Receivables and Related Allowance for Credit Losses - Schedule of Equipment Installment Plan Receivables (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
EIP receivables, gross	$ 8,453	$ 8,626
Unamortized imputed discount	(560)	(566)
EIP receivables, net of unamortized imputed discount	7,893	8,060
Allowance for credit losses	(405)	(380)
EIP receivables, net of allowance for credit losses and imputed discount	7,488	7,680
Equipment installment plan receivables, net of allowance for credit losses and imputed discount
Accounts, Notes, Loans and Financing Receivable [Line Items]
EIP receivables, net of allowance for credit losses and imputed discount	4,935	4,997
Equipment installment plan receivables due after one year, net of allowance for credit losses and imputed discount
Accounts, Notes, Loans and Financing Receivable [Line Items]
EIP receivables, net of allowance for credit losses and imputed discount	$ 2,553	$ 2,683

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

Amortized cost, before allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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