Condensed Consolidating Financial Information - Balance Sheets (Details) - USD ($)
   | 
Dec. 31, 2018  | 
Dec. 31, 2017  | 
Dec. 31, 2016  | 
Dec. 31, 2015  | 
| Current assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Cash and cash equivalents | 
$ 52,297,000
 | 
$ 99,557,000
 | 
 
 | 
 
 | 
| Accounts receivable—oil and natural gas sales | 
210,200,000
 | 
146,773,000
 | 
 
 | 
 
 | 
| Accounts receivable - joint interest and other | 
22,497,000
 | 
35,440,000
 | 
 
 | 
 
 | 
| Accounts receivable - intercompany | 
0
 | 
0
 | 
 
 | 
 
 | 
| Prepaid expenses and other current assets | 
10,607,000
 | 
4,912,000
 | 
 
 | 
 
 | 
| Short-term derivative instruments - asset | 
21,352,000
 | 
78,847,000
 | 
 
 | 
 
 | 
| Total current assets | 
316,953,000
 | 
365,529,000
 | 
 
 | 
 
 | 
| Property and equipment: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Oil and natural gas properties, full-cost accounting | 
10,026,836,000
 | 
9,169,156,000
 | 
 
 | 
 
 | 
| Other property and equipment | 
92,667,000
 | 
86,754,000
 | 
 
 | 
 
 | 
| Accumulated depletion, depreciation, amortization and impairment | 
(4,640,098,000)
 | 
(4,153,733,000)
 | 
 
 | 
 
 | 
| Property and equipment, net | 
5,479,405,000
 | 
5,102,177,000
 | 
 
 | 
 
 | 
| Other assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Equity investments and investments in subsidiaries | 
236,121,000
 | 
302,112,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
0
 | 
8,685,000
 | 
 
 | 
 
 | 
| Deferred tax asset | 
0
 | 
1,208,000
 | 
 
 | 
 
 | 
| Inventories | 
4,754,000
 | 
8,227,000
 | 
 
 | 
 
 | 
| Other assets | 
13,803,000
 | 
19,814,000
 | 
 
 | 
 
 | 
| Total other assets | 
254,678,000
 | 
340,046,000
 | 
 
 | 
 
 | 
| Total assets | 
6,051,036,000
 | 
5,807,752,000
 | 
 
 | 
 
 | 
| Current liabilities: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Accounts payable and accrued liabilities | 
518,380,000
 | 
553,609,000
 | 
 
 | 
 
 | 
| Accounts payable - intercompany | 
0
 | 
0
 | 
 
 | 
 
 | 
| Asset retirement obligation—current | 
0
 | 
120,000
 | 
 
 | 
 
 | 
| Short-term derivative instruments | 
20,401,000
 | 
32,534,000
 | 
 
 | 
 
 | 
| Current maturities of long-term debt | 
651,000
 | 
622,000
 | 
 
 | 
 
 | 
| Total current liabilities | 
539,432,000
 | 
586,885,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
13,992,000
 | 
2,989,000
 | 
 
 | 
 
 | 
| Asset retirement obligation—long-term | 
79,952,000
 | 
74,980,000
 | 
 
 | 
 
 | 
| Deferred tax liability | 
3,127,000
 | 
0
 | 
 
 | 
 
 | 
| Other non-current liabilities | 
0
 | 
2,963,000
 | 
 
 | 
 
 | 
| Long-term debt, net of current maturities | 
2,086,765,000
 | 
2,038,321,000
 | 
 
 | 
 
 | 
| Total liabilities | 
2,723,268,000
 | 
2,706,138,000
 | 
 
 | 
 
 | 
| Stockholders’ equity: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Common stock | 
1,630,000
 | 
1,831,000
 | 
 
 | 
 
 | 
| Paid-in capital | 
4,227,532,000
 | 
4,416,250,000
 | 
 
 | 
 
 | 
| Accumulated other comprehensive loss | 
(56,026,000)
 | 
(40,539,000)
 | 
 
 | 
 
 | 
| (Accumulated deficit) retained earnings | 
(845,368,000)
 | 
(1,275,928,000)
 | 
 
