CONDENSED CONSOLIDATING FINANCIAL INFORMATION (Balance Sheets) (Details) - USD ($) $ in Thousands |
Mar. 31, 2019 |
Dec. 31, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Current assets: |
|
|
|
|
Cash and cash equivalents |
$ 17,996
|
$ 52,297
|
|
|
Accounts receivable - oil and natural gas sales |
144,996
|
210,200
|
|
|
Accounts receivable - joint interest and other |
24,580
|
22,497
|
|
|
Accounts receivable - intercompany |
0
|
0
|
|
|
Prepaid expenses and other current assets |
12,560
|
10,607
|
|
|
Short-term derivative instruments |
17,958
|
21,352
|
|
|
Total current assets |
218,090
|
316,953
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
10,312,124
|
10,026,836
|
|
|
Other property and equipment |
96,204
|
92,667
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(4,757,814)
|
(4,640,098)
|
|
|
Property and equipment, net |
5,650,514
|
5,479,405
|
|
|
Other assets: |
|
|
|
|
Equity investments and investments in subsidiaries |
244,119
|
236,121
|
|
|
Inventories |
11,018
|
4,754
|
|
|
Operating lease assets |
29,795
|
0
|
|
|
Operating lease assets - related parties |
58,659
|
0
|
|
|
Other assets |
13,314
|
13,803
|
|
|
Total other assets |
356,905
|
254,678
|
|
|
Total assets |
6,225,509
|
6,051,036
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
568,184
|
518,380
|
|
|
Accounts payable - intercompany |
0
|
0
|
|
|
Short-term derivative instruments |
25,921
|
20,401
|
|
|
Current portion of operating lease liabilities |
27,983
|
0
|
|
|
Current portion of operating lease liabilities - related parties |
20,618
|
0
|
|
|
Current maturities of long-term debt |
656
|
651
|
|
|
Total current liabilities |
643,362
|
539,432
|
|
|
Long-term derivative instruments |
287
|
13,992
|
|
|
Asset retirement obligation—long-term |
82,900
|
79,952
|
$ 76,267
|
|
Deferred tax liability |
3,127
|
3,127
|
|
|
Non-current operating lease liabilities |
1,812
|
0
|
|
|
Non-current operating lease liabilities - related parties |
38,041
|
0
|
|
|
Long-term debt, net of current maturities |
2,087,714
|
2,086,765
|
|
|
Total liabilities |
2,857,243
|
2,723,268
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
1,594
|
1,630
|
|
|
Paid-in capital |
4,202,023
|
4,227,532
|
|
|
Accumulated other comprehensive (loss) income |
(52,225)
|
(56,026)
|
|
|
(Accumulated deficit) retained earnings |
(783,126)
|
(845,368)
|
|
|
Total stockholders’ equity |
3,368,266
|
3,327,768
|
$ 3,088,889
|
$ 3,101,614
|
Total liabilities and stockholders’ equity |
6,225,509
|
6,051,036
|
|
|
Reportable legal entities | Parent |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
7,040
|
25,585
|
|
|
Accounts receivable - oil and natural gas sales |
93,698
|
146,075
|
|
|
Accounts receivable - joint interest and other |
12,084
|
16,212
|
|
|
Accounts receivable - intercompany |
694,036
|
671,633
|
|
|
Prepaid expenses and other current assets |
11,412
|
8,433
|
|
|
Short-term derivative instruments |
17,958
|
21,352
|
|
|
Total current assets |
836,228
|
889,290
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
7,238,631
|
7,044,550
|
|
|
Other property and equipment |
92,135
|
91,916
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(4,757,774)
|
(4,640,059)
|
|
|
Property and equipment, net |
2,572,992
|
2,496,407
|
|
|
Other assets: |
|
|
|
|
Equity investments and investments in subsidiaries |
2,963,629
|
2,856,988
|
|
|
Inventories |
9,264
|
3,620
|
|
|
Operating lease assets |
29,795
|
|
|
|
Operating lease assets - related parties |
58,659
|
|
|
|
Other assets |
12,187
|
12,624
|
|
|
