Derivative Financial Instruments and Hedging Activities - Pretax Gains (Losses) on Derivatives Accounted for as Hedging Instruments (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	$ 0	$ 0	$ 0
Interest expense | Interest rate swap derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	18,723	12,806	(9,842)
Interest expense | Hedged item
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Fair Value Hedges Recognized in Earnings	$ (18,723)	$ (12,806)	$ 9,842