Leases (Lease Operating Costs) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Lease Cost [Line Items]
Operating lease cost	$ 8,987
Lease cost
Amortization of right-of-use assets	1,188
Interest on lease liabilities	40
Total finance lease cost	1,228
Sublease income	4,127
General and administrative expenses
Lease Cost [Line Items]
Operating lease cost	8,924
Lease operating expenses
Lease Cost [Line Items]
Operating lease cost	58
CO2 discovery and operating expenses
Lease Cost [Line Items]
Operating lease cost	$ 5