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	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017		Jun. 30, 2016
Derivative [Line Items]
Weighted average of U.S. dollar equivalent of foreign denominated net assets	$ 1,659,312	$ 2,394,185	$ 1,668,229		$ 2,314,466
Derivative gains (losses)	$ (49,370)	$ 45,397	$ (78,767)	[1]	$ 33,882	[1]

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