Accounting pronouncements, Remaining Performance Obligations (Details) $ in Millions	Sep. 30, 2018 USD ($)
Remaining performance obligations [Abstract]
Remaining performance obligations	$ 6.0
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Remaining performance obligations [Abstract]
Remaining performance obligations	$ 5.5
Expected timing of satisfaction, period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Remaining performance obligations [Abstract]
Remaining performance obligations	$ 0.4
Expected timing of satisfaction, period	24 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Remaining performance obligations [Abstract]
Remaining performance obligations
Expected timing of satisfaction, period	36 months