Guarantees (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023
Guarantees [Abstract]
Maximum length, in years, of a product warranty for it to be recorded in other current liabilities	1 year
Minimum length, in years, of a product warranty for it to be recorded in other noncurrent liabilities	1 year
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at beginning of period	$ 91	$ 66
Accruals for warranties issued during the period	85	72
Settlements made (in cash or in kind) during the period	(87)	(46)
Changes in estimates to pre-existing warranties	31	(2)
Accruals from acquisitions and divestitures	0	1
Currency translation	2	0
Balance at end of period	$ 122	$ 91

Maximum length, in years, of a product warranty for it to be recorded in other current liabilities.

No definition available.

Name:	jci_MaximumLengthInYearsOfProductWarrantyForItToBeRecordedInOtherCurrentLiabilities
Namespace Prefix:	jci_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum length, in years, of a product warranty for it to be recorded in other noncurrent liabilities.

+ References

No definition available.

+ Details

Name:	jci_MinimumLengthInYearsOfProductWarrantyForItToBeRecordedInOtherNoncurrentLiabilities
Namespace Prefix:	jci_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Product warranty accrual additions from business acquisitions and reductions from business divestitures.

+ References

No definition available.

+ Details

Name:	jci_ProductWarrantyAccrualAdditionsFromBusinessAcquisitionAndDivestitures
Namespace Prefix:	jci_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

+ Details

Name:	us-gaap_GuaranteesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_MovementInStandardProductWarrantyAccrualRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount as of the balance sheet date of the aggregate standard product warranty liability. Does not include the balance for the extended product warranty liability.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-8

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (c)(5)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-8

+ Details

Name:	us-gaap_StandardProductWarrantyAccrual
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of foreign currency translation gain (loss) which decreases (increases) the standard product warranty accrual. Excludes extended product warranties.

+ References

+ Details

Name:	us-gaap_StandardProductWarrantyAccrualForeignCurrencyTranslationGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of decrease in the standard product warranty accrual from payments made in cash or in kind to satisfy claims under the terms of the standard product warranty. Excludes extended product warranties.

+ References

+ Details

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

- Definition

Amount of increase (decrease) in the standard product warranty accrual from changes in estimates attributable to preexisting product warranties. Excludes extended product warranties.

+ References

+ Details

Name:	us-gaap_StandardProductWarrantyAccrualPreexistingIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase in the standard product warranty accrual from warranties issued. Excludes extended product warranties.

+ References

+ Details

Name:	us-gaap_StandardProductWarrantyAccrualWarrantiesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration