Leases and commitments - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
Operating lease right-of-use assets	$ 35.4	$ 42.5
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other accrued liabilities	Other accrued liabilities
Other accrued liabilities	$ 19.1	$ 26.0
Long-term operating lease liabilities	25.6	29.7
Total operating lease liabilities	$ 44.7	$ 55.7
Finance Leases
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Outsourcing assets, net	Outsourcing assets, net
Outsourcing assets, net	$ 0.1	$ 0.4
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current maturities of long-term debt	Current maturities of long-term debt
Current maturities of long-term debt	$ 0.3	$ 0.7
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term debt	Long-term debt
Long-term debt	$ 0.0	$ 0.4
Total finance lease liabilities	$ 0.3	$ 1.1
Weighted-Average Remaining Lease Term (in years)
Operating leases	3 years 6 months	2 years 6 months
Finance leases	6 months	1 year 4 months 24 days
Weighted-Average Discount Rate
Operating leases (as a percentage)	8.30%	6.70%
Finance Leases (as a percentage)	5.20%	5.10%