MARKETING AGREEMENT - Net Commission Earned Under the Marketing Agreement (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Marketing Agreement [Line Items]
Contribution expenses	$ (3,431.3)	$ (2,768.6)	$ (2,130.5)
Monsanto Marketing Agreement
Marketing Agreement [Line Items]
Gross commission	94.0	90.4	58.4
Contribution expenses	(18.0)	(18.0)	(18.0)
Net commission	76.0	72.4	40.4
Reimbursements associated with Roundup® marketing agreement	70.8	61.6	73.4
Total net sales associated with Roundup® marketing agreement	$ 146.8	$ 134.0	$ 113.8

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 924
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 11.L)
-URI http://asc.fasb.org/extlink&oid=6472922&loc=d3e499488-122856

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(a),(d))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration