Accounting policies - Performance obligations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Jun. 30, 2023
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Amount recognized revenue included in the contract liability balance	$ 7.2
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		$ 45.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period		9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		$ 67.3
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period		1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-12-31
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		$ 21.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period		2 years