Derivative Instruments and Hedging Activities (Policies)	9 Months Ended
	Jun. 30, 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 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 the AOCI account within shareholders’ equity attributable to Johnson Controls ordinary shareholders where they offset currency gains and losses recorded on its net investments globally.The Company also holds certain foreign currency forward and option contracts not designated as hedging instruments under ASC 815. The change in fair value of these foreign currency exchange derivatives are recorded in the consolidated statements of income in the period in which they occur.The Company has not elected to offset the fair value positions of the derivative contracts recorded in the consolidated statements of financial position.