EARNINGS PER COMMON SHARE - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share [Abstract]
Income from continuing operations	$ 517.3	$ 386.9	$ 436.7
Net (income) loss attributable to noncontrolling interest	(0.9)	(1.2)	0.5
Income attributable to controlling interest from continuing operations	516.4	385.7	437.2
Income (loss) from discontinued operations, net of tax	(3.9)	1.7	23.5
Net income attributable to controlling interest	$ 512.5	$ 387.4	$ 460.7
Basic Income (Loss) Per Common Share:
Weighted-average Common Shares outstanding during the period (in shares)	55.7	55.7	55.5
Income from continuing operations (USD per share)	$ 9.27	$ 6.92	$ 7.88
Income (loss) from discontinued operations (USD per share)	(0.07)	0.04	0.42
Basic net income (loss) per common share (USD per share)	$ 9.20	$ 6.96	$ 8.30
Diluted Income (Loss) Per Common Share:
Weighted-average Common Shares outstanding during the period (in shares)	55.7	55.7	55.5
Dilutive potential Common Shares (in shares)	1.5	1.2	0.8
Weighted-average number of Common Shares outstanding and dilutive potential Common Shares (in shares)	57.2	56.9	56.3
Income from continuing operations (USD per share)	$ 9.03	$ 6.78	$ 7.77
Income (loss) from discontinued operations (USD per share)	(0.07)	0.03	0.41
Diluted net income (loss) per common share (USD per share)	$ 8.96	$ 6.81	$ 8.18