Leases (Lease Operating Costs) (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 18, 2020	Sep. 30, 2019	Sep. 18, 2020	Sep. 30, 2019
Operating lease cost	$ 29	$ 1,847	$ 1,187	$ 5,934	$ 6,014
Finance lease cost
Amortization of right-of-use assets	1	5	54	9	1,188
Interest on lease liabilities	0	2	2	3	40
Total finance lease cost	1	7	56	12	1,228
Sublease income	100	790	964	2,584	3,331
General and administrative expenses
Operating lease cost	8	1,715	1,187	5,683	6,014
Lease operating expenses
Operating lease cost	19	121	0	214	0
CO2 operating and discovery expenses
Operating lease cost	$ 2	$ 11	$ 0	$ 37	$ 0

Amount of interest expense on finance lease liability.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Section 50
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of amortization expense attributable to right-of-use asset from finance lease.

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Amount of lease cost recognized by lessee for lease contract.

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Amount of single lease cost, calculated by allocation of remaining cost of lease over remaining lease term. Includes, but is not limited to, single lease cost, after impairment of right-of-use asset, calculated by amortization of remaining right-of-use asset and accretion of lease liability.

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Amount of sublease income excluding finance and operating lease expense.

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