Revenue Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Movement in Deferred Revenue [Roll Forward]
Contract with Customer, Liability	$ (4,282)	$ (7,066)
Contract with Customer, Liability	(6,425)	(11,761)
Equipment revenue [Member]
Movement in Deferred Revenue [Roll Forward]
Deferred Revenue, Additions	(1,343)	(1,558)
Increase (Decrease) in Deferred Revenue	448	288
Software revenue [Member]
Movement in Deferred Revenue [Roll Forward]
Deferred Revenue, Additions	(1,593)	(4,080)
Increase (Decrease) in Deferred Revenue	$ 345	$ 655