Acquisitions and Divestitures - Additional Information (Detail) - USD ($) $ in Millions	6 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Acquisitions And Divestitures [Line Items]
Cash paid for business acquisition	$ 124	$ 10
Goodwill, Acquired During Period	123
Business divestitures, net of cash divested	16	19
Goodwill, Written off Related to Sale of Business Unit	98
Global Products
Acquisitions And Divestitures [Line Items]
Goodwill, Acquired During Period	16
Goodwill, Written off Related to Sale of Business Unit	0
Building Solutions Asia Pacific
Acquisitions And Divestitures [Line Items]
Goodwill, Acquired During Period	45
Goodwill, Written off Related to Sale of Business Unit	16
Building Solutions EMEA/LA
Acquisitions And Divestitures [Line Items]
Goodwill, Acquired During Period	38
Goodwill, Written off Related to Sale of Business Unit	82
Building Solutions North America
Acquisitions And Divestitures [Line Items]
Goodwill, Acquired During Period	24
Goodwill, Written off Related to Sale of Business Unit	0
Business Divestitures, Not Specific \| Building Solutions Asia Pacific
Acquisitions And Divestitures [Line Items]
Proceeds from Divestiture of Businesses		23
Business divestitures, net of cash divested		19
Goodwill, Written off Related to Sale of Business Unit		6
Business Divestitures, Not Specific \| Building Solutions EMEA/LA
Acquisitions And Divestitures [Line Items]
Proceeds from Divestiture of Businesses	18
Business divestitures, net of cash divested	16
Goodwill, Written off Related to Sale of Business Unit	5
Individually Immaterial Acquisitions
Acquisitions And Divestitures [Line Items]
Purchase price, net of cash acquired	160	15
Cash paid for business acquisition	124	10
Individually Immaterial Acquisitions \| Building Solutions Asia Pacific
Acquisitions And Divestitures [Line Items]
Goodwill, Acquired During Period	45
Individually Immaterial Acquisitions \| Building Solutions EMEA/LA
Acquisitions And Divestitures [Line Items]
Goodwill, Acquired During Period	29	$ 13
Individually Immaterial Acquisitions \| Building Solutions North America
Acquisitions And Divestitures [Line Items]
Goodwill, Acquired During Period	$ 24

Acquisitions And Discontinued Operations [Line Items]

No definition available.

Name:	jci_AcquisitionsAndDiscontinuedOperationsLineItems
Namespace Prefix:	jci_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

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

- Definition

Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267

+ Details

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

- Definition

The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3213-108585

+ Details

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

- Definition

This element represents the cash inflow during the period from the sale of a component of the entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3179-108585

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jci_GlobalProductsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jci_BuildingSolutionsAsiaPacificMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jci_BuildingSolutionsEMEALAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jci_BuildingSolutionsNorthAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=jci_BusinessDivestituresNotSpecificMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=us-gaap_SeriesOfIndividuallyImmaterialBusinessAcquisitionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: