Restructuring Costs - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
UScellular Acquisition Restructuring Initiatives
Restructuring Cost and Reserve [Line Items]
Amortization of the right-of-use assets on lease contracts	$ 10	$ 0	$ 321	$ 0
Total restructuring plan expenses	39		214
UScellular Acquisition Restructuring Initiatives \| Network decommissioning
Restructuring Cost and Reserve [Line Items]
Restructuring and related cost, accelerated depreciation	0	$ 0	242	$ 0
Total restructuring plan expenses	11		37
Network Optimization Restructuring Initiatives
Restructuring Cost and Reserve [Line Items]
Total restructuring plan expenses	30		131
Network Optimization Restructuring Initiatives \| Network decommissioning
Restructuring Cost and Reserve [Line Items]
Total restructuring plan expenses	21		82
Retail Initiatives
Restructuring Cost and Reserve [Line Items]
Total restructuring plan expenses	31		133
Liabilities associated with retail initiatives	$ 40		$ 40

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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