Leases (Lease Operating Costs) (Details 2) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2020	Sep. 18, 2020	Dec. 31, 2019
Lease Cost [Line Items]
Operating lease cost	$ 1,044	$ 5,934	$ 8,987
Lease cost
Amortization of right-of-use assets	3	9	1,188
Interest on lease liabilities	1	3	40
Total finance lease cost	4	12	1,228
Sublease income	100	2,584	4,127
General and administrative expenses
Lease Cost [Line Items]
Operating lease cost	872	5,683	8,924
Lease operating expenses
Lease Cost [Line Items]
Operating lease cost	158	214	58
CO2 operating and discovery expenses
Lease Cost [Line Items]
Operating lease cost	$ 14	$ 37	$ 5