Leases (Schedule of lease costs) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Leases [Abstract]
Amortization of finance leased assets	$ 4,001
Interest on finance lease liabilities	382
Operating lease cost	4,034
Short-term lease cost	38,868	[1]
Variable lease cost	351
Total lease cost	$ 47,636

[1] Short-term lease cost includes amounts capitalized related to our oil and natural gas segment of $25.1 million.