Leases (Schedule of lease costs) (Details) - USD ($) $ in Thousands		3 Months Ended	9 Months Ended
		Sep. 30, 2019	Sep. 30, 2019
Leases [Abstract]
Amortization of finance leased assets		$ 1,005	$ 2,985
Interest on finance lease liabilities		91	302
Operating lease cost		1,267	2,914
Short-term lease cost	[1]	10,841	32,857
Variable lease cost		93	283
Total lease cost		13,297	39,341
Capitalized costs included in short-term lease costs		$ 7,000	$ 22,000

[1] Short-term lease cost includes amounts capitalized related to our oil and natural gas segment of $7.0 million and $22.0 million, respectively.