Derivatives - Fair Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Designated as hedging instrument | Interest rate swap | Other assets (long-term)
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	$ 5,749	$ 4,991
Designated as hedging instrument | Foreign currency forward contracts | Other assets (long-term)
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	35	18
Designated as hedging instrument | Foreign currency forward contracts | Prepaid expenses and other assets
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	363	116
Designated as hedging instrument | Foreign currency forward contracts | Accrued expenses
Derivatives, Fair Value [Line Items]
Total Liability Derivatives	(468)	(275)
Designated as hedging instrument | Foreign currency forward contracts | Other long-term obligations
Derivatives, Fair Value [Line Items]
Total Liability Derivatives	(82)	(18)
Not designated as hedging instrument | Foreign currency forward contracts | Prepaid expenses and other assets
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	223	220
Not designated as hedging instrument | Foreign currency forward contracts | Accrued expenses
Derivatives, Fair Value [Line Items]
Total Liability Derivatives	$ (841)	$ (171)