Long-Term Debt and Finance Leases - Summary (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023	Dec. 20, 2021
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 0.4
Long-term debt	951.4	$ 912.3
Other Financing	1.1	1.4
Finance lease obligations	$ 23.6	$ 24.6
Finance Lease, Liability, Statement of Financial Position	Long-term portion, Less current portion	Long-term portion, Less current portion
Total long-term debt, finance lease obligations and other	$ 976.1	$ 938.3
Debt issuance costs, net	(3.1)	(3.8)
Sub-total	973.0	934.5
Less current portion	(17.9)	(18.8)
Long-term portion	$ 955.1	915.7
Term B Loans
Long-Term Debt and Capital Leases
Effective interest rate (as a percent)	7.60%
Long-term debt	$ 706.4	711.3
Debt issuance costs, net	(2.5)	(3.0)
Net discount	3.5	4.1
Revolving Credit Facility
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 0.4
Effective interest rate (as a percent)	7.69%
Long-term debt	$ 245.0	201.0
Debt issuance costs, net	(0.6)	$ (0.8)
Maximum borrowing capacity	250.0		$ 250.0
Outstanding letters of credit	$ 4.6