Income taxes - Tax Loss Carryforwards (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
U.S. Federal	$ 370.7
State and local	203.4
Foreign	266.3
Total tax loss carryforwards	840.4	$ 795.2
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, not set to expire	272.5
Total tax loss carryforwards	840.4	$ 795.2
2022
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	13.8
2023
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	13.0
2024
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	13.0
2025
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	15.5
2026
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	10.3
Thereafter
Operating Loss Carryforwards [Line Items]
Tax loss carryforwards, set to expire	$ 502.3