Condensed Consolidating Financial Information (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
Current assets: |
|
|
|
|
Cash and cash equivalents |
$ 118,613
|
$ 99,557
|
|
|
Accounts receivable—oil and natural gas |
199,457
|
182,213
|
|
|
Accounts receivable - intercompany |
|
0
|
|
|
Prepaid expenses and other current assets |
7,564
|
4,912
|
|
|
Short-term derivative instruments |
50,906
|
78,847
|
|
|
Total current assets |
376,540
|
365,529
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
9,470,697
|
9,169,156
|
|
|
Other property and equipment |
89,648
|
86,754
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(4,264,647)
|
(4,153,733)
|
|
|
Property and equipment, net |
5,295,698
|
5,102,177
|
|
|
Other assets |
|
|
|
|
Equity investments and investments in subsidiaries |
311,694
|
302,112
|
|
|
Long-term derivative instruments |
15,769
|
8,685
|
|
|
Deferred tax asset |
0
|
1,208
|
|
|
Inventories |
8,505
|
8,227
|
|
|
Other assets |
20,186
|
19,814
|
|
|
Total other assets |
356,154
|
340,046
|
|
|
Total assets |
6,028,392
|
5,807,752
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
577,548
|
553,609
|
|
|
Accounts payable - intercompany |
0
|
0
|
|
|
Asset retirement obligation—current |
120
|
120
|
$ 195
|
|
Short-term derivative instruments |
37,570
|
32,534
|
|
|
Current maturities of long-term debt |
629
|
622
|
|
|
Total current liabilities |
615,867
|
586,885
|
|
|
Long-term derivative instruments |
2,499
|
2,989
|
|
|
Asset retirement obligation—long-term |
76,267
|
74,980
|
41,142
|
|
Deferred tax liability |
2,884
|
0
|
|
|
Other non-current liabilities |
2,963
|
2,963
|
|
|
Long-term debt, net of current maturities |
2,239,023
|
2,038,321
|
|
|
Total liabilities |
2,939,503
|
2,706,138
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
1,735
|
1,831
|
|
|
Paid-in capital |
4,319,034
|
4,416,250
|
|
|
Accumulated other comprehensive (loss) income |
(46,042)
|
(40,539)
|
|
|
Retained (deficit) earnings |
(1,185,838)
|
(1,275,928)
|
|
|
Total stockholders’ equity |
3,088,889
|
3,101,614
|
$ 2,801,754
|
$ 2,183,892
|
Total liabilities and stockholders’ equity |
6,028,392
|
5,807,752
|
|
|
Reportable Legal Entities | Parent |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
81,357
|
67,908
|
|
|
Accounts receivable—oil and natural gas |
133,387
|
128,121
|
|
|
Accounts receivable - intercompany |
585,111
|
554,439
|
|
|
Prepaid expenses and other current assets |
6,115
|
4,719
|
|
|
Short-term derivative instruments |
50,906
|
78,847
|
|
|
Total current assets |
856,876
|
834,034
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
6,769,164
|
6,562,147
|
|
|
Other property and equipment |
89,597
|
86,711
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(4,264,609)
|
(4,153,696)
|
|
|
Property and equipment, net |
2,594,152
|
2,495,162
|
|
|
Other assets |
|
|
|
|
Equity investments and investments in subsidiaries |
2,458,237
|
2,361,575
|
|
|
Long-term derivative instruments |
15,769
|
8,685
|
|
|
Deferred tax asset |
0
|
1,208
|
|
|
Inventories |
6,045
|
5,816
|
|
|
Other assets |
13,569
|
12,483
|
|
|
Total other assets |
2,493,620
|
2,389,767
|
|
|
Total assets |
5,944,648
|
5,718,963
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
443,963
|
416,249
|
|
|
Accounts payable - intercompany |
64,980
|
63,373
|
|
|
Asset retirement obligation—current |
120
|
120
|
|
|
Short-term derivative instruments |
37,570
|
32,534
|
|
|
Current maturities of long-term debt |
629
|
622
|
|
|
Total current liabilities |
547,262
|
512,898
|
|
|
Long-term derivative instruments |
2,499
|
2,989
|
|
|
Asset retirement obligation—long-term |
64,091
|
63,141
|
|
|
Deferred tax liability |
2,884
|
|
|
|
Other non-current liabilities |
0
|
0
|
|
|
Long-term debt, net of current maturities |
2,239,023
|
2,038,321
|
|
|
Total liabilities |
2,855,759
|
2,617,349
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
1,735
|
1,831
|
|
|
Paid-in capital |
4,319,034
|
4,416,250
|
|
|
Accumulated other comprehensive (loss) income |
(46,042)
|
(40,539)
|
|
|
Retained (deficit) earnings |
(1,185,838)
|
(1,275,928)
|
|
|
Total stockholders’ equity |
3,088,889
|
3,101,614
|
|
|
Total liabilities and stockholders’ equity |
5,944,648
|
5,718,963
|
|
|
Reportable Legal Entities | Guarantors |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
37,254
|
31,649
|
|
|
Accounts receivable—oil and natural gas |
66,070
|
54,092
|
|
|
Accounts receivable - intercompany |
64,492
|
63,374
|
|
|
Prepaid expenses and other current assets |
1,449
|
193
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Total current assets |
169,265
|
149,308
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
2,702,262
|
2,607,738
|
|
|
Other property and equipment |
51
|
43
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(38)
|
(37)
|
|
|
Property and equipment, net |
