Long-Term Debt and Finance Leases - Summary (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 235.6
Long-term debt	2,253.7	$ 2,237.9
Other Financing	0.7	0.8
Finance lease obligations	32.2	32.9
Total long-term debt, finance lease obligations and other	2,286.6	2,271.6
Debt issuance costs, net	(5.0)	(5.6)
Sub-total	2,281.6	2,266.0
Less current portion	(38.4)	(37.5)
Long-term portion	$ 2,243.2	2,228.5
Term B Loans
Long-Term Debt and Capital Leases
Effective interest rate (as a percent)	5.28%
Long-term debt	$ 2,194.7	2,199.9
Debt issuance costs, net	(4.0)	(4.4)
Net discount	5.5	6.1
Revolving Credit Facility
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 235.6
Effective interest rate (as a percent)	3.11%
Long-term debt	$ 59.0	38.0
Debt issuance costs, net	(1.0)	$ (1.2)
Maximum borrowing capacity	300.0
Outstanding letters of credit	$ 5.4