Derivative Financial Instruments Fair Value of the Company's Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Interest rate swap agreements [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 527	$ 0
Interest rate swap agreements [Member] | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	6,596	0
Interest rate swap agreements [Member] | Designated as Hedging Instrument [Member] | Accrued expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	755	1,972
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	1,706	12,410
Foreign Currency Forward [Member] | Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	383	0
British Pound Foreign currency forward contracts [Member] | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	20,803	13,657
British Pound Foreign currency forward contracts [Member] | Designated as Hedging Instrument [Member] | Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	246	829
Cross-currency swap [Member] | Not Designated as Hedging Instrument [Member] | Prepaid expenses and other [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	16,648	5,775
Cross-currency swap [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	2,887
Fair Value, Inputs, Level 2 [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	16,648	8,662
Fair Value, Inputs, Level 2 [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	28,309	13,657
Derivative Liability, Fair Value, Gross Liability	$ 2,707	$ 15,211