Derivative Financial Instruments Effect of Derivative Instruments Not Designated as Hedges (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges amount recognized in earnings	$ (18,686)	$ (1,270)	$ (2,269)
Interest (expense)/income | Cross-currency swap agreement [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges amount recognized in earnings	0	(1,184)	(2,696)
Other (expense)/income, net | Cross-currency swap agreement [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges amount recognized in earnings	0	(86)	427
Loss on settlement of foreign currency forward purchase contracts [Member] | British pound forward contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges amount recognized in earnings	$ (18,686)	$ 0	$ 0