Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 1,819	$ (652)	$ 1,679
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	103	(94)	(825)
Realized and unrealized gains (losses) on derivatives	(14)	9	(10)
Realized and unrealized gains (losses) on marketable securities	5	(1)	0
Pension and postretirement plans	0	(1)	(10)
Other comprehensive income (loss)	94	(87)	(845)
Total comprehensive income (loss)	1,913	(739)	834
Comprehensive income attributable to noncontrolling interests	203	225	91
Comprehensive income (loss) attributable to Johnson Controls	$ 1,710	$ (964)	$ 743