Special Charges (Details) - USD ($) $ in Millions	3 Months Ended
	Nov. 30, 2019	Nov. 30, 2018
Restructuring Cost and Reserve [Line Items]
Special charges	$ 6.9	$ 1.0
Restructuring Reserve [Roll Forward]
Balance, beginning of period	1.9
Severance costs	5.1
Payments made during the period	(2.2)
Balance, end of period	4.8
Fiscal 2020 Actions
Restructuring Reserve [Roll Forward]
Balance, beginning of period	0.0
Severance costs	5.1
Payments made during the period	(1.0)
Balance, end of period	4.1
Fiscal 2019 Actions
Restructuring Reserve [Roll Forward]
Balance, beginning of period	1.3
Severance costs	0.0
Payments made during the period	(0.8)
Balance, end of period	0.5
Fiscal 2018 Actions
Restructuring Reserve [Roll Forward]
Balance, beginning of period	0.6
Severance costs	0.0
Payments made during the period	(0.4)
Balance, end of period	0.2
Severance and employee-related costs
Restructuring Cost and Reserve [Line Items]
Special charges	5.1	(0.5)
Other restructuring costs
Restructuring Cost and Reserve [Line Items]
Special charges	$ 1.8	$ 1.5