Summary of Significant Accounting Policies (Significant Changes in Contract Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Deferred revenue
Beginning Balance	$ 4,536	$ 161	$ 300	$ 2,218
Cash receipts (Payments)	6,984	5,772	47,331	19,575
Less: Impact on Revenue	10,566	4,461	46,677	20,318
Other	0	0	0	(3)
Ending Balance	$ 954	1,472	$ 954	1,472
Payables to customers related to BTC
Beginning Balance		40,935		0
Cash receipts (Payments)		(31,781)		(141,622)
Less: Impact on Revenue		0		(144,944)
Other		0		5,832
Ending Balance		9,154		9,154
Total
Beginning Balance		41,096		2,218
Cash receipts (Payments)		(26,009)		(122,047)
Less: Impact on Revenue		4,461		(124,626)
Other		0		5,829
Ending Balance		$ 10,626		$ 10,626