 | 
 
 | 
| Total stockholders’ equity | 
3,327,768,000
 | 
3,101,614,000
 | 
$ 2,183,892,000
 | 
$ 2,038,837,000
 | 
| Total liabilities and stockholders’ equity | 
6,051,036,000
 | 
5,807,752,000
 | 
 
 | 
 
 | 
| Eliminations | 
 
 | 
 
 | 
 
 | 
 
 | 
| Current assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Cash and cash equivalents | 
0
 | 
0
 | 
 
 | 
 
 | 
| Accounts receivable—oil and natural gas sales | 
 
 | 
0
 | 
 
 | 
 
 | 
| Accounts receivable - joint interest and other | 
0
 | 
0
 | 
 
 | 
 
 | 
| Accounts receivable - intercompany | 
(991,097,000)
 | 
(617,813,000)
 | 
 
 | 
 
 | 
| Prepaid expenses and other current assets | 
0
 | 
0
 | 
 
 | 
 
 | 
| Short-term derivative instruments - asset | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total current assets | 
(991,097,000)
 | 
(617,813,000)
 | 
 
 | 
 
 | 
| Property and equipment: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Oil and natural gas properties, full-cost accounting | 
(729,000)
 | 
(729,000)
 | 
 
 | 
 
 | 
| Other property and equipment | 
0
 | 
0
 | 
 
 | 
 
 | 
| Accumulated depletion, depreciation, amortization and impairment | 
0
 | 
0
 | 
 
 | 
 
 | 
| Property and equipment, net | 
(729,000)
 | 
(729,000)
 | 
 
 | 
 
 | 
| Other assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Equity investments and investments in subsidiaries | 
(2,665,126,000)
 | 
(2,194,848,000)
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
 
 | 
0
 | 
 
 | 
 
 | 
| Deferred tax asset | 
 
 | 
0
 | 
 
 | 
 
 | 
| Inventories | 
0
 | 
0
 | 
 
 | 
 
 | 
| Other assets | 
1,000
 | 
0
 | 
 
 | 
 
 | 
| Total other assets | 
(2,665,125,000)
 | 
(2,194,848,000)
 | 
 
 | 
 
 | 
| Total assets | 
(3,656,951,000)
 | 
(2,813,390,000)
 | 
 
 | 
 
 | 
| Current liabilities: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Accounts payable and accrued liabilities | 
 
 | 
(1,000)
 | 
 
 | 
 
 | 
| Accounts payable - intercompany | 
(991,097,000)
 | 
(617,813,000)
 | 
 
 | 
 
 | 
| Asset retirement obligation—current | 
 
 | 
0
 | 
 
 | 
 
 | 
| Short-term derivative instruments | 
0
 | 
0
 | 
 
 | 
 
 | 
| Current maturities of long-term debt | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total current liabilities | 
(991,097,000)
 | 
(617,814,000)
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
0
 | 
0
 | 
 
 | 
 
 | 
| Asset retirement obligation—long-term | 
0
 | 
0
 | 
 
 | 
 
 | 
| Deferred tax liability | 
0
 | 
 
 | 
 
 | 
 
 | 
| Other non-current liabilities | 
 
 | 
0
 | 
 
 | 
 
 | 
| Long-term debt, net of current maturities | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total liabilities | 
(991,097,000)
 | 
(617,814,000)
 | 
 
 | 
 
 | 
| Stockholders’ equity: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Common stock | 
0
 | 
0
 | 
 
 | 
 
 | 
| Paid-in capital | 
(2,177,224,000)
 | 
(2,174,905,000)
 | 
 
 | 
 
 | 
| Accumulated other comprehensive loss | 
53,783,000
 | 
38,593,000
 | 
 
 | 
 
 | 
| (Accumulated deficit) retained earnings | 
(542,413,000)
 | 
(59,264,000)
 | 
 
