Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Sep. 30, 2021	Oct. 31, 2021	Mar. 31, 2021
Cover [Abstract]
Documents Incorporated by Reference [Text Block]	Portions of the definitive Proxy Statement to be delivered to shareholders in connection with the annual general meeting of shareholders to be held on March 9, 2022 are incorporated by reference into Part III.
Document Information [Line Items]
Entity Incorporation, State or Country Code	L2
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Public Float			$ 42.7
Entity Common Stock, Shares Outstanding		704,332,395
Document Type	10-K
Document Annual Report	true
Document Period End Date	Sep. 30, 2021
Entity File Number	001-13836
Entity Registrant Name	JOHNSON CONTROLS INTERNATIONAL PLC
Entity Tax Identification Number	98-0390500
Entity Central Index Key	0000833444
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2021
Amendment Flag	false
Document Transition Report	false
City Area Code	353
Local Phone Number	21-423-5000
Entity Address, Address Line One	One Albert Quay
Entity Address, City or Town	Cork
Entity Address, Country	IE
Entity Address, Postal Zip Code	T12 X8N6
ICFR Auditor Attestation Flag	true
Ordinary Shares, Par Value 0.01 [Domain]
Document Information [Line Items]
Title of 12(b) Security	Ordinary Shares, Par Value $0.01
Trading Symbol	JCI
Security Exchange Name	NYSE
Notes 4.625 Percent Due 2023 [Domain]
Document Information [Line Items]
Title of 12(b) Security	4.625% Notes due 2023
Trading Symbol	JCI23
Security Exchange Name	NYSE
Notes 1.000 Percent Due 2023 [Domain]
Document Information [Line Items]
Title of 12(b) Security	1.000% Senior Notes due 2023
Trading Symbol	JCI23A
Security Exchange Name	NYSE
Notes 3.625 Percent Due 2024 [Domain]
Document Information [Line Items]
Title of 12(b) Security	3.625% Senior Notes due 2024
Trading Symbol	JCI24A
Security Exchange Name	NYSE
Notes 1.375 Percent Due 2025 [Domain]
Document Information [Line Items]
Title of 12(b) Security	1.375% Notes due 2025
Trading Symbol	JCI25A
Security Exchange Name	NYSE
Notes 3.900 Percent Due 2026 [Domain]
Document Information [Line Items]
Title of 12(b) Security	3.900% Notes due 2026
Trading Symbol	JCI26A
Security Exchange Name	NYSE
Notes 0.375 Percent Due 2027 [Domain]
Document Information [Line Items]
Title of 12(b) Security	0.375% Senior Notes due 2027
Trading Symbol	JCI27
Security Exchange Name	NYSE
Notes 1.750 Percent Due 2030 [Domain]
Document Information [Line Items]
Title of 12(b) Security	1.750% Senior Notes due 2030
Trading Symbol	JCI30
Security Exchange Name	NYSE
Sustainability Notes 2.000 Percent Due 2031 [Domain]
Document Information [Line Items]
Title of 12(b) Security	2.000% Sustainability-Linked Senior Notes due 2031
Trading Symbol	JCI31
Security Exchange Name	NYSE
Notes 1.000 Percent Due 2032 [Domain]
Document Information [Line Items]
Title of 12(b) Security	1.000% Senior Notes due 2032
Trading Symbol	JCI32
Security Exchange Name	NYSE
Notes 6.000 Percent Due 2036 [Domain]
Document Information [Line Items]
Title of 12(b) Security	6.000% Notes due 2036
Trading Symbol	JCI36A
Security Exchange Name	NYSE
Notes 5.700 Percent Due 2041 [Domain]
Document Information [Line Items]
Title of 12(b) Security	5.70% Senior Notes due 2041
Trading Symbol	JCI41B
Security Exchange Name	NYSE
Notes 5.250 Percent Due 2041 [Domain]
Document Information [Line Items]
Title of 12(b) Security	5.250% Senior Notes due 2041
Trading Symbol	JCI41C
Security Exchange Name	NYSE
Notes 4.625 Percent Due 2044 [Domain]
Document Information [Line Items]
Title of 12(b) Security	4.625% Senior Notes due 2044
Trading Symbol	JCI44A
Security Exchange Name	NYSE
Notes 5.125 Percent Due 2045 [Domain]
Document Information [Line Items]
Title of 12(b) Security	5.125% Notes due 2045
Trading Symbol	JCI45B
Security Exchange Name	NYSE
Debentures 6.950 Percent Due December 1, 2045 [Domain]
Document Information [Line Items]
Title of 12(b) Security	6.950% Debentures due December 1, 2045
Trading Symbol	JCI45A
Security Exchange Name	NYSE
Notes 4.500 Percent Due 2047 [Domain]
Document Information [Line Items]
Title of 12(b) Security	4.500% Senior Notes due 2047
Trading Symbol	JCI47
Security Exchange Name	NYSE
Notes 4.950 Percent Due 2064 [Domain]
Document Information [Line Items]
Title of 12(b) Security	4.950% Senior Notes due 2064
Trading Symbol	JCI64A
Security Exchange Name	NYSE