Fresh Start Accounting - Condensed Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 18, 2020	Dec. 31, 2019
Cash and cash equivalents		$ 73,372
Accrued production receivable		112,832
Trade and other receivables, net		36,221
Derivative assets		32,635
Other current assets		12,968
Total current assets		268,028
Proved properties		11,723,546
Unevaluated properties		650,553
CO2 properties		1,198,515
Pipelines		2,339,864
Other property and equipment	$ 97,770	201,565	$ 212,334
Less accumulated depletion, depreciation, amortization and impairment		(12,864,141)
Net property and equipment		3,249,902
Operating lease right-of-use assets		1,774
Derivative assets		501
Intangible assets, net		20,405
Other assets		81,809
Total assets		3,622,419
Accounts payable and accrued liabilities		67,789
Oil and gas production payable		39,372
Oil and gas production payable		16,705
Derivative liabilities		8,613
Total current liabilities		115,774
Long-term debt, net of current portion		140,000
Asset retirement obligations		2,727
Derivative liabilities		295
Total long-term liabilities not subject to compromise		143,022
Liabilities subject to compromise		2,823,506
Predecessor common stock		510
Predecessor paid-in capital in excess of par		2,764,915
Predecessor treasury stock, at cost		(6,202)
Successor common stock		50
Successor paid-in capital in excess of par		1,095,369
Accumulated deficit		(2,219,106)
Total stockholders' equity		540,117
Total liabilities and stockholders' equity		3,622,419
Accounts payable and accrued liabilities		102,793
Liabilities subject to compromise		2,823,506
Total assets		(1,861,589)
Long-term debt, net of current portion		(25,151)
Asset retirement obligations		(24,697)
Deferred tax liabilities, net		(414,120)
Operating lease liabilities		10
Other liabilities		18,599
Total long-term liabilities		(445,359)
Accumulated deficit		(1,420,303)
Total stockholders' equity		(1,420,303)
Total liabilities and stockholders' equity		(1,861,589)
Cash and cash equivalents		45,585
Restricted cash		10,662
Accrued production receivable		112,832
Trade and other receivables, net		36,221
Derivative assets		32,635
Other current assets		12,429
Total current assets		250,364
Proved properties		782,233
Unevaluated properties		111,983
CO2 properties		187,346
Pipelines		132,618
Other property and equipment		97,413
Less accumulated depletion, depreciation, amortization and impairment		0
Net property and equipment		1,311,593
Operating lease right-of-use assets		1,843
Derivative assets		501
Intangible assets, net		100,083
Other assets		87,023
Total assets		1,751,407
Accounts payable and accrued liabilities		174,320
Oil and gas production payable		56,077
Derivative liabilities		8,613
Current maturities of long-term debt		73,563
Operating lease liabilities		728
Total current liabilities		313,301
Long-term debt, net of current portion		157,459
Asset retirement obligations		158,438
Derivative liabilities		295
Deferred tax liabilities, net		3,831
Operating lease liabilities		525
Other liabilities		22,139
Total long-term liablities not subject to compromise		342,687
Successor common stock		50
Successor paid-in-capital in excess of par		1,095,369
Equity value		1,095,419
Total liabilities and stockholders' equity		1,751,407
Reorganization Adjustments
Cash and cash equivalents		(27,787)
Restricted cash		10,662
Other current assets		(539)
Total current assets		(17,664)
Operating lease right-of-use assets		0
Other assets		8,241
Total assets		(9,423)
Total current liabilities		193,454
Total long-term liabilities not subject to compromise		645,024
Predecessor common stock		(510)
Predecessor paid-in capital in excess of par		(2,764,915)
Predecessor treasury stock, at cost		6,202
Successor common stock		50
Successor paid-in capital in excess of par		1,095,369
Accumulated deficit		3,639,409
Total stockholders' equity		1,975,605
Total liabilities and stockholders' equity		(9,423)
Current maturities of long-term debt		73,199
Operating lease liabilities		757
Long-term debt, net of current portion		42,610
Asset retirement obligation		180,408
Deferred tax liabilities, net		417,951
Operating lease liabilities		515
Other liabilities		3,540
Liabilities subject to compromise		(2,823,506)
Fresh Start Adjustments
Trade and other receivables, net		0
Total current assets		0
Proved properties		(10,941,313)
Unevaluated properties		(538,570)
CO2 properties		(1,011,169)
Pipelines		(2,207,246)
Other property and equipment		(104,152)
Less accumulated depletion, depreciation, amortization and impairment		12,864,141
Net property and equipment		(1,938,309)
Operating lease right-of-use assets		69
Intangible assets, net		79,678
Other assets		(3,027)
Accounts payable and accrued liabilities		3,738
Current maturities of long-term debt		364
Operating lease liabilities		(29)
Total current liabilities		$ 4,073