Fair Value Measurements (Details) - USD ($) $ in Millions	Sep. 30, 2020		Dec. 31, 2019
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	$ 349.2		$ 3.7
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	4,052.2		3,798.3
Finance Lease, Liability, Noncurrent	6.3		6.8
Unamortized Debt Issuance Costs	6.2		6.4
Carrying Amount
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	349.2		3.7
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	3,769.5	[1]	3,565.7	[2]
Fair Value | Fair Value, Inputs, Level 1
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	349.2		3.7
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	0.0		0.0
Fair Value | Fair Value, Inputs, Level 2
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	0.0		0.0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	4,052.2		3,798.3
Fair Value | Fair Value, Inputs, Level 3
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Cash and Cash Equivalents - Fair Value	0.0		0.0
Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract]
Debt Instrument, Fair Value Disclosure	$ 0.0		$ 0.0

[1] The carrying amount of long-term debt excludes a $6.3 million long-term finance lease obligation and $6.2 million of unamortized debt issuance costs.

[2] The carrying amount of long-term debt excludes a $6.8 million long-term finance lease obligation and $6.4 million of unamortized debt issuance costs.