Long-Term Debt and Capital Leases - Summary (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jul. 17, 2017	May 31, 2017
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 279.6
Long-term debt	2,266.1	$ 2,261.4
Capital lease obligations	2.3	2.8
Total long-term debt and capital lease obligations	2,268.4	2,264.2
Debt issuance costs, net	(11.7)	(13.0)
Sub-total	2,256.7	2,251.2
Less current portion	(23.9)	(24.0)
Long-term portion	$ 2,232.8	2,227.2
Term B Loans
Long-Term Debt and Capital Leases
Effective interest rate (as a percent)	5.30%
Long-term debt	$ 2,251.1	$ 2,261.4
Debt issuance costs, net	(8.5)
Net discount	11.8
Revolving Credit Facility
Long-Term Debt and Capital Leases
Available borrowing capacity	$ 279.6
Effective interest rate (as a percent)	5.10%
Long-term debt	$ 15.0
Debt issuance costs, net	(3.2)
Maximum borrowing capacity	300.0		$ 300.0	$ 200.0
Outstanding letters of credit	$ 5.4