v3.26.1
Goodwill and Other Intangible Assets - Changes in Carrying Amount of Goodwill (Details) - USD ($)
$ in Millions
 9 Months Ended
Jun. 30, 2026
Sep. 30, 2025
Goodwill [Line Items]    
Goodwill   $ 17,828
Accumulated impairment loss   (1,195)
Goodwill [Roll Forward]    
Balance at beginning of period $ 16,633  
Acquisitions 196  
Foreign currency translation and other (217)  
Balance at end of period 16,612  
Disposal Group, Disposed of by Sale, Not Discontinued Operations | ADT Spain Security Business    
Goodwill [Roll Forward]    
Goodwill transfer, out of 38  
Discontinued Operations, Disposed of by Sale | ADT United Kingdom Residential Security Business    
Goodwill [Roll Forward]    
Goodwill transfer, out of 102  
Americas    
Goodwill [Line Items]    
Goodwill   14,092
Accumulated impairment loss   (918)
Goodwill [Roll Forward]    
Balance at beginning of period 13,174  
Acquisitions 193  
Foreign currency translation and other (30)  
Balance at end of period 13,337  
EMEA    
Goodwill [Line Items]    
Goodwill   2,388
Accumulated impairment loss   (277)
Goodwill [Roll Forward]    
Balance at beginning of period 2,111  
Acquisitions 3  
Foreign currency translation and other (188)  
Balance at end of period 1,926  
APAC    
Goodwill [Line Items]    
Goodwill   1,348
Accumulated impairment loss   $ 0
Goodwill [Roll Forward]    
Balance at beginning of period 1,348  
Acquisitions 0  
Foreign currency translation and other 1  
Balance at end of period $ 1,349