Other assets - Schedule of Intangible Assets (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 2.0	$ 2.0
Less - accumulated amortization	(0.3)	(0.2)
Intangible assets, net	1.7	1.8
Internal-use software
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	0.7	0.7
Cloud computing arrangements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 1.3	$ 1.3