 | 
 
 | 
| Total stockholders’ equity | 
(2,665,854,000)
 | 
(2,195,576,000)
 | 
 
 | 
 
 | 
| Total liabilities and stockholders’ equity | 
(3,656,951,000)
 | 
(2,813,390,000)
 | 
 
 | 
 
 | 
| Parent | 
 
 | 
 
 | 
 
 | 
 
 | 
| Current assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Cash and cash equivalents | 
25,585,000
 | 
67,908,000
 | 
 
 | 
 
 | 
| Accounts receivable—oil and natural gas sales | 
146,075,000
 | 
112,686,000
 | 
 
 | 
 
 | 
| Accounts receivable - joint interest and other | 
16,212,000
 | 
15,435,000
 | 
 
 | 
 
 | 
| Accounts receivable - intercompany | 
671,633,000
 | 
554,439,000
 | 
 
 | 
 
 | 
| Prepaid expenses and other current assets | 
8,433,000
 | 
4,719,000
 | 
 
 | 
 
 | 
| Short-term derivative instruments - asset | 
21,352,000
 | 
78,847,000
 | 
 
 | 
 
 | 
| Total current assets | 
889,290,000
 | 
834,034,000
 | 
 
 | 
 
 | 
| Property and equipment: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Oil and natural gas properties, full-cost accounting | 
7,044,550,000
 | 
6,562,147,000
 | 
 
 | 
 
 | 
| Other property and equipment | 
91,916,000
 | 
86,711,000
 | 
 
 | 
 
 | 
| Accumulated depletion, depreciation, amortization and impairment | 
(4,640,059,000)
 | 
(4,153,696,000)
 | 
 
 | 
 
 | 
| Property and equipment, net | 
2,496,407,000
 | 
2,495,162,000
 | 
 
 | 
 
 | 
| Other assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Equity investments and investments in subsidiaries | 
2,856,988,000
 | 
2,361,575,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
 
 | 
8,685,000
 | 
 
 | 
 
 | 
| Deferred tax asset | 
 
 | 
1,208,000
 | 
 
 | 
 
 | 
| Inventories | 
3,620,000
 | 
5,816,000
 | 
 
 | 
 
 | 
| Other assets | 
12,624,000
 | 
12,483,000
 | 
 
 | 
 
 | 
| Total other assets | 
2,873,232,000
 | 
2,389,767,000
 | 
 
 | 
 
 | 
| Total assets | 
6,258,929,000
 | 
5,718,963,000
 | 
 
 | 
 
 | 
| Current liabilities: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Accounts payable and accrued liabilities | 
419,107,000
 | 
416,249,000
 | 
 
 | 
 
 | 
| Accounts payable - intercompany | 
320,259,000
 | 
63,373,000
 | 
 
 | 
 
 | 
| Asset retirement obligation—current | 
 
 | 
120,000
 | 
 
 | 
 
 | 
| Short-term derivative instruments | 
20,401,000
 | 
32,534,000
 | 
 
 | 
 
 | 
| Current maturities of long-term debt | 
651,000
 | 
622,000
 | 
 
 | 
 
 | 
| Total current liabilities | 
760,418,000
 | 
512,898,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
13,992,000
 | 
2,989,000
 | 
 
 | 
 
 | 
| Asset retirement obligation—long-term | 
66,859,000
 | 
63,141,000
 | 
 
 | 
 
 | 
| Deferred tax liability | 
3,127,000
 | 
 
 | 
 
 | 
 
 | 
| Other non-current liabilities | 
 
 | 
0
 | 
 
 | 
 
 | 
| Long-term debt, net of current maturities | 
2,086,765,000
 | 
2,038,321,000
 | 
 
 | 
 
 | 
| Total liabilities | 
2,931,161,000
 | 
2,617,349,000
 | 
 
 | 
 
 | 
| Stockholders’ equity: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Common stock | 
1,630,000
 | 
1,831,000
 | 
 
