CONDENSED CONSOLIDATING FINANCIAL INFORMATION (Balance Sheets) (Details) - USD ($) $ in Thousands |
Jun. 30, 2019 |
Mar. 31, 2019 |
Dec. 31, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Current assets: |
|
|
|
|
|
|
Cash and cash equivalents |
$ 20,777
|
|
$ 52,297
|
|
|
|
Accounts receivable - oil and natural gas sales |
131,675
|
|
210,200
|
|
|
|
Accounts receivable - joint interest and other |
46,645
|
|
22,497
|
|
|
|
Accounts receivable - intercompany |
0
|
|
0
|
|
|
|
Prepaid expenses and other current assets |
9,474
|
|
10,607
|
|
|
|
Short-term derivative instruments |
134,920
|
|
21,352
|
|
|
|
Total current assets |
343,491
|
|
316,953
|
|
|
|
Property and equipment: |
|
|
|
|
|
|
Oil and natural gas properties |
10,510,427
|
|
10,026,836
|
|
|
|
Other property and equipment |
96,413
|
|
92,667
|
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(4,882,729)
|
|
(4,640,098)
|
|
|
|
Property and equipment, net |
5,724,111
|
|
5,479,405
|
|
|
|
Other assets: |
|
|
|
|
|
|
Equity investments and investments in subsidiaries |
119,307
|
|
236,121
|
|
|
|
Long-term derivative instruments |
5,036
|
|
0
|
|
|
|
Deferred tax asset |
179,331
|
|
0
|
|
|
|
Inventories |
9,001
|
|
4,754
|
|
|
|
Operating lease assets |
19,334
|
|
|
|
|
|
Operating lease assets - related parties |
53,579
|
|
|
|
|
|
Other assets |
12,280
|
|
13,803
|
|
|
|
Total other assets |
397,868
|
|
254,678
|
|
|
|
Total assets |
6,465,470
|
|
6,051,036
|
|
|
|
Current liabilities: |
|
|
|
|
|
|
Accounts payable and accrued liabilities |
493,830
|
|
518,380
|
|
|
|
Accounts payable - intercompany |
0
|
|
0
|
|
|
|
Short-term derivative instruments |
198
|
|
20,401
|
|
|
|
Current portion of operating lease liabilities |
17,999
|
|
|
|
|
|
Current portion of operating lease liabilities - related parties |
20,817
|
|
|
|
|
|
Current maturities of long-term debt |
615
|
|
651
|
|
|
|
Total current liabilities |
533,459
|
|
539,432
|
|
|
|
Long-term derivative instruments |
210
|
|
13,992
|
|
|
|
Asset retirement obligation—long-term |
88,491
|
|
79,952
|
$ 76,815
|
|
|
Deferred tax liability |
3,127
|
|
3,127
|
|
|
|
Non-current operating lease liabilities |
1,335
|
|
|
|
|
|
Non-current operating lease liabilities - related parties |
32,762
|
|
|
|
|
|
Long-term debt, net of current maturities |
2,198,678
|
|
2,086,765
|
|
|
|
Total liabilities |
2,858,062
|
|
2,723,268
|
|
|
|
Stockholders’ equity: |
|
|
|
|
|
|
Common stock |
1,594
|
|
1,630
|
|
|
|
Paid-in capital |
4,202,599
|
|
4,227,532
|
|
|
|
Accumulated other comprehensive loss |
(48,615)
|
|
(56,026)
|
|
|
|
(Accumulated deficit) retained earnings |
(548,170)
|
|
(845,368)
|
|
|
|
Total stockholders’ equity |
3,607,408
|
$ 3,368,266
|
3,327,768
|
$ 3,195,199
|
$ 3,088,889
|
$ 3,101,614
|
Total liabilities and stockholders’ equity |
6,465,470
|
|
6,051,036
|
|
|
|
Reportable legal entities | Parent |
|
|
|
|
|
|
Current assets: |
|
|
|
|
|
|
Cash and cash equivalents |
10,940
|
|
25,585
|
|
|
|
Accounts receivable - oil and natural gas sales |
4,116
|
|
146,075
|
|
|
|
Accounts receivable - joint interest and other |
9,043
|
|
16,212
|
|
|
|
Accounts receivable - intercompany |
819,584
|
|
671,633
|
|
|
|
Prepaid expenses and other current assets |
5,948
|
|
8,433
|
|
|
|
Short-term derivative instruments |
134,920
|
|
21,352
|
|
|
|
Total current assets |
984,551
|
|
889,290
|
|
|
|
Property and equipment: |
|
|
|
|
|
|
Oil and natural gas properties |
1,352,894
|
|
7,044,550
|
|
|
|
Other property and equipment |
92,343
|
|
91,916
|
