Derivative Financial Instruments - Fair Value Derivatives (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Interest rate swap agreements	$ 1,368	$ 52
Derivatives designated as hedging instruments | Interest rate swap agreements
Derivative [Line Items]
Interest rate swap agreements	1,368	52
Derivative liability	1,845	5,905
Derivatives designated as hedging instruments | Prepaid expenses and other current assets | Interest rate swap agreements
Derivative [Line Items]
Interest rate swap agreements	132	0
Derivatives designated as hedging instruments | Other long-term assets | Interest rate swap agreements
Derivative [Line Items]
Interest rate swap agreements	1,236	52
Derivatives designated as hedging instruments | Accrued other current liabilities | Interest rate swap agreements
Derivative [Line Items]
Derivative liability	19	845
Derivatives designated as hedging instruments | Derivative liabilities | Interest rate swap agreements
Derivative [Line Items]
Derivative liability	$ 1,826	$ 5,060