Revenue Contract Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Movement in Deferred Revenue [Roll Forward]
Contract with Customer, Liability	$ (4,282)	$ (7,066)
Contract with Customer, Liability	(5,892)	(7,988)
Equipment revenue [Member]
Movement in Deferred Revenue [Roll Forward]
Deferred Revenue, Additions	(3,860)	(2,733)
Increase (Decrease) in Deferred Revenue	2,669	1,971
Software revenue [Member]
Movement in Deferred Revenue [Roll Forward]
Deferred Revenue, Additions	(2,366)	(4,845)
Increase (Decrease) in Deferred Revenue	$ 1,947	$ 4,685