Basis of Presentation (Policies)	3 Months Ended
Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the consolidated accounts of Johnson Controls International plc and its subsidiaries that are consolidated in conformity with U.S. GAAP. All significant intercompany transactions have been eliminated. The results of companies acquired or disposed of during the reporting period are included in the consolidated financial statements from the effective date of acquisition or up to the date of disposal. Investments in partially-owned affiliates are accounted for by the equity method when the Company exercises significant influence, which typically occurs when its ownership interest exceeds 20%, and the Company does not have a controlling interest. The Company consolidates variable interest entities ("VIE") when it has the power to direct the significant activities of the entity and the obligation to absorb losses or receive benefits from the entity that may be significant. The Company did not have any material consolidated or nonconsolidated VIE's for the presented reporting periods.
Prior Period Revision - Statement of Cash Flows	Prior Period Revision – Statement of Cash Flows The Company revised the amounts previously reported as net proceeds from borrowings with maturities less than three months and proceeds from debt for certain short-term debt transactions that were incorrectly presented on a net basis within the financing activities section of the consolidated statements of cash flows for the three months ended December 30, 2022. The revision did not change cash provided by financing activities or the total decrease in cash, cash equivalents and restricted cash. The Company does not believe the impact of the incorrect presentation was material.
Recently Adopted and Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements In September 2022, the FASB issued ASU 2022-04, "Disclosure of Supplier Finance Program Obligations," which is intended to enhance the transparency surrounding the use of supplier finance programs. Supplier finance programs may also be referred to as reverse factoring, payables finance, or structured payables arrangements. The amendments require a buyer that uses supplier finance programs to make annual disclosures about the program’s key terms, the balance sheet presentation of related amounts, the confirmed amount outstanding at the end of the period, and associated rollforward information. Only the amount outstanding at the end of the period must be disclosed in interim periods. The Company adopted the new disclosures, other than the rollforward disclosure, as required at the beginning of fiscal 2024. The rollforward disclosure will be adopted as required at the beginning of fiscal 2025. The Company maintains agreements with third-party financial institutions who offer voluntary supply chain financing ("SCF") programs to its suppliers. The SCF programs enable suppliers to sell their receivables to third-party financial institutions and receive payments earlier than the negotiated commercial terms between the suppliers and the Company, which generally range from 90 to 120 days. Suppliers sell receivables to third-party financial institutions on terms negotiated between the supplier and the respective third-party financial institution. The Company remains obligated to make payments under the terms of the original commercial arrangement regardless of whether the supplier receivable is sold, and does not pledge any assets as security or provide other forms of guarantees for the committed payment to the third-party financial institutions. Amounts outstanding related to SCF programs are included in accounts payable in the consolidated statements of financial position. Accounts payable included in the SCF programs were approximately $559 million and $566 million as of December 31, 2023, and September 30, 2023, respectively. Recently Issued Accounting Pronouncements In December 2023, the FASB issued ASU 2023-09, "Income Taxes (Topic 740): Improvements to Income Tax Disclosures," which is intended to enhance the transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. The amendments require that on an annual basis, entities disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold. In addition, the amendments require that entities disclose additional information about income taxes paid as well as additional disclosures of pretax income and income tax expense, and remove the requirement to disclose certain items that are no longer considered cost beneficial or relevant. The Company expects to adopt the new annual disclosures as required for fiscal 2026. In November 2023, the FASB issued ASU 2023-07, "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures," which is intended to improve reportable segment disclosures, primarily through enhanced disclosures about significant segment expenses. In addition, the amendments enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss, provide new segment disclosure requirements for entities with a single reportable segment and contain other disclosure requirements. The Company expects to adopt the new annual disclosures as required for fiscal 2025 and the interim disclosures as required beginning with the first quarter of fiscal 2026. Other recently issued accounting pronouncements are not expected to have a material impact on the Company's consolidated financial statements.
Revenue Recognition	Contract Balances Contract assets relate to the Company’s right to consideration for performance obligations satisfied but not billed. Contract liabilities relate to customer payments received in advance of satisfaction of performance obligations under the contract. Contract balances are classified as assets or liabilities on a contract-by-contract basis at the end of each reporting period. Performance Obligations A performance obligation is a distinct good, service, or a bundle of goods and services promised in a contract. