Derivative Instruments and Hedging Activities (Policies)	3 Months Ended
	Dec. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives, Policy	As cash flow hedges under ASC 815, "Derivatives and Hedging," the 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 also 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 Company has not elected to offset the fair value positions of the derivative contracts recorded in the consolidated statements of financial position.