Derivative Financial Instruments Fair Value of the Company's Derivative Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Interest rate swap agreements [Member] | Designated as Hedging Instrument [Member] | Accrued expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 2,338	$ 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	15,493	13,411
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	20,287	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	234	17
Currency Swap [Member] | Not Designated as Hedging Instrument [Member] | Other assets, net [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	254	506
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	259	174
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	20,287	26,359
Derivative Liability, Fair Value, Gross Liability	18,065	15,175
Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 513	$ 680