Leases - Cash flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases
Operating cash flows from operating leases	$ 12.0	$ 11.1
Operating cash flows from finance leases	0.1	0.1
Financing cash flows from finance leases	2.9	2.4
Total cash paid for amounts included in the measurement of lease liabilities	15.0	13.6
Finance lease liabilities arising from obtaining right-of-use assets	1.3	3.6
Operating lease liabilities arising from obtaining right-of-use assets	$ 17.4	$ 6.8