v3.20.4

Sales Of Receivables (Equipment Installment and AT&T Revolving Programs) (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019
Equipment Installment Program | Guarantee Obligation |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Guarantee obligation | $ 228 | $ 384
Equipment Installment Program | Accounts payable and accrued liabilities | Guarantee Obligation |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Guarantee obligation | 161 | 148
Equipment Installment Program | Deferred Purchase Price Receivables |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Deferred purchase price receivable | 1,991 | 2,336
Equipment Installment Program | Deferred Purchase Price Receivables | Other current assets |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Deferred purchase price receivable | 1,476 | $ 1,569
Revolving Receivables Program |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Revolving agreement, term |  | 1 year
Revolving agreement, transfer amount (up to) | $ 5,300 | $ 4,300
Revolving agreement extension term | 1 year |
Receivables pledged as collateral | $ 3,909 |

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