) |   | — | 
 |   | 8,862 | 
 |   | (8,463 | ) |   | (163,567 | ) |  
|   | (126,640 | ) |   | — | 
 |   | 8,862 | 
 |   | (8,463 | ) |   | (126,241 | ) |  
|   |   |   |   |   |   |   |   |   |   |  
| INCOME (LOSS) BEFORE INCOME TAXES | 222,914 | 
 |   | 397 | 
 |   | (8,860 | ) |   | 8,463 | 
 |   | 222,914 | 
 |  
| INCOME TAX EXPENSE | 85,584 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 85,584 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| NET INCOME (LOSS) | $ | 137,330 | 
 |   | $ | 397 | 
 |   | $ | (8,860 | ) |   | $ | 8,463 | 
 |   | $ | 137,330 | 
 |  
CONDENSED CONSOLIDATING STATEMENTS OF OPERATIONS (Amounts in thousands) 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Nine months ended September 30, 2013 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Total revenues | $ | 193,550 | 
 |   | $ | 1,136 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 194,686 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Costs and expenses: |   |   |   |   |   |   |   |   |   |  
| Lease operating expenses | 17,849 | 
 |   | 498 | 
 |   | — | 
 |   | — | 
 |   | 18,347 | 
 |  
| Production taxes | 20,317 | 
 |   | 64 | 
 |   | — | 
 |   | — | 
 |   | 20,381 | 
 |  
| Midstream processing and marketing | 5,926 | 
 |   | 14 | 
 |   | — | 
 |   | — | 
 |   | 5,940 | 
 |  
| Depreciation, depletion, and amortization | 81,813 | 
 |   | 1 | 
 |   | — | 
 |   | — | 
 |   | 81,814 | 
 |  
| General and administrative | 14,466 | 
 |   | 103 | 
 |   | 2 | 
 |   | — | 
 |   | 14,571 | 
 |  
| Accretion expense | 529 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 529 | 
 |  
| Loss on sale of assets | 567 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 567 | 
 |  
|   | 141,467 | 
 |   | 680 | 
 |   | 2 | 
 |   | — | 
 |   | 142,149 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| INCOME (LOSS) FROM OPERATIONS | 52,083 | 
 |   | 456 | 
 |   | (2 | ) |   | — | 
 |   | 52,537 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| OTHER (INCOME) EXPENSE: |   |   |   |   |   |   |   |   |   |  
| Interest expense | 9,365 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 9,365 | 
 |  
| Interest income | (211 | ) |   | — | 
 |   | — | 
 |   | — | 
 |   | (211 | ) |  
| (Income) loss from equity method investments and investments in subsidiaries | (163,094 | ) |   | — | 
 |   | 2,125 | 
 |   | (1,671 | ) |   | (162,640 | ) |  
|   | (153,940 | ) |   | — | 
 |   | 2,125 | 
 |   | (1,671 | ) |   | (153,486 | ) |  
|   |   |   |   |   |   |   |   |   |   |  
| INCOME (LOSS) BEFORE INCOME TAXES | 206,023 | 
 |   | 456 | 
 |   | (2,127 | ) |   | 1,671 | 
 |   | 206,023 | 
 |  
| INCOME TAX EXPENSE | 77,109 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 77,109 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| NET INCOME (LOSS) | $ | 128,914 | 
 |   | $ | 456 | 
 |   | $ | (2,127 | ) |   | $ | 1,671 | 
 |   | $ | 128,914 | 
 |  | 
| Condensed Consolidating Statements of Comprehensive Income (Loss) | 
CONDENSED CONSOLIDATING STATEMENTS OF COMPREHENSIVE INCOME (LOSS)  (Amounts in thousands) 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Three months ended September 30, 2014 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Net income (loss) | $ | 6,920 | 
 |   | $ | 156 | 
 |   | $ | (4,634 | ) |   | $ | 4,478 | 
 |   | $ | 6,920 | 
 |  
| Foreign currency translation adjustment | (9,536 | ) |   | — | 
 |   | (9,536 | ) |   | 9,536 | 
 |   | (9,536 | ) |  
| Other comprehensive income (loss) | (9,536 | ) |   | — | 
 |   | (9,536 | ) |   | 9,536 | 
 |   | (9,536 | ) |  
| Comprehensive income (loss) | $ | (2,616 | ) |   | $ | 156 | 
 |   | $ | (14,170 | ) |   | $ | 14,014 | 
 |   | $ | (2,616 | ) |  
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Three months ended September 30, 2013 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |  
| Net income (loss) | $ | 40,527 | 
 |   | $ | 179 | 
 |   | $ | (862 | ) |   | $ | 683 | 
 |   | $ | 40,527 | 
 |  
| Foreign currency translation adjustment | 3,894 | 
 |   | — | 
 |   | 3,894 | 
 |   | (3,894 | ) |   | 3,894 | 
 |  
| Change in fair value of derivative instruments, net of taxes | 630 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 630 | 
 |  
| Reclassification of settled contracts, net of taxes | 1,617 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 1,617 | 
