Variable and voting interest entities - Total assets and maximum exposure to loss for unconsolidated variable interest entities (Details) - Other long-term investments - Variable Interest Entity, Not Primary Beneficiary, Excluding Investments In Related Party Investment Funds - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Total VIE Assets
Total VIE Assets	$ 211.5	$ 211.5
Maximum Exposure to Loss
On-Balance Sheet	144.0	144.0
Off-Balance Sheet	2.0	2.0
Total	$ 146.0	$ 146.0