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. When contracts with customers require significant and complex integration, contain goods or services which are highly interdependent or interrelated, or are goods or services which significantly modify or customize other promises in the contracts and, therefore, are not distinct, then the entire contract is accounted for as a single performance obligation. For any contracts with multiple performance obligations, the contract’s transaction price is allocated to each performance obligation based on the estimated relative standalone selling price of each distinct good or service in the contract. For product sales, each product sold to a customer typically represents a distinct performance obligation. Performance obligations are satisfied at a point in time or over time. The timing of satisfying the performance obligation is typically stipulated by the terms of the contract. As of December 31, 2023, the aggregate amount of the transaction price allocated to remaining performance obligations was approximately $19.9 billion, of which approximately 64% is expected to be recognized as revenue over the next two years. The remaining performance obligations expected to be recognized in revenue beyond two years primarily relate to large, multi-purpose contracts to construct hospitals, schools and other governmental buildings, which include services to be performed over the building's lifetime, with initial contract terms of 25 to 35 years. Future contract modifications could affect both the timing and the amount of the remaining performance obligations. The Company excludes the value of remaining performance obligations for service contracts with an original expected duration of one year or less. Costs to Obtain or Fulfill a Contract The Company recognizes the incremental costs incurred to obtain or fulfill a contract with a customer as an asset when these costs are recoverable. These costs consist primarily of sales commissions and design costs that relate to a contract or an anticipated contract that the Company expects to recover. Costs to obtain or fulfill a contract are capitalized and amortized over the period of contract performance.
Derivative Instruments and Hedging Activities	The Company holds certain foreign currency forward contracts not designated as hedging instruments under ASC 815 to hedge foreign currency exposure resulting from monetary assets and liabilities denominated in nonfunctional currencies. The changes in fair value of these foreign currency forward exchange derivatives are recorded in the consolidated statements of income where they offset foreign currency transactional gains and losses on the nonfunctional currency denominated assets and liabilities being hedged. The use of derivative financial instruments exposes the Company to counterparty credit risk. The Company has established policies and procedures to limit the potential for counterparty credit risk, including establishing limits for credit exposure and continually assessing the creditworthiness of counterparties. As a matter of practice, the Company deals with major banks worldwide having strong investment grade long-term credit ratings. To further reduce the risk of loss, the Company generally enters into International Swaps and Derivatives Association ("ISDA") master netting agreements with substantially all of its counterparties. The Company enters into ISDA master netting agreements with counterparties that permit the net settlement of amounts owed under the derivative contracts. The master netting agreements generally provide for net settlement of all outstanding contracts with a counterparty in the case of an event of default or a termination event. The Company has not elected to offset the fair value positions of the derivative contracts recorded in the consolidated statements of financial position. The Company's derivative contracts do not contain any credit risk related contingent features and do not require collateral or other security to be furnished by the Company or the counterparties. The Company's exposure to credit risk associated with its derivative instruments is measured on an individual counterparty basis, as well as by groups of counterparties that share similar attributes. The Company does not anticipate any non-performance by any of its counterparties, and the concentration of risk with financial institutions does not present significant credit risk to the Company.
Fair Value Measurements	ASC 820, "Fair Value Measurement," defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. ASC 820 also establishes a three-level fair value hierarchy that prioritizes information used in developing assumptions when pricing an asset or liability as follows: Level 1: Observable inputs such as quoted prices in active markets for identical assets or liabilities; Level 2: Quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and Level 3: Unobservable inputs where there is little or no market data, which requires the reporting entity to develop its own assumptions. ASC 820 requires the use of observable market data, when available, in making fair value measurements. When inputs used to measure fair value fall within different levels of the hierarchy, the level within which the fair value measurement is categorized is based on the lowest level input that is significant to the fair value measurement. Valuation Methods Commodity derivatives: The commodity derivatives are valued under a market approach using publicized prices, where available, or dealer quotes. Contingent earn-out liabilities: The contingent earn-out liabilities were established using a Monte Carlo simulation based on the forecasted operating results and the earn-out formula specified in the purchase agreements. Cross-currency interest rate swaps: The fair value of cross-currency interest rate swaps represents the difference between the swap's reference rate and exchange rate and the interest and exchange rates for a similar instrument as of the reporting period. Cross-currency interest rate swaps are valued under a market approach using publicized prices. Deferred compensation plan assets: Assets held in the deferred compensation plans will be used to pay benefits under certain of the Company's non-qualified deferred compensation plans. The investments primarily consist of mutual funds which are publicly traded on stock exchanges and are valued using a market approach based on the quoted market prices. Unrealized gains (losses) on the deferred compensation plan assets are recognized in the consolidated statements of income where they offset unrealized gains and losses on the related deferred compensation plan liability. Exchange traded funds: Investments in exchange traded funds are valued using a market approach based on quoted market prices, where available, or broker/dealer quotes of identical or comparable instruments. Refer to Note 21, "Commitments and Contingencies," of the notes to the consolidated financial statements for further information. Foreign currency exchange derivatives: The foreign currency exchange derivatives are valued under a market approach using publicized spot and forward prices. Interest rate swaps: The fair value of interest rate swaps represent the difference between the swap's reference rate and the interest rate for a similar instrument as of the reporting period. Interest rate swaps are valued under a market approach using publicized prices. The fair value of public debt was determined primarily using market quotes which are classified as Level 1 inputs within the ASC 820 fair value hierarchy. The fair value of other long-term debt was determined using quoted market prices for similar instruments and are classified as Level 2 inputs within the ASC 820 fair value hierarchy.

