Accumulated Other Comprehensive Loss - Amounts Reclassified out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	Feb. 28, 2022	Feb. 28, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Interest and foreign exchange	$ 11.8	$ 9.6	$ 24.4	$ 20.7
Total before tax	(13.4)	35.3	(12.6)	48.5
Income tax expense	3.2	(21.8)	1.8	(29.1)
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	1.5	1.7	3.0	3.3
Income tax expense	(0.2)	(0.4)	(0.7)	(0.8)
Net of tax	1.3	1.3	2.3	2.5
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	0.2	0.4	0.4	0.7
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	$ 1.3	$ 1.3	$ 2.6	$ 2.6