Receivables and Related Allowance for Credit Losses - Schedule of Equipment Installment Plan Receivables (Details) - USD ($) $ in Millions	Dec. 31, 2025	Aug. 01, 2025	Dec. 31, 2024
Accounts, Notes, Loans and Financing Receivable [Line Items]
EIP receivables, gross	$ 8,626		$ 7,402
Unamortized imputed discount	(566)		(524)
EIP receivables, net of unamortized imputed discount	8,060		6,878
Allowance for credit losses	(380)		(290)
EIP receivables, net of allowance for credit losses and imputed discount	7,680		6,588
Equipment installment plan receivables, net	4,997		4,379
UScellular Wireless Assets Operations
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equipment installment plan receivables, net		$ 891
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	4,997		4,379
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	$ 2,683		$ 2,209

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