Basis of Presentation (Policies)

3 Months Ended

Dec. 31, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The consolidated financial statements include the consolidated accounts of Johnson Controls International plc and its subsidiaries that are consolidated in conformity with U.S. GAAP. All significant intercompany transactions have been eliminated. The results of companies acquired or disposed of during the reporting period are included in the consolidated financial statements from the effective date of acquisition or up to the date of disposal. Investments in partially-owned affiliates are accounted for by the equity method when the Company exercises significant influence, which typically occurs when its ownership interest exceeds 20%, and the Company does not have a controlling interest.

The Company consolidates variable interest entities ("VIE") when it has the power to direct the significant activities of the entity and the obligation to absorb losses or receive benefits from the entity that may be significant. The Company did not have any material consolidated or nonconsolidated VIE's for the presented reporting periods.

Prior Period Revision - Statement of Cash Flows

Prior Period Revision – Statement of Cash Flows

The Company revised the amounts previously reported as net proceeds from borrowings with maturities less than three months and proceeds from debt for certain short-term debt transactions that were incorrectly presented on a net basis within the financing activities section of the consolidated statements of cash flows for the three months ended December 30, 2022.

The revision did not change cash provided by financing activities or the total decrease in cash, cash equivalents and restricted cash. The Company does not believe the impact of the incorrect presentation was material.

Recently Adopted and Recently Issued Accounting Pronouncements

Recently Adopted Accounting Pronouncements

In September 2022, the FASB issued ASU 2022-04, "Disclosure of Supplier Finance Program Obligations," which is intended to enhance the transparency surrounding the use of supplier finance programs. Supplier finance programs may also be referred to as reverse factoring, payables finance, or structured payables arrangements. The amendments require a buyer that uses supplier finance programs to make annual disclosures about the program’s key terms, the balance sheet presentation of related amounts, the confirmed amount outstanding at the end of the period, and associated rollforward information. Only the amount outstanding at the end of the period must be disclosed in interim periods. The Company adopted the new disclosures, other than the rollforward disclosure, as required at the beginning of fiscal 2024. The rollforward disclosure will be adopted as required at the beginning of fiscal 2025.

