Derivative Financial Instruments and Hedging Activities - Narrative (Details) bbl in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Nov. 30, 2017 USD ($)	Aug. 31, 2020 USD ($) bbl	Aug. 31, 2019 USD ($) bbl	Aug. 31, 2018 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Noncurrent, Excluding Fair Value Hedges		$ 21.2	$ 26.6
Annual Payment Receivable Contingent On Investment Credit Rating		5.0
Embedded Derivative, Gain on Embedded Derivative		2.6	2.8	$ 3.1
Payments For Credit Rating Decrease	$ 5.0
Embedded Derivative, Fair Value of Embedded Derivative Asset		19.0
Derivative Liability, Noncurrent, Excluding Fair Value Hedges		5.4	$ 7.4
Interest rate swap gain		$ 16.4
Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Nonmonetary Notional Amount, Volume | bbl		9.7	7.7
Foreign exchange derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount		$ 1,200.0	$ 894.7
Interest rate swap derivatives | Designated as Hedging Instrument | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount		$ 365.0