2,702,275
|
2,607,744
|
|
|
Other assets |
|
|
|
|
Equity investments and investments in subsidiaries |
77,350
|
77,744
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Deferred tax asset |
0
|
0
|
|
|
Inventories |
2,460
|
2,411
|
|
|
Other assets |
6,617
|
7,331
|
|
|
Total other assets |
86,427
|
87,486
|
|
|
Total assets |
2,957,967
|
2,844,538
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
133,585
|
137,361
|
|
|
Accounts payable - intercompany |
584,495
|
554,313
|
|
|
Asset retirement obligation—current |
0
|
0
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Current maturities of long-term debt |
0
|
0
|
|
|
Total current liabilities |
718,080
|
691,674
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Asset retirement obligation—long-term |
12,176
|
11,839
|
|
|
Deferred tax liability |
0
|
|
|
|
Other non-current liabilities |
2,963
|
2,963
|
|
|
Long-term debt, net of current maturities |
0
|
0
|
|
|
Total liabilities |
733,219
|
706,476
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
0
|
0
|
|
|
Paid-in capital |
1,915,598
|
1,915,598
|
|
|
Accumulated other comprehensive (loss) income |
0
|
0
|
|
|
Retained (deficit) earnings |
309,150
|
222,464
|
|
|
Total stockholders’ equity |
2,224,748
|
2,138,062
|
|
|
Total liabilities and stockholders’ equity |
2,957,967
|
2,844,538
|
|
|
Reportable Legal Entities | Non-Guarantor |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
2
|
0
|
|
|
Accounts receivable—oil and natural gas |
0
|
0
|
|
|
Accounts receivable - intercompany |
0
|
0
|
|
|
Prepaid expenses and other current assets |
0
|
0
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Total current assets |
2
|
0
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
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 |
53,563
|
57,641
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Deferred tax asset |
0
|
0
|
|
|
Inventories |
0
|
0
|
|
|
Other assets |
0
|
0
|
|
|
Total other assets |
53,563
|
57,641
|
|
|
Total assets |
53,565
|
57,641
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
0
|
0
|
|
|
Accounts payable - intercompany |
128
|
127
|
|
|
Asset retirement obligation—current |
0
|
0
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Current maturities of long-term debt |
0
|
0
|
|
|
Total current liabilities |
128
|
127
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Asset retirement obligation—long-term |
0
|
0
|
|
|
Deferred tax liability |
0
|
|
|
|
Other non-current liabilities |
0
|
0
|
|
|
Long-term debt, net of current maturities |
0
|
0
|
|
|
Total liabilities |
128
|
127
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
0
|
0
|
|
|
Paid-in capital |
260,877
|
259,307
|
|
|
Accumulated other comprehensive (loss) income |
(43,909)
|
(38,593)
|
|
|
Retained (deficit) earnings |
(163,531)
|
(163,200)
|
|
|
Total stockholders’ equity |
53,437
|
57,514
|
|
|
Total liabilities and stockholders’ equity |
53,565
|
57,641
|
|
|
Eliminations |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
0
|
0
|
|
|
Accounts receivable—oil and natural gas |
0
|
0
|
|
|
Accounts receivable - intercompany |
(649,603)
|
(617,813)
|
|
|
Prepaid expenses and other current assets |
0
|
0
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Total current assets |
(649,603)
|
(617,813)
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
(729)
|
(729)
|
|
|
Other property and equipment |
0
|
0
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
0
|
0
|
|
|
Property and equipment, net |
(729)
|
(729)
|
|
|
Other assets |
|
|
|
|
Equity investments and investments in subsidiaries |
(2,277,456)
|
(2,194,848)
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Deferred tax asset |
0
|
0
|
|
|
Inventories |
0
|
0
|
|
|
Other assets |
0
|
0
|
|
|
Total other assets |
(2,277,456)
|
(2,194,848)
|
|
|
Total assets |
(2,927,788)
|
(2,813,390)
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
0
|
(1)
|
|
|
Accounts payable - intercompany |
(649,603)
|
(617,813)
|
|
|
Asset retirement obligation—current |
0
|
0
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Current maturities of long-term debt |
0
|
0
|
|
|
Total current liabilities |
(649,603)
|
(617,814)
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Asset retirement obligation—long-term |
0
|
0
|
|
|
Deferred tax liability |
0
|
|
|
|
Other non-current liabilities |
0
|
0
|
|
|
Long-term debt, net of current maturities |
0
|
0
|
|
|
Total liabilities |
(649,603)
|
(617,814)
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
0
|
0
|
|
|
Paid-in capital |
(2,176,475)
|
(2,174,905)
|
|
|
Accumulated other comprehensive (loss) income |
43,909
|
38,593
|
|
|
Retained (deficit) earnings |
(145,619)
|
(59,264)
|
|
|
Total stockholders’ equity |
(2,278,185)
|
(2,195,576)
|
|
|
Total liabilities and stockholders’ equity |
$ (2,927,788)
|
$ (2,813,390)
|
|
|