Leases (Schedule of lease costs) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases [Abstract]
Amortization of finance leased assets		$ 181	$ 1,036	$ 1,248	$ 2,061
Interest on finance lease liabilities		4	60	33	130
Operating lease cost		984	1,395	2,011	2,640
Short-term lease cost	[1]	3,179	2,751	5,771	6,742
Variable lease cost		0	83	0	165
Total lease cost		4,348	5,325	9,063	11,737
Capitalized costs included in short-term lease costs		$ 100	$ 400	$ 200	$ 1,400

[1] Short-term lease cost includes amounts capitalized related to our oil and natural gas segment of $0.1 million, $0.4 million, $0.2 million, and $1.4 million for the three and six months ended June 30, 2021 and June 30, 2020, respectively