The Company maintains agreements with third-party financial institutions who offer voluntary supply chain financing ("SCF") programs to its suppliers. The SCF programs enable suppliers to sell their receivables to third-party financial institutions and receive payments earlier than the negotiated commercial terms between the suppliers and the Company, which generally range from 90 to 120 days. Suppliers sell receivables to third-party financial institutions on terms negotiated between the supplier and the respective third-party financial institution. The Company remains obligated to make payments under the terms of the original commercial arrangement regardless of whether the supplier receivable is sold, and does not pledge any assets as security or provide other forms of guarantees for the committed payment to the third-party financial institutions.

Amounts outstanding related to SCF programs are included in accounts payable in the consolidated statements of financial position. Accounts payable included in the SCF programs were approximately $559 million and $566 million as of December 31, 2023, and September 30, 2023, respectively.

Recently Issued Accounting Pronouncements

In December 2023, the FASB issued ASU 2023-09, "Income Taxes (Topic 740): Improvements to Income Tax Disclosures," which is intended to enhance the transparency about income tax information through improvements to income tax disclosures primarily related to the rate reconciliation and income taxes paid information. The amendments require that on an annual basis, entities disclose specific categories in the rate reconciliation and provide additional information for reconciling items that meet a quantitative threshold. In addition, the amendments require that entities disclose additional information about income taxes paid as well as additional disclosures of pretax income and income tax expense, and remove the requirement to disclose certain items that are no longer considered cost beneficial or relevant. The Company expects to adopt the new annual disclosures as required for fiscal 2026.

In November 2023, the FASB issued ASU 2023-07, "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures," which is intended to improve reportable segment disclosures, primarily through enhanced disclosures about significant segment expenses. In addition, the amendments enhance interim disclosure requirements, clarify circumstances in which an entity can disclose multiple segment measures of profit or loss, provide new segment disclosure requirements for entities with a single reportable segment and contain other disclosure requirements. The Company expects to adopt the new annual disclosures as required for fiscal 2025 and the interim disclosures as required beginning with the first quarter of fiscal 2026.

Other recently issued accounting pronouncements are not expected to have a material impact on the Company's consolidated financial statements.

Revenue Recognition

Contract Balances

Contract assets relate to the Company’s right to consideration for performance obligations satisfied but not billed. Contract liabilities relate to customer payments received in advance of satisfaction of performance obligations under the contract. Contract balances are classified as assets or liabilities on a contract-by-contract basis at the end of each reporting period.

Performance Obligations

A performance obligation is a distinct good, service, or a bundle of goods and services promised in a contract. A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. When contracts with customers require significant and complex integration, contain goods or services which are highly interdependent or interrelated, or are goods or services which significantly modify or customize other promises in the contracts and, therefore, are not distinct, then the entire contract is accounted for as a single performance obligation. For any contracts with multiple performance obligations, the contract’s transaction price is allocated to each performance obligation based on the estimated relative standalone selling price of each distinct good or service in the contract. For product sales, each product sold to a customer typically represents a distinct performance obligation.

Performance obligations are satisfied at a point in time or over time. The timing of satisfying the performance obligation is typically stipulated by the terms of the contract. As of December 31, 2023, the aggregate amount of the transaction price allocated to remaining performance obligations was approximately $19.9 billion, of which approximately 64% is expected to be recognized as revenue over the next two years. The remaining performance obligations expected to be recognized in revenue beyond two years primarily relate to large, multi-purpose contracts to construct hospitals, schools and other governmental buildings, which include services to be performed over the building's lifetime, with initial contract terms of 25 to 35 years. Future contract modifications could affect both the timing and the amount of the remaining performance obligations. The Company excludes the value of remaining performance obligations for service contracts with an original expected duration of one year or less.

Costs to Obtain or Fulfill a Contract

The Company recognizes the incremental costs incurred to obtain or fulfill a contract with a customer as an asset when these costs are recoverable. These costs consist primarily of sales commissions and design costs that relate to a contract or an anticipated contract that the Company expects to recover. Costs to obtain or fulfill a contract are capitalized and amortized over the period of contract performance.

