Derivative Instruments (Details 4) (Currency Swap [Member], USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Currency Swap [Member]
Net Investments in Foreign Operations [Line Items]
Gains Losses Deferred In Accumulated Other Comprehensive Income Loss On Derivatives	$ (20,470,000)	$ 4,858,000	$ (41,302,000)