Derivative Financial Instruments Effect of Cash Flow Hedges in OCI (Details) - Other Comprehensive Income (Loss) [Member] - Cash Flow Hedging [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivatives [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ (3,837)	$ (23,473)	$ 20,988
Designated as Hedging Instrument [Member] | Interest rate swap agreement [Member]
Derivatives [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	(4,749)	(23,473)	20,988
Designated as Hedging Instrument [Member] | British pound forward contracts [Member]
Derivatives [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	$ 912	$ 0	$ 0