Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (122)	$ 4,276	$ 305	$ 5,233
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	76	(94)	(157)	(95)
Realized and unrealized gains (losses) on derivatives	6	(9)	3	10
Pension and postretirement plans	0	0	(1)	0
Other comprehensive income (loss)	82	(103)	(155)	(85)
Total comprehensive income (loss)	(40)	4,173	150	5,148
Comprehensive income attributable to noncontrolling interests	64	76	108	179
Comprehensive income (loss) attributable to Johnson Controls	$ (104)	$ 4,097	$ 42	$ 4,969