Derivative Financial Instruments Fair Value of the Company's Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
British pound forward contracts [Member] | Designated as Hedging Instrument [Member] | Other assets, net [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 16,017	$ 26,359
British pound forward contracts [Member] | Designated as Hedging Instrument [Member] | Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	568	17
Cross-currency swap [Member] | Not Designated as Hedging Instrument [Member] | Other assets, net [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	944	506
Cross-currency swap [Member] | Not Designated as Hedging Instrument [Member] | Prepaid Expenses and Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,259	174
Interest rate swap agreements [Member] | Designated as Hedging Instrument [Member] | Accrued expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	2,005	1,747
Interest rate swap agreements [Member] | Designated as Hedging Instrument [Member] | Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	15,425	13,411
Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,203	680
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	16,017	26,359
Derivative Liability, Fair Value, Gross Liability	$ 17,998	$ 15,175