Derivative Financial Instruments Effect of Derivative Instruments Not Designated as Hedges (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Other income/(expense), net	$ 2,300	$ 712	$ (827)
Non cash mark to market expense	4,806	14,195
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedges	(54,441)	(5,689)
Not Designated as Hedging Instrument [Member] | Cross-currency swap agreement [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest (expense)/income	(4,638)	(5,935)
Other income/(expense), net	303	246
Fair Value, Inputs, Level 1 [Member] | Not Designated as Hedging Instrument [Member] | Forward Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Non cash mark to market expense	$ (50,106)	$ 0