Derivative Instruments and Hedging Activities Derivatives - Balance Sheet Impact (Details) - USD ($) $ in Thousands	May 31, 2017	May 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets	$ 49,481	$ 80,095
Derivative Asset, Notional Amount	3,754,120	2,879,567
Derivative liabilities	385,337	594,820
Derivative Liability, Notional Amount	7,037,276	7,320,904
Derivative Assets (Liabilities), at Fair Value, Net	(335,856)	(514,725)
Derivative, Notional Amount	$ 10,791,396	$ 10,200,471