Fair Value Measures - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Millions		Nov. 30, 2021	Aug. 31, 2021
Assets:
Nonqualified savings plan investments		$ 47.7	$ 47.7
Fair Value, Measurements, Recurring
Assets:
Derivative financial instruments			0.1
Nonqualified savings plan investments		47.7	47.7
Cash equivalents		169.0	228.9
Assets, Fair Value Disclosure, Total		216.7	276.7
Liabilities:
Derivative financial instruments		12.9	10.5
Fair Value, Inputs, Level 1 | Fair Value, Measurements, Recurring
Assets:
Nonqualified savings plan investments		47.7	47.7
Cash equivalents		169.0	228.9
Assets, Fair Value Disclosure, Total		216.7	276.6
Fair Value, Inputs, Level 2 | Fair Value, Measurements, Recurring
Assets:
Derivative financial instruments	[1]		0.1
Assets, Fair Value Disclosure, Total	[1]		0.1
Liabilities:
Derivative financial instruments	[1]	$ 12.9	$ 10.5

[1] Level 2 assets and liabilities include derivative financial instruments that are valued based on observable inputs. See Note 11 - Derivative Instruments for further discussion.