Summary of Significant Accounting Policies (Significant Changes in Contract Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Deferred revenue
Beginning Balance	$ 2	$ 4,536	$ 631	$ 300
Cash receipts (Payments)	4,371	6,984	18,107	47,331
Less: Impact on Revenue	4,366	10,566	18,731	46,677
Other	0	0	0	0
Ending Balance	7	$ 954	7	$ 954
Payables to customers related to BTC
Beginning Balance	75,330		255,193
Cash receipts (Payments)	(31,818)		(214,637)
Less: Impact on Revenue	0		0
Other	0		2,956
Ending Balance	43,512		43,512
Total
Beginning Balance	75,332		255,824
Cash receipts (Payments)	(27,447)		(196,530)
Less: Impact on Revenue	4,366		18,731
Other	0		2,956
Ending Balance	$ 43,519		$ 43,519