Income taxes - Tax Credit Carryforwards (Details) $ in Millions	Dec. 31, 2022 USD ($)
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, set to expire	$ 141.9
2023
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, set to expire	27.0
2024
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, set to expire	22.5
2025
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, set to expire	20.7
2026
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, set to expire	33.7
2027
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, set to expire	9.5
Thereafter
Tax Credit Carryforward [Line Items]
Tax credit carryforwards, set to expire	$ 28.5