SEGMENT INFORMATION - Segment Financial Information (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Segment Reporting Information [Line Items]
Net sales	$ 3,551.3	$ 3,924.1	$ 4,925.0
Intangible asset amortization	(25.2)	(37.1)	(30.9)
Impairment, restructuring and other	(280.5)	(693.1)	(4.3)
Equity in income (loss) of unconsolidated affiliates	(101.1)	(12.9)	14.4
Interest expense	(178.1)	(118.1)	(78.9)
Other non-operating income, net	0.3	6.9	18.6
Depreciation and amortization	92.5	105.2	93.8
Capital expenditures	92.8	113.5	106.9
Assets	3,413.7	4,296.8
Corporate
Segment Reporting Information [Line Items]
Depreciation and amortization	2.9	7.6	7.9
Assets	346.1	583.8
U.S. Consumer
Segment Reporting Information [Line Items]
Net sales	2,843.7	2,928.8	3,197.7
Capital expenditures	79.6	97.4	78.3
U.S. Consumer | Operating Segments
Segment Reporting Information [Line Items]
Depreciation and amortization	58.2	55.8	48.6
Assets	2,296.2	2,454.4
Hawthorne
Segment Reporting Information [Line Items]
Net sales	467.3	716.2	1,424.2
Capital expenditures	8.5	12.4	25.0
Hawthorne | Operating Segments
Segment Reporting Information [Line Items]
Depreciation and amortization	25.8	34.8	30.3
Assets	581.6	1,061.5
Other
Segment Reporting Information [Line Items]
Net sales	240.3	279.1	303.1
Capital expenditures	4.7	3.7	3.6
Other | Operating Segments
Segment Reporting Information [Line Items]
Depreciation and amortization	5.6	7.0	7.0
Assets	189.8	197.1
Continuing Operations
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes	(453.3)	(558.1)	677.1
Intangible asset amortization	(25.2)	(37.1)	(30.9)
Impairment, restructuring and other	(466.0)	(852.2)	(29.0)
Equity in income (loss) of unconsolidated affiliates	(101.1)	(12.9)	14.4
Interest expense	(178.1)	(118.1)	(78.9)
Other non-operating income, net	0.3	6.9	18.6
Continuing Operations | Operating Segments
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes	418.4	567.7	932.6
Continuing Operations | Corporate
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes	(101.6)	(112.4)	(149.7)
Continuing Operations | U.S. Consumer | Operating Segments
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes	454.1	568.6	726.7
Continuing Operations | Hawthorne | Operating Segments
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes	(48.1)	(21.1)	163.8
Continuing Operations | Other | Operating Segments
Segment Reporting Information [Line Items]
Income from continuing operations before income taxes	$ 12.4	$ 20.2	$ 42.1