Summary of Significant Accounting Policies (Significant Changes in Contract Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Deferred revenue
Beginning Balance	$ 1,117	$ 2	$ 946	$ 631
Cash receipts (Payments)	2,706	4,371	20,633	18,107
Less: Impact on Revenue	3,573	4,366	21,329	18,731
Other	0	0	0	0
Ending Balance	250	7	250	7
Payables to customers related to BTC
Beginning Balance	699	75,330	914	255,193
Cash receipts (Payments)	0	(31,818)	(215)	(214,637)
Less: Impact on Revenue	0	0	0	0
Other	0	0	0	2,956
Ending Balance	699	43,512	699	43,512
Total
Beginning Balance	1,816	75,332	1,860	255,824
Cash receipts (Payments)	2,706	(27,447)	20,418	(196,530)
Less: Impact on Revenue	3,573	4,366	21,329	18,731
Other	0	0	0	2,956
Ending Balance	$ 949	$ 43,519	$ 949	$ 43,519