Annual report pursuant to Section 13 and 15(d)

Long-Term Debt - Derivative Instruments and Hedging Activities Narrative (Details)

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Long-Term Debt - Derivative Instruments and Hedging Activities Narrative (Details) - USD ($)
$ in Millions
12 Months Ended
Mar. 09, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Derivatives, Fair Value [Line Items]        
Cash premiums paid   $ 2.8 $ 1.9  
Unamortized premium   4.6 1.9  
Incremental interest expense   0.2 3.1 $ 5.5
Net benefit expected to be reclassified   2.9    
Designated as hedging instrument | Cash flow swaps and interest rate caps        
Derivatives, Fair Value [Line Items]        
Net cash proceeds $ 4.8      
Derivative asset, fair value of interest rate swap and cap positions   4.8    
Designated as hedging instrument | Interest rate swap        
Derivatives, Fair Value [Line Items]        
Derivative liability, fair value of interest rate swap and cap positions     4.7  
Designated as hedging instrument | Other current assets | Cash flow swaps and interest rate caps        
Derivatives, Fair Value [Line Items]        
Derivative asset, fair value of interest rate swap and cap positions   1.8    
Designated as hedging instrument | Other current assets | Interest rate swap        
Derivatives, Fair Value [Line Items]        
Derivative liability, fair value of interest rate swap and cap positions     0.9  
Designated as hedging instrument | Other assets | Cash flow swaps and interest rate caps        
Derivatives, Fair Value [Line Items]        
Derivative asset, fair value of interest rate swap and cap positions   $ 3.0    
Designated as hedging instrument | Other assets | Interest rate swap        
Derivatives, Fair Value [Line Items]        
Derivative asset, fair value of interest rate swap and cap positions     5.1  
Designated as hedging instrument | Other accrued liabilities | Interest rate swap        
Derivatives, Fair Value [Line Items]        
Derivative liability, fair value of interest rate swap and cap positions     1.0  
Designated as hedging instrument | Other long-term liabilities | Interest rate swap        
Derivatives, Fair Value [Line Items]        
Derivative liability, fair value of interest rate swap and cap positions     $ 0.3