Derivative Instruments and Hedging Activities

The Company holds certain foreign currency forward contracts not designated as hedging instruments under ASC 815 to hedge foreign currency exposure resulting from monetary assets and liabilities denominated in nonfunctional currencies. The changes in fair value of these foreign currency forward exchange derivatives are recorded in the consolidated statements of income where they offset foreign currency transactional gains and losses on the nonfunctional currency denominated assets and liabilities being hedged.

The use of derivative financial instruments exposes the Company to counterparty credit risk. The Company has established policies and procedures to limit the potential for counterparty credit risk, including establishing limits for credit exposure and continually assessing the creditworthiness of counterparties. As a matter of practice, the Company deals with major banks worldwide having strong investment grade long-term credit ratings. To further reduce the risk of loss, the Company generally enters into International Swaps and Derivatives Association ("ISDA") master netting agreements with substantially all of its counterparties. The Company enters into ISDA master netting agreements with counterparties that permit the net settlement of amounts owed under the derivative contracts. The master netting agreements generally provide for net settlement of all outstanding contracts with a counterparty in the case of an event of default or a termination event. The Company has not elected to offset the fair value positions of the derivative contracts recorded in the consolidated statements of financial position.

The Company's derivative contracts do not contain any credit risk related contingent features and do not require collateral or other security to be furnished by the Company or the counterparties. The Company's exposure to credit risk associated with its derivative instruments is measured on an individual counterparty basis, as well as by groups of counterparties that share similar attributes. The Company does not anticipate any non-performance by any of its counterparties, and the concentration of risk with financial institutions does not present significant credit risk to the Company.

Fair Value Measurements

ASC 820, "Fair Value Measurement," defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. ASC 820 also establishes a three-level fair value hierarchy that prioritizes information used in developing assumptions when pricing an asset or liability as follows:

Level 1: Observable inputs such as quoted prices in active markets for identical assets or liabilities;

Level 2: Quoted prices in active markets for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or inputs, other than quoted prices in active markets, that are observable either directly or indirectly; and

Level 3: Unobservable inputs where there is little or no market data, which requires the reporting entity to develop its own assumptions.

ASC 820 requires the use of observable market data, when available, in making fair value measurements. When inputs used to measure fair value fall within different levels of the hierarchy, the level within which the fair value measurement is categorized is based on the lowest level input that is significant to the fair value measurement.

Valuation Methods

Commodity derivatives: The commodity derivatives are valued under a market approach using publicized prices, where available, or dealer quotes.

Contingent earn-out liabilities: The contingent earn-out liabilities were established using a Monte Carlo simulation based on the forecasted operating results and the earn-out formula specified in the purchase agreements.

Cross-currency interest rate swaps: The fair value of cross-currency interest rate swaps represents the difference between the swap's reference rate and exchange rate and the interest and exchange rates for a similar instrument as of the reporting period. Cross-currency interest rate swaps are valued under a market approach using publicized prices.

Deferred compensation plan assets: Assets held in the deferred compensation plans will be used to pay benefits under certain of the Company's non-qualified deferred compensation plans. The investments primarily consist of mutual funds

which are publicly traded on stock exchanges and are valued using a market approach based on the quoted market prices. Unrealized gains (losses) on the deferred compensation plan assets are recognized in the consolidated statements of income where they offset unrealized gains and losses on the related deferred compensation plan liability.

Exchange traded funds: Investments in exchange traded funds are valued using a market approach based on quoted market prices, where available, or broker/dealer quotes of identical or comparable instruments. Refer to Note 21, "Commitments and Contingencies," of the notes to the consolidated financial statements for further information.

Foreign currency exchange derivatives: The foreign currency exchange derivatives are valued under a market approach using publicized spot and forward prices.

Interest rate swaps: The fair value of interest rate swaps represent the difference between the swap's reference rate and the interest rate for a similar instrument as of the reporting period. Interest rate swaps are valued under a market approach using publicized prices.

The fair value of public debt was determined primarily using market quotes which are classified as Level 1 inputs within the ASC 820 fair value hierarchy. The fair value of other long-term debt was determined using quoted market prices for similar instruments and are classified as Level 2 inputs within the ASC 820 fair value hierarchy.