Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 1,870	$ 795	$ 5,887
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	376	25	(342)
Realized and unrealized gains (losses) on derivatives	(18)	8	6
Pension and postretirement plans	4	8	(6)
Other comprehensive income (loss)	362	41	(342)
Total comprehensive income	2,232	836	5,545
Comprehensive income attributable to noncontrolling interests	253	186	195
Comprehensive income attributable to Johnson Controls	$ 1,979	$ 650	$ 5,350