Consolidated Statements of Shareholders' Equity Attributable to Johnson Controls Ordinary Shareholders - USD ($) $ in Millions	Total	Cumulative Effect, Period of Adoption, Adjustment	Ordinary Shares	Ordinary Shares Cumulative Effect, Period of Adoption, Adjustment	Capital in excess of par value	Capital in excess of par value Cumulative Effect, Period of Adoption, Adjustment	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Adjustment	Treasury Stock, at Cost	Treasury Stock, at Cost Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Power Solutions	Power Solutions Ordinary Shares	Power Solutions Capital in excess of par value	Power Solutions Retained Earnings	Power Solutions Treasury Stock, at Cost	Power Solutions Accumulated Other Comprehensive Income (Loss)
Beginning balance at Sep. 30, 2018	$ 21,164		$ 10		$ 16,549		$ 6,604		$ (1,053)		$ (946)
Beginning balance (Adoption of ASC 606) at Sep. 30, 2018		$ (45)		$ 0		$ 0		$ (45)		$ 0		$ 0
Beginning balance (Adoption of ASU 2016-01) at Sep. 30, 2018		0		0		0		8		0		(8)
Beginning balance (Adoption of 2016-16) at Sep. 30, 2018		(546)		0		0		(546)		0		0
Comprehensive income (loss)	5,350		0		0		5,674		0		(324)
Cash dividends	$ (887)		0		0		$ (887)		0		0
Cash dividends ordinary, per share	$ 1.04						$ 1.04
Repurchases and retirements of ordinary shares	$ (5,983)		(2)		0		$ 5,981		0		0
Divestiture of Power Solutions													$ 483	$ 0	$ 0	$ 0	$ 0	$ 483
Other, including options exercised	230		0		263		0		(33)		0
Ending balance at Sep. 30, 2019	19,766		8		16,812		4,827		(1,086)		(795)
Comprehensive income (loss)	650		0		0		631		0		19
Cash dividends	$ (780)		0		0		$ (780)		0		0
Cash dividends ordinary, per share	$ 1.04						$ 1.04
Repurchases and retirements of ordinary shares	$ (2,204)		0		0		$ (2,204)		0		0
Change in noncontrolling interest share	(83)		0		(83)		0		0		0
Other, including options exercised	103		0		136		0		(33)		0
Ending balance at Sep. 30, 2020	17,447		8		16,865		2,469		(1,119)		(776)
Ending balance (Adoption of ASC 842) at Sep. 30, 2020		(5)		0		0		(5)		0		0
Ending balance (Accounting Standards Update 2016-13) at Sep. 30, 2020		$ (4)		$ 0		$ 0		$ (4)		$ 0		$ 0
Comprehensive income (loss)	1,979		0		0		1,637		0		342
Cash dividends	$ (771)		0		0		$ (771)		0		0
Cash dividends ordinary, per share	$ 1.07						$ 1.07
Repurchases and retirements of ordinary shares	$ (1,307)		(1)		0		$ (1,306)		0		0
Change in noncontrolling interest share	(8)		0		(8)		0		0		0
Other, including options exercised	226		0		259		0		(33)		0
Ending balance at Sep. 30, 2021	$ 17,562		$ 7		$ 17,116		$ 2,025		$ (1,152)		$ (434)