Organization and Accounting Policies (Rollforward of Aggregate Allowance for Bad Debt) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Organization and Accounting Policies [Abstract]
Balance at beginning of period	$ (5,575)	$ (1,904)	$ (2,273)	$ (1,508)
Bad debt charge	(318)	(151)	(814)	(1,140)
Adjustment associated with reversal of allowance on Mutamba receivable				593
Adjustment associated with Sasol acquisition			(2,879)
Foreign currency gain (loss)	117		190
Balance at end of period	$ (5,776)	$ (2,055)	$ (5,776)	$ (2,055)