Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 483	$ (115)	$ 754	$ 263
Other comprehensive income (loss), net of tax
Foreign currency translation adjustments	204	252	283	(451)
Realized and unrealized gains (losses) on derivatives	(10)	(8)	(11)	(4)
Realized and unrealized gains (losses) on marketable securities	(2)	11	(2)	9
Other comprehensive income (loss)	192	255	270	(446)
Total comprehensive income (loss)	675	140	1,024	(183)
Comprehensive income attributable to noncontrolling interests	77	42	137	51
Comprehensive income (loss) attributable to Johnson Controls	$ 598	$ 98	$ 887	$ (234)