Represents the amount gain (loss) on debt securities repurchased.

No definition available.

Name:	csan_GainLossOnRepurchaseOfDebtSecurities
Namespace Prefix:	csan_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of prize on debt securities repurchased.

+ References

No definition available.

+ Details

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Namespace Prefix:	csan_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of debt securities repurchased.

+ References

No definition available.

+ Details

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Namespace Prefix:	csan_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the amount of premium on debt securities repurchased.

+ References

No definition available.

+ Details

Name:	csan_RepurchaseOfDebtSecuritiesPremium
Namespace Prefix:	csan_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The interest rate on borrowings. [Refer: Borrowings]

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IFRS
-Number 7
-IssueDate 2024-01-01
-Paragraph 7
-URI https://taxonomy.ifrs.org/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2024-en-r&anchor=para_7&doctype=Standard
-URIDate 2024-03-27

+ Details

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Data Type:	dtr-2022:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with members defined in one or many axes of the table.

+ References

No definition available.

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow for interest paid, classified as financing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 7
-IssueDate 2024-01-01
-Paragraph 31
-URI https://taxonomy.ifrs.org/xifrs-link?type=IAS&num=7&code=ifrs-tx-2024-en-r&anchor=para_31&doctype=Standard
-URIDate 2024-03-27

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	ifrs-full_NonadjustingEventsAfterReportingPeriodAxis=csan_DebtRepurchaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=csan_SeniorNotesDue2029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_SignificantInvestmentsInSubsidiariesAxis=csan_CosanLuxembourgSAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ifrs-full_BorrowingsByNameAxis=csan_SeniorNotesDue2030Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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SUBSEQUENT EVENTS - Schedule of amount offered for repurchase of debt (Detail) R$ in Thousands, $ in Thousands			3 Months Ended	12 Months Ended
	Feb. 12, 2025 BRL (R$)	Feb. 12, 2025 USD ($)	Mar. 31, 2025 BRL (R$)	Dec. 31, 2024 BRL (R$)	Dec. 31, 2023 BRL (R$)	Dec. 31, 2022 BRL (R$)
Subsequent events
Added value of principal			R$ 1,152,469
Added value paid in the repurchase			1,152,469
Interest paid			52,384	R$ 377,269	R$ 236,948	R$ 211,611
Premium			(17,714)
Gain/Loss			R$ (17,714)
Debt Repurchase Member
Subsequent events
Added value of principal	R$ 3,462,660	$ 600,000
Debt Repurchase Member \| Senior Notes Due 2029 [Member] \| Cosan Luxembourg S A [member]
Subsequent events
Borrowings, interest rate			5.50%
Added value of principal			R$ 1,347,741
Added value paid in the repurchase			1,228,072
Interest paid			30,487
Premium			67,135
Gain/Loss			R$ 52,534
Debt Repurchase Member \| Senior Notes Due 2030 [Member] \| Cosan Luxembourg S A [member]
Subsequent events
Borrowings, interest rate			7.50%
Added value of principal			R$ 1,568,974
Added value paid in the repurchase			1,541,476
Interest paid			16,842
Premium			78,522
Gain/Loss			R$ (51,024)
Debt Repurchase Member \| Senior Notes Due 2031 [Member] \| Cosan Luxembourg S A [member]
Subsequent events
Borrowings, interest rate			7.25%
Added value of principal			R$ 1,594,064
Added value paid in the repurchase			1,544,299
Interest paid			16,798
Premium			79,604
Gain/Loss			R$ (29,839)