Equipment Installment Plans - Gross Receivables by Credit Category (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	$ 1,151	$ 1,211
2021	52
2022	439
2023	660
Unbilled \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	1,085	1,141
Billed \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	43	48
Billed \| Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	23	22
Lowest Risk
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	1,024	1,070
2021	49
2022	404
2023	571
Lowest Risk \| Unbilled \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	977	1,016
Lowest Risk \| Billed \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	35	41
Lowest Risk \| Billed \| Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	12	13
Lower Risk
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	100	109
2021	3
2022	30
2023	67
Lower Risk \| Unbilled \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	88	98
Lower Risk \| Billed \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	5	5
Lower Risk \| Billed \| Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	7	6
Slight Risk
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	21	26
2021	0
2022	4
2023	17
Slight Risk \| Unbilled \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	16	22
Slight Risk \| Billed \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	2	2
Slight Risk \| Billed \| Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	3	2
Higher Risk
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	6	6
2021	0
2022	1
2023	5
Higher Risk \| Unbilled \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	4	5
Higher Risk \| Billed \| Current
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	1	0
Higher Risk \| Billed \| Past Due
Financing Receivable, Credit Quality Indicator [Line Items]
Equipment installment plan receivables, gross	$ 1	$ 1

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