Total other assets |
3,073,534
|
2,873,232
|
|
|
Total assets |
6,482,754
|
6,258,929
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
449,459
|
419,107
|
|
|
Accounts payable - intercompany |
388,879
|
320,259
|
|
|
Short-term derivative instruments |
25,921
|
20,401
|
|
|
Current portion of operating lease liabilities |
27,983
|
|
|
|
Current portion of operating lease liabilities - related parties |
20,618
|
|
|
|
Current maturities of long-term debt |
656
|
651
|
|
|
Total current liabilities |
913,516
|
760,418
|
|
|
Long-term derivative instruments |
287
|
13,992
|
|
|
Asset retirement obligation—long-term |
69,991
|
66,859
|
|
|
Deferred tax liability |
3,127
|
3,127
|
|
|
Non-current operating lease liabilities |
1,812
|
|
|
|
Non-current operating lease liabilities - related parties |
38,041
|
|
|
|
Long-term debt, net of current maturities |
2,087,714
|
2,086,765
|
|
|
Total liabilities |
3,114,488
|
2,931,161
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
1,594
|
1,630
|
|
|
Paid-in capital |
4,202,023
|
4,227,532
|
|
|
Accumulated other comprehensive (loss) income |
(52,225)
|
(56,026)
|
|
|
(Accumulated deficit) retained earnings |
(783,126)
|
(845,368)
|
|
|
Total stockholders’ equity |
3,368,266
|
3,327,768
|
|
|
Total liabilities and stockholders’ equity |
6,482,754
|
6,258,929
|
|
|
Reportable legal entities | Guarantors |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
10,955
|
26,711
|
|
|
Accounts receivable - oil and natural gas sales |
51,298
|
64,125
|
|
|
Accounts receivable - joint interest and other |
12,496
|
6,285
|
|
|
Accounts receivable - intercompany |
388,797
|
319,464
|
|
|
Prepaid expenses and other current assets |
1,148
|
2,174
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Total current assets |
464,694
|
418,759
|
|
|
Property and equipment: |
|
|
|
|
Oil and natural gas properties |
3,074,222
|
2,983,015
|
|
|
Other property and equipment |
4,069
|
751
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(40)
|
(39)
|
|
|
Property and equipment, net |
3,078,251
|
2,983,727
|
|
|
Other assets: |
|
|
|
|
Equity investments and investments in subsidiaries |
|
0
|
|
|
Inventories |
1,754
|
1,134
|
|
|
Operating lease assets |
0
|
|
|
|
Operating lease assets - related parties |
0
|
|
|
|
Other assets |
1,127
|
1,178
|
|
|
Total other assets |
2,881
|
2,312
|
|
|
Total assets |
3,545,826
|
3,404,798
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
118,725
|
99,273
|
|
|
Accounts payable - intercompany |
693,826
|
670,708
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Current portion of operating lease liabilities |
0
|
|
|
|
Current portion of operating lease liabilities - related parties |
0
|
|
|
|
Current maturities of long-term debt |
0
|
0
|
|
|
Total current liabilities |
812,551
|
769,981
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Asset retirement obligation—long-term |
12,909
|
13,093
|
|
|
Deferred tax liability |
0
|
0
|
|
|
Non-current operating lease liabilities |
0
|
|
|
|
Non-current operating lease liabilities - related parties |
0
|
|
|
|
Long-term debt, net of current maturities |
0
|
0
|
|
|
Total liabilities |
825,460
|
783,074
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
0
|
0
|
|
|
Paid-in capital |
1,915,598
|
1,915,598
|
|
|
Accumulated other comprehensive (loss) income |
0
|
0
|
|
|
(Accumulated deficit) retained earnings |
804,768
|
706,126
|
|
|
Total stockholders’ equity |
2,720,366
|
2,621,724
|
|
|
Total liabilities and stockholders’ equity |
3,545,826
|
3,404,798
|
|
|
