Summary of Significant Accounting Policies (Significant Changes in Contract Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Deferred revenue
Beginning Balance	$ 631	$ 300
Cash receipts (Payments)	9,067	28,658
Less: Impact on Revenue	9,333	15,643
Other	0	0
Ending Balance	365	$ 13,315
Payables to customers related to BTC
Beginning Balance	255,193
Cash receipts (Payments)	0
Less: Impact on Revenue	0
Other	0
Ending Balance	255,193
Total
Beginning Balance	255,824
Cash receipts (Payments)	9,067
Less: Impact on Revenue	9,333
Other	0
Ending Balance	$ 255,558