Revenue Contract Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Movement in Deferred Revenue [Roll Forward]
Contract with Customer, Liability	$ 7,099
Contract with Customer, Liability	11,800
Equipment revenue [Member]
Movement in Deferred Revenue [Roll Forward]
Increase (Decrease) in Deferred Revenue	(300)
Deferred Revenue, Additions	1,600
Software revenue [Member]
Movement in Deferred Revenue [Roll Forward]
Increase (Decrease) in Deferred Revenue	(700)
Deferred Revenue, Additions	$ 4,100