v3.25.4
Restructuring Costs - Schedule of Activity Related to Reduction Initiative Expenses Incurred (Details) - USD ($)
$ in Millions
 5 Months Ended 12 Months Ended
Dec. 31, 2025
Dec. 31, 2025
UScellular Acquisition Restructuring Initiatives    
Restructuring Cost and Reserve [Line Items]    
Restructuring reserve, beginning balance $ 0  
Expenses Incurred 111 $ 111
Cash Payments (12)  
Adjustments for Non-Cash Items (8)  
Restructuring reserve, ending balance 91 91
Network Optimization Restructuring Initiatives    
Restructuring Cost and Reserve [Line Items]    
Restructuring reserve, beginning balance   0
Expenses Incurred   69
Cash Payments   (10)
Adjustments for Non-Cash Items   (58)
Restructuring reserve, ending balance 1 1
Contract termination costs | UScellular Acquisition Restructuring Initiatives    
Restructuring Cost and Reserve [Line Items]    
Restructuring reserve, beginning balance 0  
Expenses Incurred 32 32
Cash Payments (1)  
Adjustments for Non-Cash Items 0  
Restructuring reserve, ending balance 31 31
Contract termination costs | Network Optimization Restructuring Initiatives    
Restructuring Cost and Reserve [Line Items]    
Restructuring reserve, beginning balance   0
Expenses Incurred   5
Cash Payments   (5)
Adjustments for Non-Cash Items   0
Restructuring reserve, ending balance 0 0
Severance costs | UScellular Acquisition Restructuring Initiatives    
Restructuring Cost and Reserve [Line Items]    
Restructuring reserve, beginning balance 0  
Expenses Incurred 63 63
Cash Payments (4)  
Adjustments for Non-Cash Items 0  
Restructuring reserve, ending balance 59 59
Network decommissioning | UScellular Acquisition Restructuring Initiatives    
Restructuring Cost and Reserve [Line Items]    
Restructuring reserve, beginning balance 0  
Expenses Incurred 16 16
Cash Payments (7)  
Adjustments for Non-Cash Items (8)  
Restructuring reserve, ending balance 1 1
Network decommissioning | Network Optimization Restructuring Initiatives    
Restructuring Cost and Reserve [Line Items]    
Restructuring reserve, beginning balance   0
Expenses Incurred   64
Cash Payments   (5)
Adjustments for Non-Cash Items   (58)
Restructuring reserve, ending balance $ 1 $ 1