Derivative Financial Instruments and Hedging Activities - Fair Value of Derivative Instruments Designated as Fair Value Hedges (Details) - USD ($) $ in Thousands	Aug. 31, 2019	Aug. 31, 2018
Derivative [Line Items]
Derivative asset	$ 246,728	$ 352,029
Derivative liability	244,019	445,755
Designated as Hedging Instrument | Interest rate swap derivatives
Derivative [Line Items]
Derivative asset	9,841	0
Derivative liability	0	9,452
Designated as Hedging Instrument | Derivative assets | Interest rate swap derivatives
Derivative [Line Items]
Derivative asset	0	0
Designated as Hedging Instrument | Derivative liabilities | Interest rate swap derivatives
Derivative [Line Items]
Derivative liability	0	771
Designated as Hedging Instrument | Other assets | Interest rate swap derivatives
Derivative [Line Items]
Derivative asset	9,841	0
Designated as Hedging Instrument | Other liabilities | Interest rate swap derivatives
Derivative [Line Items]
Derivative liability	0	8,681
Cash Flow Hedging [Member] | Designated as Hedging Instrument
Derivative [Line Items]
Derivative asset	33,179	812
Derivative liability	$ 5,351	$ 634