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(1,414,011)
|
|
(4,640,059)
|
|
|
|
Property and equipment, net |
31,226
|
|
2,496,407
|
|
|
|
Other assets: |
|
|
|
|
|
|
Equity investments and investments in subsidiaries |
5,171,925
|
|
2,856,988
|
|
|
|
Long-term derivative instruments |
5,036
|
|
|
|
|
|
Deferred tax asset |
179,331
|
|
|
|
|
|
Inventories |
188
|
|
3,620
|
|
|
|
Operating lease assets |
19,334
|
|
|
|
|
|
Operating lease assets - related parties |
53,579
|
|
|
|
|
|
Other assets |
11,682
|
|
12,624
|
|
|
|
Total other assets |
5,441,075
|
|
2,873,232
|
|
|
|
Total assets |
6,456,852
|
|
6,258,929
|
|
|
|
Current liabilities: |
|
|
|
|
|
|
Accounts payable and accrued liabilities |
74,597
|
|
419,107
|
|
|
|
Accounts payable - intercompany |
469,071
|
|
320,259
|
|
|
|
Short-term derivative instruments |
198
|
|
20,401
|
|
|
|
Current portion of operating lease liabilities |
17,999
|
|
|
|
|
|
Current portion of operating lease liabilities - related parties |
20,817
|
|
|
|
|
|
Current maturities of long-term debt |
615
|
|
651
|
|
|
|
Total current liabilities |
583,297
|
|
760,418
|
|
|
|
Long-term derivative instruments |
210
|
|
13,992
|
|
|
|
Asset retirement obligation—long-term |
30,035
|
|
66,859
|
|
|
|
Deferred tax liability |
3,127
|
|
3,127
|
|
|
|
Non-current operating lease liabilities |
1,335
|
|
|
|
|
|
Non-current operating lease liabilities - related parties |
32,762
|
|
|
|
|
|
Long-term debt, net of current maturities |
2,198,678
|
|
2,086,765
|
|
|
|
Total liabilities |
2,849,444
|
|
2,931,161
|
|
|
|
Stockholders’ equity: |
|
|
|
|
|
|
Common stock |
1,594
|
|
1,630
|
|
|
|
Paid-in capital |
4,202,599
|
|
4,227,532
|
|
|
|
Accumulated other comprehensive loss |
(48,615)
|
|
(56,026)
|
|
|
|
(Accumulated deficit) retained earnings |
(548,170)
|
|
(845,368)
|
|
|
|
Total stockholders’ equity |
3,607,408
|
|
3,327,768
|
|
|
|
Total liabilities and stockholders’ equity |
6,456,852
|
|
6,258,929
|
|
|
|
Reportable legal entities | Guarantors |
|
|
|
|
|
|
Current assets: |
|
|
|
|
|
|
Cash and cash equivalents |
9,799
|
|
26,711
|
|
|
|
Accounts receivable - oil and natural gas sales |
127,559
|
|
64,125
|
|
|
|
Accounts receivable - joint interest and other |
37,602
|
|
6,285
|
|
|
|
Accounts receivable - intercompany |
433,776
|
|
319,464
|
|
|
|
Prepaid expenses and other current assets |
3,451
|
|
2,174
|
|
|
|
Short-term derivative instruments |
0
|
|
0
|
|
|
|
Total current assets |
612,187
|
|
418,759
|
|
|
|
Property and equipment: |
|
|
|
|
|
|
Oil and natural gas properties |
9,158,193
|
|
2,983,015
|
|
|
|
Other property and equipment |
751
|
|
751
|
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(3,468,663)
|
|
(39)
|
|
|
|
Property and equipment, net |
5,690,281
|
|
2,983,727
|
|
|
|
Other assets: |
|
|
|
|
|
|
Equity investments and investments in subsidiaries |
|
|
0
|
|
|
|
Long-term derivative instruments |
0
|
|
|
|
|
|
Deferred tax asset |
0
|
|
|
|
|
|
Inventories |
8,813
|
|
1,134
|
|
|
|
Operating lease assets |
0
|
|
|
|
|
|
Operating lease assets - related parties |
0
|
|
|
|
|
|
Other assets |
598
|
|
1,178
|
|
|
|
Total other assets |
9,411
|
|
2,312
|
|
|
|
Total assets |
6,311,879
|
|
3,404,798
|
|
|
|
Current liabilities: |
|
|
|
|
|
|
Accounts payable and accrued liabilities |
419,190
|
|
99,273
|
|
|
|
Accounts payable - intercompany |
780,600
|
|
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 |
1,199,790
|
|
769,981
|
|
|
|
Long-term derivative instruments |
0
|
|
0
|
|
|
|
Asset retirement obligation—long-term |
