Fair Value Measures - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Feb. 28, 2023	Aug. 31, 2022
Assets:
Nonqualified savings plan investments		$ 45.1	$ 40.3
Fair Value, Measurements, Recurring
Assets:
Derivative financial instruments		37.9	21.4
Nonqualified savings plan investments		45.1	40.3
Cash equivalents		60.3	119.4
Assets, Fair Value Disclosure, Total		143.3	181.1
Liabilities:
Derivative financial instruments		0.4	3.0
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Assets:
Nonqualified savings plan investments		45.1	40.3
Cash equivalents		60.3	119.4
Assets, Fair Value Disclosure, Total		105.4	159.7
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Assets:
Derivative financial instruments	[1]	37.9	21.4
Assets, Fair Value Disclosure, Total	[1]	37.9	21.4
Liabilities:
Derivative financial instruments	[1]	$ 0.4	$ 3.0

[1] Level 2 assets and liabilities include derivative financial instruments that are valued based on observable inputs. See Note 12 - Derivative Instruments for further discussion.