v3.26.1
Restructuring Costs - Schedule of Activity Related to Reduction Initiative Expenses Incurred (Details) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2026
Restructuring Reserve [Roll Forward]    
Expenses Incurred   $ 175
UScellular Acquisition Restructuring Initiatives    
Restructuring Reserve [Roll Forward]    
Restructuring reserve, beginning balance   91
Expenses Incurred $ 90 175
Cash Payments   (108)
Restructuring reserve, ending balance 158 158
Network Optimization Restructuring Initiatives    
Restructuring Reserve [Roll Forward]    
Restructuring reserve, beginning balance   1
Expenses Incurred 36 101
Cash Payments   (44)
Adjustments for Non-Cash Items   (8)
Restructuring reserve, ending balance 50 50
Contract termination costs    
Restructuring Reserve [Roll Forward]    
Expenses Incurred   92
Contract termination costs | UScellular Acquisition Restructuring Initiatives    
Restructuring Reserve [Roll Forward]    
Restructuring reserve, beginning balance   31
Expenses Incurred 51 92
Cash Payments   (45)
Restructuring reserve, ending balance 78 78
Contract termination costs | Network Optimization Restructuring Initiatives    
Restructuring Reserve [Roll Forward]    
Restructuring reserve, beginning balance   0
Expenses Incurred 13 40
Cash Payments   (27)
Adjustments for Non-Cash Items   0
Restructuring reserve, ending balance 13 13
Severance costs    
Restructuring Reserve [Roll Forward]    
Expenses Incurred   57
Severance costs | UScellular Acquisition Restructuring Initiatives    
Restructuring Reserve [Roll Forward]    
Restructuring reserve, beginning balance   59
Expenses Incurred 31 57
Cash Payments   (39)
Restructuring reserve, ending balance 77 77
Network decommissioning    
Restructuring Reserve [Roll Forward]    
Expenses Incurred   26
Network decommissioning | UScellular Acquisition Restructuring Initiatives    
Restructuring Reserve [Roll Forward]    
Restructuring reserve, beginning balance   1
Expenses Incurred 8 26
Cash Payments   (24)
Restructuring reserve, ending balance 3 3
Network decommissioning | Network Optimization Restructuring Initiatives    
Restructuring Reserve [Roll Forward]    
Restructuring reserve, beginning balance   1
Expenses Incurred 23 61
Cash Payments   (17)
Adjustments for Non-Cash Items   (8)
Restructuring reserve, ending balance $ 37 $ 37