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Derivative Financial Instruments Fair Value of the Company's Derivative Instruments (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Interest rate swap agreements [Member]
Derivatives, Fair Value [Line Items]
Derivative Instruments, Loss Reclassified from Accumulated OCI into Income, Effective Portion	$ 200,000	$ 500,000	$ 700,000	$ 900,000
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred			(600,000)
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	69,000		69,000		$ 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	500,000		500,000		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	641,000		641,000		1,972,000
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	1,611,000		1,611,000		12,410,000
Foreign Currency Forward [Member]
Derivatives, Fair Value [Line Items]
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred			400,000
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	411,000		411,000		0
British Pound Foreign currency forward contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred			700,000
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	18,133,000		18,133,000		13,657,000
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	419,000		419,000		829,000
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	14,289,000		14,289,000		5,775,000
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		0		2,887,000
Fair Value, Inputs, Level 2 [Member] \| Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	14,289,000		14,289,000		8,662,000
Fair Value, Inputs, Level 2 [Member] \| Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	19,113,000		19,113,000		13,657,000
Derivative Liability, Fair Value, Gross Liability	$ 2,671,000		$ 2,671,000		$ 15,211,000