Equity and Noncontrolling Interests Equity Attributable to Johnson Controls and Noncontrolling Interests (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Equity [Line Items]
Payments for Repurchase of Common Stock	$ 651	$ 501	$ 1,362
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	24,118	10,335	11,270
Beginning balance	972
Beginning balance	25,090
Net income (loss)	1,611	(868)	1,563
Foreign currency translation adjustments	103	(94)	(825)
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)
Comprehensive income (loss) attributable to Johnson Controls	1,710	(964)	743
Comprehensive income attributable to noncontrolling interest	203	225	91
Total comprehensive income (loss)	1,913	(739)	834
Result of contribution of Johnson Controls, Inc. to Johnson Controls International plc	15,800	15,808
Cash dividends - common stock	(938)	(752)	(681)
Repurchases of common stock	651	501	1,362
Change in noncontrolling interest share	8
Spin-off of Adient	4,038
Other, including options exercised	(246)	(192)	(365)
Ending balance	20,447	24,118	10,335
Ending balance	920	972
Ending balance	21,367	25,090
Parent
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	24,118	10,335	11,270
Net income (loss)	1,611	(868)	1,563
Foreign currency translation adjustments	108	(105)	(799)
Realized and unrealized gains (losses) on derivatives	(14)	11	(11)
Realized and unrealized gains (losses) on marketable securities	5	(1)
Pension and postretirement plans		(1)	(10)
Other comprehensive income (loss)	99	(96)	(820)
Comprehensive income (loss) attributable to Johnson Controls	1,710	(964)	743
Result of contribution of Johnson Controls, Inc. to Johnson Controls International plc		15,808
Cash dividends - common stock	(938)	(752)	(681)
Dividends attributable to noncontrolling interests	0	0	0
Repurchases of common stock	(651)	(501)	(1,362)
Change in noncontrolling interest share	0	0	0
Spin-off of Adient	(4,038)
Other, including options exercised	246	192	365
Ending balance	20,447	24,118	10,335
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Spin-off of Adient	(138)
Nonredeemable Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	972	163	251
Income from continuing operations attributable to noncontrolling interests	164	168	65
Foreign currency translation adjustments	(18)	9	(3)
Realized and unrealized gains (losses) on derivatives	1	(1)	0
Realized and unrealized gains (losses) on marketable securities	0	0
Pension and postretirement plans		0	0
Other comprehensive income (loss)	(17)	8	(3)
Comprehensive income attributable to noncontrolling interest	147	176	62
Result of contribution of Johnson Controls, Inc. to Johnson Controls International plc		0
Cash dividends - common stock	0	0	0
Dividends attributable to noncontrolling interests	(56)	(93)	(57)
Repurchases of common stock	0	0	0
Change in noncontrolling interest share	(5)	726	(93)
Other, including options exercised	0	0	0
Ending balance	920	972	163
Stockholders' Equity, Total
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	25,090	10,498	11,521
Net Income (loss)	1,775	(700)	1,628
Foreign currency translation adjustments	90	(96)	(802)
Realized and unrealized gains (losses) on derivatives	(13)	10	(11)
Realized and unrealized gains (losses) on marketable securities	5	(1)
Pension and postretirement plans		(1)	(10)
Other comprehensive income (loss)	82	(88)	(823)
Total comprehensive income (loss)	1,857	(788)	805
Result of contribution of Johnson Controls, Inc. to Johnson Controls International plc		15,808
Cash dividends - common stock	(938)	(752)	(681)
Dividends attributable to noncontrolling interests	(56)	(93)	(57)
Repurchases of common stock	(651)	(501)	(1,362)
Change in noncontrolling interest share	(5)	726	(93)
Spin-off of Adient	(4,176)
Other, including options exercised	246	192	365
Ending balance	$ 21,367	$ 25,090	$ 10,498