Summary of Significant Accounting Policies (Significant Changes in Contract Liabilities) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Deferred revenue
Beginning Balance	$ 13,315	$ 1,740	$ 300	$ 2,218
Cash receipts (Payments)	11,690	3,296	40,347	13,803
Less: Impact on Revenue	20,469	4,872	36,111	15,857
Other	0	(3)	0	(3)
Ending Balance	$ 4,536	161	$ 4,536	161
Payables to customers related to BTC
Beginning Balance		150,776		0
Cash receipts (Payments)		(109,841)		(109,841)
Less: Impact on Revenue		0		(144,944)
Other		0		5,832
Ending Balance		40,935		40,935
Total
Beginning Balance		152,516		2,218
Cash receipts (Payments)		(106,545)		(96,038)
Less: Impact on Revenue		4,872		(129,087)
Other		(3)		5,829
Ending Balance		$ 41,096		$ 41,096