Leases (Schedule of lease costs) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Amortization of finance leased assets		$ 1,067	$ 1,025
Interest on finance lease liabilities		29	70
Operating lease cost		1,047	1,244
Short-term lease cost	[1]	1,444	3,991
Variable lease cost		58	82
Total lease cost		3,645	6,412
Capitalized costs included in short-term lease costs		$ 100	$ 1,000

[1] Short-term lease cost includes amounts capitalized related to our oil and natural gas segment of $0.1 million and $1.0 million for the first three months of 2021 and 2020, respectively