TIFSA Condensed Income Statement (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017
Condensed Income Statements, Captions [Line Items]
Net sales	$ 7,475		$ 7,267		$ 14,910	$ 14,353
Cost of sales	5,255		4,986		10,521	9,958
Gross profit	2,220		2,281		4,389	4,395
Selling, general and administrative expenses	(1,588)		(1,726)		(3,005)	(3,296)
Restructuring and impairment costs	0	$ (158)	(99)	$ (78)	(158)	(177)
Net Financing Charges	(115)		(116)		(231)	(252)
Equity income (loss)	44		53		104	108
Intercompany interest and fees	0		0		0	0
Income (loss) from continuing operations before income taxes	561		393		1,099	778
Income tax provision	78		508		345	481
Income (loss) from continuing operations	483		(115)		754	297
Income (loss) from sale of intercompany investment, net of tax	0				0	0
Loss from discontinued operations, net of tax	0		0		0	(34)
Net income (loss)	483		(115)		754	263
Income from continuing operations attributable to noncontrolling interests	45		33		86	73
Income from discontinued operations attributable to noncontrolling interests	0		0		0	9
Net income attributable to Johnson Controls	438		(148)		668	181
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	0		0		0	0
Cost of sales	0		0		0	0
Gross profit	0		0		0	0
Selling, general and administrative expenses	0		0		0	0
Restructuring and impairment costs			0		0	0
Net Financing Charges	0		0		0	0
Equity income (loss)	(1,012)		672		(1,627)	750
Intercompany interest and fees	0		0		0	0
Income (loss) from continuing operations before income taxes	(1,012)		672		(1,627)	750
Income tax provision	0		0		0	0
Income (loss) from continuing operations	(1,012)				(1,627)	750
Income (loss) from sale of intercompany investment, net of tax	953				953	935
Loss from discontinued operations, net of tax						0
Net income (loss)	(59)		672		(674)	1,685
Income from continuing operations attributable to noncontrolling interests	0		0		0	0
Income from discontinued operations attributable to noncontrolling interests						0
Net income attributable to Johnson Controls	(59)		672		(674)	1,685
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	0		0		0	0
Cost of sales	0		0		0	0
Gross profit	0		0		0	0
Selling, general and administrative expenses	(7)		(4)		(10)	(6)
Restructuring and impairment costs			0		0	0
Net Financing Charges	(86)		(59)		(136)	(78)
Equity income (loss)	582		(103)		867	215
Intercompany interest and fees	(51)		18		(53)	50
Income (loss) from continuing operations before income taxes	438		(148)		668	181
Income tax provision	0		0		0	0
Income (loss) from continuing operations	438				668	181
Income (loss) from sale of intercompany investment, net of tax	0				0	0
Loss from discontinued operations, net of tax						0
Net income (loss)	438		(148)		668	181
Income from continuing operations attributable to noncontrolling interests	0		0		0	0
Income from discontinued operations attributable to noncontrolling interests						0
Net income attributable to Johnson Controls	438		(148)		668	181
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	0		0		0	0
Cost of sales	0		0		0	0
Gross profit	0		0		0	0
Selling, general and administrative expenses	0		0		0	0
Restructuring and impairment costs			0		0	0
Net Financing Charges	23		0		24	0
Equity income (loss)	439		(187)		627	(473)
Intercompany interest and fees	70		73		155	73
Income (loss) from continuing operations before income taxes	532		(114)		806	(400)
Income tax provision	0		0		0	0
Income (loss) from continuing operations	532				806	(400)
Income (loss) from sale of intercompany investment, net of tax	0				0	0
Loss from discontinued operations, net of tax						0
Net income (loss)	532		(114)		806	(400)
Income from continuing operations attributable to noncontrolling interests	0		0		0	0
Income from discontinued operations attributable to noncontrolling interests						0
Net income attributable to Johnson Controls	532		(114)		806	(400)
Subsidiary Issuer [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	0		0		0	0
Cost of sales	0		0		0	0
Gross profit	0		0		0	0
Selling, general and administrative expenses	11		(1)		11	0
Restructuring and impairment costs			0		0	0
Net Financing Charges	(3)		5		(5)	(14)
Equity income (loss)	(9)		(382)		133	(492)
Intercompany interest and fees	(17)		20		(46)	37
Income (loss) from continuing operations before income taxes	(18)		(358)		93	(469)
Income tax provision	0		0		0	0
Income (loss) from continuing operations	(18)				93	(469)
Income (loss) from sale of intercompany investment, net of tax	0				0	(935)
Loss from discontinued operations, net of tax						0
Net income (loss)	(18)		(358)		93	(1,404)
Income from continuing operations attributable to noncontrolling interests	0		0		0	0
Income from discontinued operations attributable to noncontrolling interests						0
Net income attributable to Johnson Controls	(18)		(358)		93	(1,404)
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Net sales	7,475		7,267		14,910	14,353
Cost of sales	5,255		4,986		10,521	9,958
Gross profit	2,220		2,281		4,389	4,395
Selling, general and administrative expenses	(1,592)		(1,721)		(3,006)	(3,290)
Restructuring and impairment costs			(99)		(158)	(177)
Net Financing Charges	(49)		(62)		(114)	(160)
Equity income (loss)	44		53		104	108
Intercompany interest and fees	(2)		(111)		(56)	(160)
Income (loss) from continuing operations before income taxes	621		341		1,159	716
Income tax provision	78		508		345	481
Income (loss) from continuing operations	543				814	235
Income (loss) from sale of intercompany investment, net of tax	(953)				(953)	0
Loss from discontinued operations, net of tax						(34)
Net income (loss)	(410)		(167)		(139)	201
Income from continuing operations attributable to noncontrolling interests	45		33		86	73
Income from discontinued operations attributable to noncontrolling interests						9
Net income attributable to Johnson Controls	$ (455)		$ (200)		$ (225)	$ 119