Leases (Schedule of lease costs) (Details) - USD ($) $ in Thousands	1 Months Ended	2 Months Ended	3 Months Ended	8 Months Ended	9 Months Ended
	Sep. 30, 2020	Aug. 31, 2020	Sep. 30, 2019	Aug. 31, 2020	Sep. 30, 2019
Leases [Abstract]
Amortization of finance leased assets	$ 350	$ 696	$ 1,005	$ 2,757	$ 2,985
Interest on finance lease liabilities	15	35	91	165	302
Operating lease cost	328	965	1,267	3,604	2,915
Short-term lease cost	867	1,448	10,841	8,190	32,857
Variable lease cost	29	58	93	223	283
Total lease cost	$ 1,589	3,202	13,297	14,939	39,341
Capitalized costs included in short-term lease costs		$ 100	$ 7,000	$ 1,500	$ 21,700