Derivative Financial Instruments Fair Value of the Company's Derivative Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 23,198	$ 26,011
Derivative Liability, Fair Value, Gross Liability	32,378	14,454
Designated as Hedging Instrument [Member] | British Pound Foreign currency forward contracts [Member] | Prepaid expenses and other [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	23,198	0
Designated as Hedging Instrument [Member] | British Pound Foreign currency forward contracts [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	26,011
Designated as Hedging Instrument [Member] | British Pound Foreign currency forward contracts [Member] | Accrued expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	191	0
Designated as Hedging Instrument [Member] | British Pound Foreign currency forward contracts [Member] | Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0	59
Designated as Hedging Instrument [Member] | Interest rate swap agreements [Member] | Accrued expenses [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	3,864	1,954
Designated as Hedging Instrument [Member] | Interest rate swap agreements [Member] | Other long-term liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	28,323	12,441
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	13,648	19,684
Not Designated as Hedging Instrument [Member] | Cross-currency swap [Member] | Prepaid expenses and other [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 13,648	$ 19,684