Derivative Instruments - Derivative Instruments Designated as Hedges of the net Investment In a Foreign Operation - Summary (Details) (Derivatives designated as hedging instruments, USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Derivatives designated as hedging instruments
Derivative [Line Items]
Weighted average of U.S. dollar equivalent of foreign denominated net assets	$ 2,588,385		$ 1,872,407		$ 2,566,103		$ 1,882,904
Derivative gains (losses)	$ (6,135)	[1]	$ 56,777	[1]	$ 54,479	[1]	$ 18,905	[1]

[1] Derivative gains (losses) from derivative instruments designated as hedges of the net investment in a foreign operation are recorded in the cumulative translation adjustment account within AOCI for each period.