Deferred revenue and remaining performance obligations - Performance Obligation (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01 $ in Millions	Jun. 30, 2020 USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation, amount	$ 69.2
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation, remaining duration (in years)	6 months
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation, remaining duration (in years)	6 years 6 months