Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Contract Balances
Unbilled revenue	$ 24.3	$ 24.7
Deferred revenue	$ 1.1	$ 0.8
Products
Disaggregation of Revenue [Line Items]
Percentage of revenues	51.00%
Rental revenue
Disaggregation of Revenue [Line Items]
Percentage of revenues	25.00%
Field service and other revenue
Disaggregation of Revenue [Line Items]
Percentage of revenues	24.00%
United States
Disaggregation of Revenue [Line Items]
Percentage of revenues	99.00%