58,456
|
|
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 |
1,258,246
|
|
783,074
|
|
|
|
Stockholders’ equity: |
|
|
|
|
|
|
Common stock |
0
|
|
0
|
|
|
|
Paid-in capital |
4,170,574
|
|
1,915,598
|
|
|
|
Accumulated other comprehensive loss |
0
|
|
0
|
|
|
|
(Accumulated deficit) retained earnings |
883,059
|
|
706,126
|
|
|
|
Total stockholders’ equity |
5,053,633
|
|
2,621,724
|
|
|
|
Total liabilities and stockholders’ equity |
6,311,879
|
|
3,404,798
|
|
|
|
Reportable legal entities | Non-Guarantors |
|
|
|
|
|
|
Current assets: |
|
|
|
|
|
|
Cash and cash equivalents |
38
|
|
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 |
75
|
|
0
|
|
|
|
Short-term derivative instruments |
0
|
|
0
|
|
|
|
Total current assets |
113
|
|
1
|
|
|
|
Property and equipment: |
|
|
|
|
|
|
Oil and natural gas properties |
69
|
|
0
|
|
|
|
Other property and equipment |
3,319
|
|
0
|
|
|
|
Accumulated depletion, depreciation, amortization and impairment |
(55)
|
|
0
|
|
|
|
Property and equipment, net |
3,333
|
|
0
|
|
|
|
Other assets: |
|
|
|
|
|
|
Equity investments and investments in subsidiaries |
51,607
|
|
44,259
|
|
|
|
Long-term derivative instruments |
0
|
|
|
|
|
|
Deferred tax asset |
0
|
|
|
|
|
|
Inventories |
0
|
|
0
|
|
|
|
Operating lease assets |
0
|
|
|
|
|
|
Operating lease assets - related parties |
0
|
|
|
|
|
|
Other assets |
0
|
|
0
|
|
|
|
Total other assets |
51,607
|
|
44,259
|
|
|
|
Total assets |
55,053
|
|
44,260
|
|
|
|
Current liabilities: |
|
|
|
|
|
|
Accounts payable and accrued liabilities |
43
|
|
0
|
|
|
|
Accounts payable - intercompany |
3,689
|
|
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 |
3,732
|
|
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 |
3,732
|
|
130
|
|
|
|
Stockholders’ equity: |
|
|
|
|
|
|
Common stock |
0
|
|
0
|
|
|
|
Paid-in capital |
262,059
|
|
261,626
|
|
|
|
Accumulated other comprehensive loss |
(46,527)
|
|
(53,783)
|
|
|
|
(Accumulated deficit) retained earnings |
(164,211)
|
|
(163,713)
|
|
|
|
Total stockholders’ equity |
51,321
|
|
44,130
|
|
|
|
Total liabilities and stockholders’ equity |
55,053
|
|
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 |
(1,253,360)
|
|
(991,097)
|
|
|
|
Prepaid expenses and other current assets |
0
|
|
0
|
|
|
|
Short-term derivative instruments |
0
|
|
0
|
|
|
|
Total current assets |
(1,253,360)
|
|
(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 |
(5,104,225)
|
|
(2,665,126)
|
|
|
|
Long-term derivative instruments |
0
|
|
|
|
|
|
Deferred tax asset |
0
|
|
|
|
|
|
Inventories |
0
|
|
0
|
|
|
|
Operating lease assets |
0
|
|
|
|
|
|
Operating lease assets - related parties |
0
|
|
|
|
|
|
Other assets |
0
|
|
1
|
|
|
|
Total other assets |
(5,104,225)
|
|
(2,665,125)
|
|
|
|
Total assets |
(6,358,314)
|
|
(3,656,951)
|
|
|
|
Current liabilities: |
|
|
|
|
|
|
Accounts payable and accrued liabilities |
0
|
|
0
|
|
|
|
Accounts payable - intercompany |
(1,253,360)
|
|
(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 |
(1,253,360)
|
|
(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 |
(1,253,360)
|
|
(991,097)
|
|
|
|
Stockholders’ equity: |
|
|
|
|
|
|
Common stock |
0
|
|
0
|
|
|
|
Paid-in capital |
(4,432,633)
|
|
(2,177,224)
|
|
|
|
Accumulated other comprehensive loss |
46,527
|
|
53,783
|
|
|
|
(Accumulated deficit) retained earnings |
(718,848)
|
|
(542,413)
|
|
|
|
Total stockholders’ equity |
(5,104,954)
|
|
(2,665,854)
|
|
|
|
Total liabilities and stockholders’ equity |
$ (6,358,314)
|
|
$ (3,656,951)
|
|
|
|