Revenue from Contracts with Customers - Remaining Performance Obligations, Branded Postpaid Contracts (Details) $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 637
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	1,400
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 3,200
Minimum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining contract duration (in years)	1 year
Maximum
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining contract duration (in years)	7 years
Total postpaid service revenues
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 1,100
Remaining contract duration (in years)	24 months