Reportable legal entities | Non-Guarantor |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
1
|
1
|
|
|
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 |
0
|
0
|
|
|
Total current assets |
1
|
1
|
|
|
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 |
48,004
|
44,259
|
|
|
Inventories |
0
|
0
|
|
|
Operating lease assets |
0
|
|
|
|
Operating lease assets - related parties |
0
|
|
|
|
Other assets |
0
|
0
|
|
|
Total other assets |
48,004
|
44,259
|
|
|
Total assets |
48,005
|
44,260
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
0
|
0
|
|
|
Accounts payable - intercompany |
129
|
130
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Current portion of operating lease liabilities |
0
|
|
|
|
Current portion of operating lease liabilities - related parties |
0
|
|
|
|
Current maturities of long-term debt |
0
|
0
|
|
|
Total current liabilities |
129
|
130
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Asset retirement obligation—long-term |
0
|
0
|
|
|
Deferred tax liability |
0
|
0
|
|
|
Non-current operating lease liabilities |
0
|
|
|
|
Non-current operating lease liabilities - related parties |
0
|
|
|
|
Long-term debt, net of current maturities |
0
|
0
|
|
|
Total liabilities |
129
|
130
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
0
|
0
|
|
|
Paid-in capital |
262,059
|
261,626
|
|
|
Accumulated other comprehensive (loss) income |
(50,076)
|
(53,783)
|
|
|
(Accumulated deficit) retained earnings |
(164,107)
|
(163,713)
|
|
|
Total stockholders’ equity |
47,876
|
44,130
|
|
|
Total liabilities and stockholders’ equity |
48,005
|
44,260
|
|
|
Eliminations |
|
|
|
|
Current assets: |
|
|
|
|
Cash and cash equivalents |
0
|
0
|
|
|
Accounts receivable - oil and natural gas sales |
0
|
0
|
|
|
Accounts receivable - joint interest and other |
0
|
0
|
|
|
Accounts receivable - intercompany |
(1,082,833)
|
(991,097)
|
|
|
Prepaid expenses and other current assets |
0
|
0
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Total current assets |
(1,082,833)
|
(991,097)
|
|
|
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 |
(2,767,514)
|
(2,665,126)
|
|
|
Inventories |
0
|
0
|
|
|
Operating lease assets |
0
|
|
|
|
Operating lease assets - related parties |
0
|
|
|
|
Other assets |
0
|
1
|
|
|
Total other assets |
(2,767,514)
|
(2,665,125)
|
|
|
Total assets |
(3,851,076)
|
(3,656,951)
|
|
|
Current liabilities: |
|
|
|
|
Accounts payable and accrued liabilities |
0
|
0
|
|
|
Accounts payable - intercompany |
(1,082,834)
|
(991,097)
|
|
|
Short-term derivative instruments |
0
|
0
|
|
|
Current portion of operating lease liabilities |
0
|
|
|
|
Current portion of operating lease liabilities - related parties |
0
|
|
|
|
Current maturities of long-term debt |
0
|
0
|
|
|
Total current liabilities |
(1,082,834)
|
(991,097)
|
|
|
Long-term derivative instruments |
0
|
0
|
|
|
Asset retirement obligation—long-term |
0
|
0
|
|
|
Deferred tax liability |
0
|
0
|
|
|
Non-current operating lease liabilities |
0
|
|
|
|
Non-current operating lease liabilities - related parties |
0
|
|
|
|
Long-term debt, net of current maturities |
0
|
0
|
|
|
Total liabilities |
(1,082,834)
|
(991,097)
|
|
|
Stockholders’ equity: |
|
|
|
|
Common stock |
0
|
0
|
|
|
Paid-in capital |
(2,177,657)
|
(2,177,224)
|
|
|
Accumulated other comprehensive (loss) income |
50,076
|
53,783
|
|
|
(Accumulated deficit) retained earnings |
(640,661)
|
(542,413)
|
|
|
Total stockholders’ equity |
(2,768,242)
|
(2,665,854)
|
|
|
Total liabilities and stockholders’ equity |
$ (3,851,076)
|
$ (3,656,951)
|
|
|