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
	Mar. 31, 2015		Mar. 31, 2014
Derivatives designated as hedging instruments
Derivative [Line Items]
Weighted average of U.S. dollar equivalent of foreign denominated net assets	$ 628,941		$ 2,687,455
Derivative gains (losses)	$ 66,770	[1]	$ 960	[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.