Derivative Instruments - Fair Value of Foreign Currency Derivatives (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative assets	$ 11,674	$ 5,591
Derivative liabilities	1,449	149
Total fair value of derivative instruments	10,225	5,442
Cash flow Hedges [Member]
Derivative [Line Items]
Derivative assets	9,337	0
Derivative liabilities	69	0
Balance sheet hedges [Member]
Derivative [Line Items]
Derivative assets	2,337	5,591
Derivative liabilities	$ 1,380	$ 149