Summary of Significant Accounting Policies - Amounts Reclassified out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2023	Aug. 31, 2022	Aug. 31, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest and foreign exchange	$ 85.4	$ 57.4	$ 43.3
Total before tax	(91.0)	(60.6)	8.6
Tax expense (benefit)	24.6	18.1	(40.2)
Unrealized (Gain) Loss on Derivative Financial Instruments | Reclassification out of Accumulated Other Comprehensive loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Total before tax	(12.8)	6.1	6.7
Tax expense (benefit)	3.7	(1.4)	(1.7)
Net of tax	(9.1)	4.7	5.0
Unrealized (Gain) Loss on Derivative Financial Instruments | Reclassification out of Accumulated Other Comprehensive loss | Foreign Exchange Contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Revenue and Cost of revenue	(2.0)	1.2	1.4
Unrealized (Gain) Loss on Derivative Financial Instruments | Reclassification out of Accumulated Other Comprehensive loss | Interest rate swap contracts
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest and foreign exchange	$ (10.8)	$ 4.9	$ 5.3