Long-Term Debt - Swap Agreements in the Consolidated Balance Sheets (Details) - Interest Rate Swap - Designated as Hedging Instrument - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Prepaid expenses and other current assets
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$ 0.5	$ 0.0
Other non-current assets
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	6.2	6.7
Other non-current liabilities
Derivatives, Fair Value [Line Items]
Derivative liability, fair value	$ 4.5	$ 0.0