Basis of Presentation (Policies)	6 Months Ended
Mar. 31, 2026
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 in conformity with U.S. GAAP. 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.
Recently Adopted and Recently Issued Accounting Pronouncements	Recently Adopted Accounting Pronouncements 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 adopted the new annual disclosures as required for fiscal 2025 and the interim disclosures as required in the first quarter of fiscal 2026. Refer to Note 16, "Segment Information," of the notes to consolidated financial statements for the Company's segment disclosures. 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 2024, the FASB issued ASU 2024-03, "Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses," which is intended to enhance transparency into the nature and function of expenses. The amendments require that on an annual and interim basis, entities disclose disaggregated operating expense information about specific categories, including purchases of inventory, employee compensation, depreciation, amortization and depletion. The Company expects to adopt the new annual disclosures as required for fiscal 2028 and the interim disclosures as required beginning with the first quarter of fiscal 2029. In September 2025, the FASB issued ASU 2025-06, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software," which is intended to increase the operability of the recognition guidance considering different methods of software development. The amendments remove all references to prescriptive and sequential software development stages (referred to as “project stages”) throughout Subtopic 350-40, and instead specify an entity is required to start capitalizing software costs when both of the following occur: (1) management has authorized and committed to funding the software project and (2) it is probable that the project will be completed and the software will be used to perform the function intended (referred to as the “probable-to complete recognition threshold”). The Company expects to adopt the new guidance as required for fiscal 2029 and is evaluating the impact the new standard will have on its consolidated financial statements. 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 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, 2026, the aggregate amount of the transaction price allocated to remaining performance obligations was approximately $26.3 billion, of which approximately 67% 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 construction contracts, 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 of service contracts with a duration of one year or less and open purchase orders from the indirect third-party sales channel that have a short cycle time (generally 60 days 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 when incurred and amortized to expense over the period of contract performance.
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 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. 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. Derivatives: Derivatives consist primarily of foreign currency exchange derivatives and are valued under a market approach using publicly available prices, where available, or dealer quotes. 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.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, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The consolidated financial statements include the consolidated accounts of Johnson Controls International plc and its subsidiaries in conformity with U.S. GAAP. 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.

Recently Adopted and Recently Issued Accounting Pronouncements

Recently Adopted Accounting Pronouncements

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 adopted the new annual disclosures as required for fiscal 2025 and the interim disclosures as required in the first quarter of fiscal 2026. Refer to Note 16, "Segment Information," of the notes to consolidated financial statements for the Company's segment disclosures.

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 2024, the FASB issued ASU 2024-03, "Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses," which is intended to enhance transparency into the nature and function of expenses. The amendments require that on an annual and interim basis, entities disclose disaggregated operating expense information about specific categories, including purchases of inventory, employee compensation, depreciation, amortization and depletion. The Company expects to adopt the new annual disclosures as required for fiscal 2028 and the interim disclosures as required beginning with the first quarter of fiscal 2029.

In September 2025, the FASB issued ASU 2025-06, "Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software," which is intended to increase the operability of the recognition guidance considering different methods of software development. The amendments remove all references to prescriptive and sequential software development stages (referred to as “project stages”) throughout Subtopic 350-40, and instead specify an entity is required to start capitalizing software costs when both of the following occur: (1) management has authorized and committed to funding the software project and (2) it is probable that the project will be completed and the software will be used to perform the function intended (referred to as the “probable-to complete recognition threshold”). The Company expects to adopt the new guidance as required for fiscal 2029 and is evaluating the impact the new standard will have on its consolidated financial statements.

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

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, 2026, the aggregate amount of the transaction price allocated to remaining performance obligations was approximately $26.3 billion, of which approximately 67% 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 construction contracts, 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 of service contracts with a duration of one year or less and open purchase orders from the indirect third-party sales channel that have a short cycle time (generally 60 days 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 when incurred and amortized to expense over the period of contract performance.

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

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.

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.

Derivatives: Derivatives consist primarily of foreign currency exchange derivatives and are valued under a market approach using publicly available prices, where available, or dealer quotes.

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.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.