 | 
 
 | 
| Paid-in capital | 
4,227,532,000
 | 
4,416,250,000
 | 
 
 | 
 
 | 
| Accumulated other comprehensive loss | 
(56,026,000)
 | 
(40,539,000)
 | 
 
 | 
 
 | 
| (Accumulated deficit) retained earnings | 
(845,368,000)
 | 
(1,275,928,000)
 | 
 
 | 
 
 | 
| Total stockholders’ equity | 
3,327,768,000
 | 
3,101,614,000
 | 
 
 | 
 
 | 
| Total liabilities and stockholders’ equity | 
6,258,929,000
 | 
5,718,963,000
 | 
 
 | 
 
 | 
| Guarantors | 
 
 | 
 
 | 
 
 | 
 
 | 
| Current assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Cash and cash equivalents | 
26,711,000
 | 
31,649,000
 | 
 
 | 
 
 | 
| Accounts receivable—oil and natural gas sales | 
64,125,000
 | 
34,087,000
 | 
 
 | 
 
 | 
| Accounts receivable - joint interest and other | 
6,285,000
 | 
20,005,000
 | 
 
 | 
 
 | 
| Accounts receivable - intercompany | 
319,464,000
 | 
63,374,000
 | 
 
 | 
 
 | 
| Prepaid expenses and other current assets | 
2,174,000
 | 
193,000
 | 
 
 | 
 
 | 
| Short-term derivative instruments - asset | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total current assets | 
418,759,000
 | 
149,308,000
 | 
 
 | 
 
 | 
| Property and equipment: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Oil and natural gas properties, full-cost accounting | 
2,983,015,000
 | 
2,607,738,000
 | 
 
 | 
 
 | 
| Other property and equipment | 
751,000
 | 
43,000
 | 
 
 | 
 
 | 
| Accumulated depletion, depreciation, amortization and impairment | 
(39,000)
 | 
(37,000)
 | 
 
 | 
 
 | 
| Property and equipment, net | 
2,983,727,000
 | 
2,607,744,000
 | 
 
 | 
 
 | 
| Other assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Equity investments and investments in subsidiaries | 
0
 | 
77,744,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
 
 | 
0
 | 
 
 | 
 
 | 
| Deferred tax asset | 
 
 | 
0
 | 
 
 | 
 
 | 
| Inventories | 
1,134,000
 | 
2,411,000
 | 
 
 | 
 
 | 
| Other assets | 
1,178,000
 | 
7,331,000
 | 
 
 | 
 
 | 
| Total other assets | 
2,312,000
 | 
87,486,000
 | 
 
 | 
 
 | 
| Total assets | 
3,404,798,000
 | 
2,844,538,000
 | 
 
 | 
 
 | 
| Current liabilities: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Accounts payable and accrued liabilities | 
99,273,000
 | 
137,361,000
 | 
 
 | 
 
 | 
| Accounts payable - intercompany | 
670,708,000
 | 
554,313,000
 | 
 
 | 
 
 | 
| Asset retirement obligation—current | 
 
 | 
0
 | 
 
 | 
 
 | 
| Short-term derivative instruments | 
0
 | 
0
 | 
 
 | 
 
 | 
| Current maturities of long-term debt | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total current liabilities | 
769,981,000
 | 
691,674,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
0
 | 
0
 | 
 
 | 
 
 | 
| Asset retirement obligation—long-term | 
13,093,000
 | 
11,839,000
 | 
 
 | 
 
 | 
| Deferred tax liability | 
0
 | 
 
 | 
 
 | 
 
 | 
| Other non-current liabilities | 
 
 | 
2,963,000
 | 
 
 | 
 
 | 
| Long-term debt, net of current maturities | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total liabilities | 
783,074,000
 | 
706,476,000
 | 
 
 | 
 
 | 
| Stockholders’ equity: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Common stock | 
0
 | 
0
 | 
 
 | 
 
 | 
| Paid-in capital | 
1,915,598,000
 | 
1,915,598,000
 | 
 
 | 
 
 | 
| Accumulated other comprehensive loss | 
0
 | 
0
 | 
 
 | 
 
 | 
| (Accumulated deficit) retained earnings | 
706,126,000
 | 
222,464,000
 | 
 
 | 
 
 | 
| Total stockholders’ equity | 
2,621,724,000
 | 
2,138,062,000
 | 
 
 | 
 
 | 
| Total liabilities and stockholders’ equity | 
3,404,798,000
 | 
2,844,538,000
 | 
 
