Derivative Financial Instruments and Hedging Activities - Narrative (Details) $ in Millions	3 Months Ended					12 Months Ended
	Nov. 30, 2017 USD ($)	Nov. 30, 2016 USD ($)	May 31, 2016 USD ($) derivative	Feb. 29, 2016 USD ($) derivative	Nov. 30, 2015 USD ($) derivative	Aug. 31, 2018 USD ($)	Aug. 31, 2017 USD ($)	Aug. 31, 2015 USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Asset, Noncurrent, Excluding Fair Value Hedges						$ 23.1	$ 30.9
Annual Payment Receivable Contingent On Investment Credit Rating						5.0
Embedded Derivative, Gain on Embedded Derivative		$ 29.1					30.5
Payments For Credit Rating Decrease	$ 5.0	$ 5.0
Embedded Derivative, Fair Value of Embedded Derivative Asset						23.6
Derivative Liability, Noncurrent, Excluding Fair Value Hedges						7.9	12.3
Foreign exchange derivatives | Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount						988.8	$ 776.7
Interest rate swap derivatives | Designated as Hedging Instrument | Fair Value Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount						$ 495.0
Interest rate swap derivatives | Designated as Hedging Instrument | Cash Flow Hedging [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative, Notional Amount								$ 300.0
Cash paid to settle derivatives			$ 5.1	$ 5.3	$ 6.4
Derivatives settled, number | derivative			2	2	2