Quarterly report pursuant to Section 13 or 15(d)

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

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Long-Term Debt - Derivative Instruments and Hedging Activities (Details) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Derivatives, Fair Value [Line Items]          
Incremental interest expense $ 0 $ 700,000 $ 100,000 $ 1,900,000  
Net benefit expected to be reclassified 1,800,000   1,800,000    
Interest rate swap and interest rate cap | Derivative instruments and hedging activities          
Derivatives, Fair Value [Line Items]          
Net cash proceeds     4,800,000    
Derivative, Fair Value, Net 8,000,000   8,000,000   $ 4,700,000
Interest rate swap and interest rate cap | Derivative instruments and hedging activities | Other assets          
Derivatives, Fair Value [Line Items]          
Derivative asset, fair value of interest rate swap and cap positions 6,700,000   6,700,000   5,100,000
Interest rate swap and interest rate cap | Derivative instruments and hedging activities | Other current assets          
Derivatives, Fair Value [Line Items]          
Derivative asset, fair value of interest rate swap and cap positions $ 1,300,000   $ 1,300,000    
Interest rate swap | Derivative instruments and hedging activities | Other current assets          
Derivatives, Fair Value [Line Items]          
Derivative liability, fair value of interest rate swap and cap positions         900,000
Interest rate swap | Derivative instruments and hedging activities | Other accrued liabilities          
Derivatives, Fair Value [Line Items]          
Derivative liability, fair value of interest rate swap and cap positions         1,000,000
Interest rate swap | Derivative instruments and hedging activities | Other long-term liabilities          
Derivatives, Fair Value [Line Items]          
Derivative liability, fair value of interest rate swap and cap positions         $ 300,000