Long-Term Debt and Finance Leases - Summary (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 270.7
Long-term debt	1,127.1	$ 2,237.9
Other Financing	0.5	0.8
Finance lease obligations	19.9	32.9
Total long-term debt, finance lease obligations and other	1,147.5	2,271.6
Debt issuance costs, net	(3.7)	(5.6)
Sub-total	1,143.8	2,266.0
Less current portion	(33.9)	(37.5)
Long-term portion	$ 1,109.9	2,228.5
Term B Loans
Long-Term Debt and Capital Leases
Effective interest rate (as a percent)	4.25%
Long-term debt	$ 1,103.1	2,199.9
Debt issuance costs, net	(3.2)	(4.4)
Net discount	4.4	6.1
Revolving Credit Facility
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 270.7
Effective interest rate (as a percent)	3.08%
Long-term debt	$ 24.0	38.0
Debt issuance costs, net	(0.5)	$ (1.2)
Maximum borrowing capacity	300.0
Outstanding letters of credit	$ 5.3