 | 
 
 | 
| Non-Guarantor | 
 
 | 
 
 | 
 
 | 
 
 | 
| Current assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Cash and cash equivalents | 
1,000
 | 
0
 | 
 
 | 
 
 | 
| Accounts receivable—oil and natural gas sales | 
0
 | 
0
 | 
 
 | 
 
 | 
| Accounts receivable - joint interest and other | 
0
 | 
0
 | 
 
 | 
 
 | 
| Accounts receivable - intercompany | 
0
 | 
0
 | 
 
 | 
 
 | 
| Prepaid expenses and other current assets | 
0
 | 
0
 | 
 
 | 
 
 | 
| Short-term derivative instruments - asset | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total current assets | 
1,000
 | 
 
 | 
 
 | 
 
 | 
| Property and equipment: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Oil and natural gas properties, full-cost accounting | 
0
 | 
0
 | 
 
 | 
 
 | 
| Other property and equipment | 
0
 | 
0
 | 
 
 | 
 
 | 
| Accumulated depletion, depreciation, amortization and impairment | 
0
 | 
0
 | 
 
 | 
 
 | 
| Property and equipment, net | 
0
 | 
0
 | 
 
 | 
 
 | 
| Other assets: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Equity investments and investments in subsidiaries | 
44,259,000
 | 
57,641,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
 
 | 
0
 | 
 
 | 
 
 | 
| Deferred tax asset | 
 
 | 
0
 | 
 
 | 
 
 | 
| Inventories | 
0
 | 
0
 | 
 
 | 
 
 | 
| Other assets | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total other assets | 
44,259,000
 | 
57,641,000
 | 
 
 | 
 
 | 
| Total assets | 
44,260,000
 | 
57,641,000
 | 
 
 | 
 
 | 
| Current liabilities: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Accounts payable and accrued liabilities | 
0
 | 
0
 | 
 
 | 
 
 | 
| Accounts payable - intercompany | 
130,000
 | 
127,000
 | 
 
 | 
 
 | 
| Asset retirement obligation—current | 
 
 | 
0
 | 
 
 | 
 
 | 
| Short-term derivative instruments | 
0
 | 
0
 | 
 
 | 
 
 | 
| Current maturities of long-term debt | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total current liabilities | 
130,000
 | 
127,000
 | 
 
 | 
 
 | 
| Long-term derivative instruments | 
0
 | 
0
 | 
 
 | 
 
 | 
| Asset retirement obligation—long-term | 
0
 | 
0
 | 
 
 | 
 
 | 
| Deferred tax liability | 
0
 | 
 
 | 
 
 | 
 
 | 
| Other non-current liabilities | 
 
 | 
0
 | 
 
 | 
 
 | 
| Long-term debt, net of current maturities | 
0
 | 
0
 | 
 
 | 
 
 | 
| Total liabilities | 
130,000
 | 
127,000
 | 
 
 | 
 
 | 
| Stockholders’ equity: | 
 
 | 
 
 | 
 
 | 
 
 | 
| Common stock | 
0
 | 
0
 | 
 
 | 
 
 | 
| Paid-in capital | 
261,626,000
 | 
259,307,000
 | 
 
 | 
 
 | 
| Accumulated other comprehensive loss | 
(53,783,000)
 | 
(38,593,000)
 | 
 
 | 
 
 | 
| (Accumulated deficit) retained earnings | 
(163,713,000)
 | 
(163,200,000)
 | 
 
 | 
 
 | 
| Total stockholders’ equity | 
44,130,000
 | 
57,514,000
 | 
 
 | 
 
 | 
| Total liabilities and stockholders’ equity | 
$ 44,260,000
 | 
$ 57,641,000
 | 
 
 | 
 
 |