v3.25.4
Restructuring Costs - Schedule of Restructuring Plan Expenses Incurred (Details) - USD ($)
$ in Millions
 5 Months Ended 12 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2024
Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]        
Restructuring Incurred Cost Statement Of Income Or Comprehensive Income Extensible Enumeration Not Disclosed Flag   Total restructuring plan expenses    
UScellular Acquisition Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses $ 111 $ 111    
Network Optimization Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses   69    
Sprint Merger Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses     $ 95 $ 337
Incurred to Date 2,903 2,903    
Contract termination costs | UScellular Acquisition Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses 32 32    
Contract termination costs | Network Optimization Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses   5    
Contract termination costs | Sprint Merger Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses     4 45
Incurred to Date 472 472    
Severance costs | UScellular Acquisition Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses 63 63    
Severance costs | Sprint Merger Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses     0 3
Incurred to Date 574 574    
Severance costs | 2023 Workforce Reduction        
Restructuring Cost and Reserve [Line Items]        
Restructuring expenses   (3) (5) 462
Incurred to Date 454 454    
Network decommissioning | UScellular Acquisition Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses 16 16    
Network decommissioning | Network Optimization Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses   64    
Network decommissioning | Sprint Merger Restructuring Initiatives        
Restructuring Cost and Reserve [Line Items]        
Total restructuring plan expenses     $ 91 $ 289
Incurred to Date $ 1,857 $ 1,857