Fresh Start Accounting (Condensed Consolidated Balance Sheet) (Details 3) - USD ($)	Dec. 31, 2020	Sep. 18, 2020	Dec. 31, 2019
Fresh-Start Adjustment [Line Items]
Cash and cash equivalents		$ 73,372,000
Accrued production receivable		112,832,000
Trade and other receivables		36,221,000
Derivative assets		32,635,000
Other current assets		12,968,000
Total current assets		268,028,000
Proved properties		11,723,546,000
Unevaluated properties		650,553,000
CO2 properties		1,198,515,000
Pipelines		2,339,864,000
Other property and equipment	$ 86,610,000	201,565,000	$ 212,334,000
Less accumulated depletion, depreciation, amortization and impairment		(12,864,141,000)
Net property and equipment		3,249,902,000
Operating lease right-of-use assets		1,774,000
Derivative assets		501,000
Intangible assets, net		20,405,000
Other assets		81,809,000
Total assets		3,622,419,000
Accounts payable and accrued liabilities		67,789,000
Oil and gas production payable		39,372,000
Oil and gas production payable		16,705,000
Derivative liabilities		8,613,000
Total current liabilities		115,774,000
Long-term debt, net of current portion		140,000,000
Asset retirement obligations		2,727,000
Derivative liabilities		295,000
Total long-term liabilities not subject to compromise		143,022,000
Liabilities subject to compromise		2,823,506,000
Predecessor common stock		510,000
Predecessor paid-in capital in excess of par		2,764,915,000
Predecessor treasury stock, at cost		(6,202,000)
Successor common stock		50,000
Successor paid-in capital in excess of par		1,095,369,000
Accumulated deficit		(2,219,106,000)
Total stockholders' equity		540,117,000
Total liabilities and stockholders' equity		3,622,419,000
Accounts payable and accrued liabilities		102,793,000
Current maturities of long-term debt		73,199,000
Operating lease liabilities		757,000
Long-term debt, net of current portion		42,610,000
Asset retirement obligations		180,408,000
Operating lease liabilities		515,000
Other liabilities		3,540,000
Liabilities subject to compromise		2,823,506,000
Deferred tax liabilities, net		414,100,000
Cash and cash equivalents		45,585,000
Restricted cash		10,662,000
Accrued production receivable		112,832,000
Trade and other receivables, net		36,221,000
Derivative assets		32,635,000
Other current assets		12,429,000
Total current assets		250,364,000
Proved properties		782,233,000
Unevaluated properties		111,983,000
CO2 properties		187,346,000
Pipelines		132,618,000
Other property and equipment		97,413,000
Less accumulated depletion, depreciation, amortization and impairment		0
Net property and equipment		1,311,593,000
Operating lease right-of-use assets		1,843,000
Derivative assets		501,000
Intangible assets, net		100,083,000
Other assets		87,023,000
Total assets		1,751,407,000
Accounts payable and accrued liabilities		174,320,000
Oil and gas production payable		56,077,000
Derivative liabilities		8,613,000
Current maturities of long-term debt		73,563,000
Operating lease liabilities		728,000
Total current liabilities		313,301,000
Long-term debt, net of current portion		157,459,000
Asset retirement obligations		158,438,000
Derivative liabilities		295,000
Deferred tax liabilities, net		3,831,000
Operating lease liabilities		525,000
Other liabilities		22,139,000
Total long-term liabilities not subject to compromise		342,687,000
Successor common stock		50,000
Successor paid-in capital in excess of par		1,095,369,000
Equity value		1,095,419,000
Total liabilities and stockholders' equity		1,751,407,000
Reorganization Adjustments
Fresh-Start Adjustment [Line Items]
Cash and cash equivalents		(27,787,000)
Restricted cash		10,662,000
Other current assets		(539,000)
Total current assets		(17,664,000)
Other assets		8,241,000
Total assets		(9,423,000)
Oil and gas production payable		16,705,000
Total current liabilities		193,454,000
Total long-term liabilities not subject to compromise		645,024,000
Predecessor common stock		(510,000)
Predecessor paid-in capital in excess of par		(2,764,915,000)
Predecessor treasury stock, at cost		6,202,000
Successor common stock		50,000
Successor paid-in capital in excess of par		1,095,369,000
Accumulated deficit		3,639,409,000
Total stockholders' equity		1,975,605,000
Total liabilities and stockholders' equity		(9,423,000)
Current maturities of long-term debt		73,199,000
Operating lease liabilities		757,000
Long-term debt, net of current portion		42,610,000
Asset retirement obligations		180,408,000
Deferred tax liabilities, net		417,951,000
Operating lease liabilities		515,000
Other liabilities		3,540,000
Liabilities subject to compromise		(2,823,506,000)
Fresh Start Adjustments
Fresh-Start Adjustment [Line Items]
Proved properties		(10,941,313,000)
Unevaluated properties		(538,570,000)
CO2 properties		(1,011,169,000)
Pipelines		(2,207,246,000)
Other property and equipment		(104,152,000)
Less accumulated depletion, depreciation, amortization and impairment		12,864,141,000
Net property and equipment		(1,938,309,000)
Operating lease right-of-use assets		69,000
Intangible assets, net		79,678,000
Other assets		(3,027,000)
Total assets		(1,861,589,000)
Accounts payable and accrued liabilities		3,738,000
Current maturities of long-term debt		364,000
Operating lease liabilities		(29,000)
Total current liabilities		4,073,000
Long-term debt, net of current portion		(25,151,000)
Asset retirement obligations		(24,697,000)
Deferred tax liabilities, net		(414,120,000)
Operating lease liabilities		10,000
Other liabilities		18,599,000
Total long-term liabilities not subject to compromise		(445,359,000)
Accumulated deficit		(1,420,303,000)
Total stockholders' equity		(1,420,303,000)
Total liabilities and stockholders' equity		$ (1,861,589,000)