v3.25.4
Summary of Significant Accounting Policies - Disaggregation of revenue (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2025
Dec. 31, 2024
Revenue Recognition    
Revenue $ 1,046 $ 1,016
Consumer Revenue, Data    
Revenue Recognition    
Revenue 239 246
Consumer Revenue, Wireless    
Revenue Recognition    
Revenue 143 142
Consumer Revenue, Other    
Revenue Recognition    
Revenue 27 44
Business Revenue, Data    
Revenue Recognition    
Revenue 500 457
Business Revenue, Wireless    
Revenue Recognition    
Revenue 32 40
Business Revenue, Other    
Revenue Recognition    
Revenue 11 11
Lease, grant, and revenue from subsidies    
Revenue Recognition    
Revenue $ 94 $ 76