 |  
| Other comprehensive income (loss) | 6,141 | 
 |   | — | 
 |   | 3,894 | 
 |   | (3,894 | ) |   | 6,141 | 
 |  
| Comprehensive income (loss) | $ | 46,668 | 
 |   | $ | 179 | 
 |   | $ | 3,032 | 
 |   | $ | (3,211 | ) |   | $ | 46,668 | 
 | 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Nine months ended September 30, 2014 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Net income (loss) | $ | 137,330 | 
 |   | $ | 397 | 
 |   | $ | (8,860 | ) |   | $ | 8,463 | 
 |   | $ | 137,330 | 
 |  
| Foreign currency translation adjustment | (9,998 | ) |   | — | 
 |   | (9,998 | ) |   | 9,998 | 
 |   | (9,998 | ) |  
| Other comprehensive income (loss) | (9,998 | ) |   | — | 
 |   | (9,998 | ) |   | 9,998 | 
 |   | (9,998 | ) |  
| Comprehensive income (loss) | $ | 127,332 | 
 |   | $ | 397 | 
 |   | $ | (18,858 | ) |   | $ | 18,461 | 
 |   | $ | 127,332 | 
 | 
 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Nine months ended September 30, 2013 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |  
| Net income (loss) | $ | 128,914 | 
 |   | $ | 456 | 
 |   | $ | (2,127 | ) |   | $ | 1,671 | 
 |   | $ | 128,914 | 
 |  
| Foreign currency translation adjustment | (5,786 | ) |   | — | 
 |   | (5,786 | ) |   | 5,786 | 
 |   | (5,786 | ) |  
| Change in fair value of derivative instruments, net of taxes | (444 | ) |   | — | 
 |   | — | 
 |   | — | 
 |   | (444 | ) |  
| Reclassification of settled contracts, net of taxes | 4,818 | 
 |   | — | 
 |   | — | 
 |   | — | 
 |   | 4,818 | 
 |  
| Other comprehensive income (loss) | (1,412 | ) |   | — | 
 |   | (5,786 | ) |   | 5,786 | 
 |   | (1,412 | ) |  
| Comprehensive income (loss) | $ | 127,502 | 
 |   | $ | 456 | 
 |   | $ | (7,913 | ) |   | $ | 7,457 | 
 |   | $ | 127,502 | 
 |  | 
| Condensed Consolidating Statements of Cash Flows | 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Nine months ended September 30, 2014 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Net cash provided by (used in) operating activities | $ | 286,500 | 
 |   | $ | (598 | ) |   | $ | (3 | ) |   | $ | — | 
 |   | $ | 285,899 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Net cash provided by (used in) investing activities | (897,527 | ) |   | (6,523 | ) |   | (16,569 | ) |   | 16,572 | 
 |   | (904,047 | ) |  
|   |   |   |   |   |   |   |   |   |   |  
| Net cash provided by (used in) financing activities | 312,075 | 
 |   | — | 
 |   | 16,572 | 
 |   | (16,572 | ) |   | 312,075 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Net decrease in cash and cash equivalents | (298,952 | ) |   | (7,121 | ) |   | — | 
 |   | — | 
 |   | (306,073 | ) |  
|   |   |   |   |   |   |   |   |   |   |  
| Cash and cash equivalents at beginning of period | 451,431 | 
 |   | 7,525 | 
 |   | — | 
 |   | — | 
 |   | 458,956 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Cash and cash equivalents at end of period | $ | 152,479 | 
 |   | $ | 404 | 
 |   | $ | — | 
 |   | $ | — | 
 |   | $ | 152,883 | 
 | 
 
|  |  
|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  
|   | Nine months ended September 30, 2013 |  
|   | Parent |   | Guarantors |   | Non-Guarantor |   | Eliminations |   | Consolidated |  
|   |   |   |   |   |   |   |   |   |   |  
| Net cash provided by (used in) operating activities | $ | 139,818 | 
 |   | $ | 1,213 | 
 |   | $ | (1 | ) |   | $ | — | 
 |   | $ | 141,030 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Net cash provided by (used in) investing activities | (569,291 | ) |   | (1,539 | ) |   | (25,087 | ) |   | 25,089 | 
 |   | (570,828 | ) |  
|   |   |   |   |   |   |   |   |   |   |  
| Net cash provided by (used in) financing activities | 358,176 | 
 |   | — | 
 |   | 25,089 | 
 |   | (25,089 | ) |   | 358,176 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Net increase (decrease) in cash and cash equivalents | (71,297 | ) |   | (326 | ) |   | 1 | 
 |   | — | 
 |   | (71,622 | ) |  
|   |   |   |   |   |   |   |   |   |   |  
| Cash and cash equivalents at beginning of period | 165,293 | 
 |   | 1,795 | 
 |   | — | 
 |   | — | 
 |   | 167,088 | 
 |  
|   |   |   |   |   |   |   |   |   |   |  
| Cash and cash equivalents at end of period | $ | 93,996 | 
 |   | $ | 1,469 | 
 |   | $ | 1 | 
 |   | $ | — | 
 |   | $ | 95,466 | 
 |  |