Basis of Presentation (Policies)	6 Months Ended
Mar. 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.
Restricted Cash	Restricted CashRestricted cash relates to amounts restricted for payment of asbestos liabilities and certain litigation and environmental matters. Restricted cash is recorded primarily within other current assets in the consolidated statements of financial position
Prior Period Revision - Statement of Cash Flows	Prior Period Revision – Statement of Cash FlowsThe 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 six months ended March 31, 2022. Interim and annual amounts for the year ended September 30, 2022 and annual amounts for the years ended September 30, 2021 and 2020 were similarly impacted. Prior period amounts will be revised with future Quarterly Reports on Form 10-Q and Annual Report on Form 10-K filings. Cash provided by financing activities and the total increase (decrease) in cash, cash equivalents and restricted cash were unchanged for all affected periods. The Company does not believe the impact of incorrect presentation is material to any periods.
Recently Issued Accounting Standards	Recently Issued 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 expects to adopt the new disclosures, other than the rollforward disclosure, as required at the beginning of fiscal 2024. The rollforward disclosures will be adopted as required at the beginning of fiscal 2025. 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 March 31, 2023, the aggregate amount of the transaction price allocated to remaining performance obligations was approximately $18.8 billion, of which approximately 65% 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 we expect to recover. Costs to obtain or fulfill a contract are capitalized and amortized over the period of contract performance.
Derivative Instruments and Hedging Activities	As cash flow hedges under ASC 815, "Derivatives and Hedging," hedge gains or losses due to changes in fair value are initially recorded as a component of accumulated other comprehensive income (loss) ("AOCI") and are subsequently reclassified into earnings when the hedged transactions occur and affect earnings.The currency effects of the debt obligations are reflected in AOCI attributable to Johnson Controls ordinary shareholders where they offset currency gains and losses recorded on the Company's net investments globally.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 Foreign currency exchange derivatives: The foreign currency exchange derivatives are valued under a market approach using publicized spot and forward prices. Commodity derivatives: The commodity derivatives are valued under a market approach using publicized prices, where available, or dealer quotes. 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. 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. Investments in 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. 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.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)

6 Months Ended

Mar. 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.

Restricted Cash

Restricted CashRestricted cash relates to amounts restricted for payment of asbestos liabilities and certain litigation and environmental matters. Restricted cash is recorded primarily within other current assets in the consolidated statements of financial position

Prior Period Revision - Statement of Cash Flows

Prior Period Revision – Statement of Cash FlowsThe 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 six months ended March 31, 2022. Interim and annual amounts for the year ended September 30, 2022 and annual amounts for the years ended September 30, 2021 and 2020 were similarly impacted. Prior period amounts will be revised with future Quarterly Reports on Form 10-Q and Annual Report on Form 10-K filings. Cash provided by financing activities and the total increase (decrease) in cash, cash equivalents and restricted cash were unchanged for all affected periods. The Company does not believe the impact of incorrect presentation is material to any periods.

Recently Issued Accounting Standards

Recently Issued 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 expects to adopt the new disclosures, other than the rollforward disclosure, as required at the beginning of fiscal 2024. The rollforward disclosures will be adopted as required at the beginning of fiscal 2025.

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 March 31, 2023, the aggregate amount of the transaction price allocated to remaining performance obligations was approximately $18.8 billion, of which approximately 65% 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 we expect to recover. Costs to obtain or fulfill a contract are capitalized and amortized over the period of contract performance.

Derivative Instruments and Hedging Activities

As cash flow hedges under ASC 815, "Derivatives and Hedging," hedge gains or losses due to changes in fair value are initially recorded as a component of accumulated other comprehensive income (loss) ("AOCI") and are subsequently reclassified into earnings when the hedged transactions occur and affect earnings.The currency effects of the debt obligations are reflected in AOCI attributable to Johnson Controls ordinary shareholders where they offset currency gains and losses recorded on the Company's net investments globally.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

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

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

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.

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.

Investments in 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.

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.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.