Derivatives - Fair Value of Derivative Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Designated as hedging instrument | Interest rate swap | Other assets (long-term)
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	$ 8,047	$ 5,749
Designated as hedging instrument | Foreign currency forward contracts | Other assets (long-term)
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	83	35
Designated as hedging instrument | Foreign currency forward contracts | Prepaid expenses and other assets
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	700	363
Designated as hedging instrument | Foreign currency forward contracts | Accrued expenses
Derivatives, Fair Value [Line Items]
Total Liability Derivatives	(231)	(468)
Designated as hedging instrument | Foreign currency forward contracts | Other long-term obligations
Derivatives, Fair Value [Line Items]
Total Liability Derivatives	(38)	(82)
Not designated as hedging instrument | Foreign currency forward contracts | Prepaid expenses and other assets
Derivatives, Fair Value [Line Items]
Total Asset Derivatives	1,097	223
Not designated as hedging instrument | Foreign currency forward contracts | Accrued expenses
Derivatives, Fair Value [Line Items]
Total Liability Derivatives	$ (228)	$ (841)