Equity and Noncontrolling Interests - Equity Attributable to Johnson Controls and Noncontrolling Interests (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2015
Equity [Line Items]
Noncontrolling interest acquired					$ 679
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 24,118
Beginning balance			972
Beginning balance			25,090
Net income attributable to Johnson Controls	$ 555	$ 383	736	$ 303
Foreign currency translation adjustments	285	(141)	(166)	(115)
Realized and unrealized gains (losses) on derivatives	(9)	4	(13)	6
Realized and unrealized gains (losses) on marketable securities	(3)	0	6	0
Other comprehensive income (loss)	273	(137)	(173)	(109)
Comprehensive income attributable to Johnson Controls	813	248	579	186
Comprehensive income attributable to noncontrolling interests	89	74	140	185
Total comprehensive income	902	322	719	371
Repurchase of ordinary shares	(307)	(475)	(426)	(475)
Ending balance	19,731		19,731
Ending balance	884		884
Ending balance	20,615		20,615
Equity Attributable to Johnson Controls
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	19,388	9,984	24,118	10,376
Net income attributable to Johnson Controls	555	383	736	303
Foreign currency translation adjustments		(141)		(126)
Realized and unrealized gains (losses) on derivatives		6		9
Realized and unrealized gains (losses) on marketable securities		0		0
Other comprehensive income (loss)	258	(135)	(157)	(117)
Comprehensive income attributable to Johnson Controls	813	248	579	186
Cash dividends - ordinary shares	(234)	(189)	(705)	(566)
Dividends attributable to noncontrolling interests	0	0	0	0
Repurchase of ordinary shares	(307)	(475)	(426)	(475)
Change In noncontrolling interest share	0	0	0	0
Spin-off of Adient			(4,038)	0
Other, including options exercised	71	31	203	78
Ending balance	19,731	9,599	19,731	9,599
Equity Attributable to Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	813	898	972	163
Income attributable to noncontrolling interests	66	59	127	129
Foreign currency translation adjustments	3	3	(22)	12
Realized and unrealized gains (losses) on derivatives	(1)	(2)	1	(1)
Realized and unrealized gains (losses) on marketable securities	0	0	0	0
Other comprehensive income (loss)	2	1	(21)	11
Comprehensive income attributable to noncontrolling interests	68	60	106	140
Cash dividends - ordinary shares	0	0	0	0
Dividends attributable to noncontrolling interests	0	(35)	(47)	(71)
Repurchase of ordinary shares	0	0	0	0
Change In noncontrolling interest share	3	1	(9)	692
Spin-off of Adient			(138)	0
Other, including options exercised	0	0	0	0
Ending balance	884	924	884	924
Total Equity Excluding Redeemable Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance	20,201	10,882	25,090	10,539
Net income	621	442	863	432
Foreign currency translation adjustments	271	(138)	(172)	(114)
Realized and unrealized gains (losses) on derivatives	(8)	4	(12)	8
Realized and unrealized gains (losses) on marketable securities	(3)	0	6	0
Other comprehensive income (loss)	260	(134)	(178)	(106)
Total comprehensive income	881	308	685	326
Cash dividends - ordinary shares	(234)	(189)	(705)	(566)
Dividends attributable to noncontrolling interests	0	(35)	(47)	(71)
Repurchase of ordinary shares	(307)	(475)	(426)	(475)
Change In noncontrolling interest share	3	1	(9)	692
Spin-off of Adient			(4,176)	0
Other, including options exercised	71	31	203	78
Ending balance	20,615	$ 10,523	20,615	$ 10,523
Parent Company [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			24,118
Beginning balance			0
Beginning balance			24,118
Net income attributable to Johnson Controls	555		736
Foreign currency translation adjustments	268		(150)
Realized and unrealized gains (losses) on derivatives	(7)		(13)
Realized and unrealized gains (losses) on marketable securities	(3)		6
Other comprehensive income (loss)	258		(157)
Comprehensive income attributable to Johnson Controls	813		579
Comprehensive income attributable to noncontrolling interests	0		0
Total comprehensive income	813		579
Ending balance	19,731		19,731
Ending balance	0		0
Ending balance	$ 19,731		$ 19,731