Leases (Schedule of lease costs) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Leases [Abstract]
Amortization of finance leased assets		$ 1,025	$ 985
Interest on finance lease liabilities		70	111
Operating lease cost		1,244	598
Short-term lease cost	[1]	3,991	9,974
Variable lease cost		82	106
Total lease cost		6,412	11,774
Capitalized costs included in short-term lease costs		$ 1,000	$ 5,700

[1] Short-term lease cost includes amounts capitalized related to our oil and natural gas segment of $1.0 million and $5.7 million for the first three months of 2020 and 2019, respectively.