Derivative Financial Instruments Derivative Instruments Designated as Cash Flow Hedges OCI Activity (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Effective portion of changes in fair value recognized in OCI:	$ (6,311,000)	$ (6,959,000)
Derivative designated as cash flow hedges [Member] | Interest rate swap agreements [Member]
Derivative [Line Items]
Effective portion of changes in fair value recognized in OCI:	(5,839,000)	(6,959,000)
Derivative designated as cash flow hedges [Member] | British pound forward purchase contracts [Member]
Derivative [Line Items]
Effective portion of changes in fair value recognized in OCI:	$ (472,000)	$ 0