Equity and Noncontrolling Interests Equity Attributable to Johnson Controls and Noncontrolling Interests (Additional Information) (Details) - USD ($) $ in Millions |
12 Months Ended | |||
---|---|---|---|---|
Sep. 30, 2020 |
Sep. 30, 2019 |
Sep. 30, 2018 |
Mar. 31, 2019 |
|
Equity, Class of Treasury Stock [Line Items] | ||||
Stock repurchase program, authorized amount | $ 8,500 | |||
Stock Repurchase Program, Remaining Authorized Repurchase Amount | $ 2,400 | |||
Stock Repurchased and Retired During Period, Value | 2,204 | |||
Repurchases of ordinary shares | $ 5,983 | $ 300 | ||
Stock Repurchased and Retired During Period Value Tender Offer | 4,035 | |||
Stock Repurchased and Retired During Period Value Open Market | 1,948 | |||
Parent | ||||
Equity, Class of Treasury Stock [Line Items] | ||||
Repurchases of ordinary shares | 2,204 | 5,983 | 300 | |
Stockholders' Equity, Total | ||||
Equity, Class of Treasury Stock [Line Items] | ||||
Repurchases of ordinary shares | $ 2,204 | $ 5,983 | $ 300 |