Sales of Certain Receivables - Sales of EIP Receivables (Details) - USD ($) $ in Millions |
Jun. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Variable Interest Entity [Line Items] | ||
| Other current assets | $ 1,642 | $ 2,496 |
| Other assets | 12,266 | 2,779 |
| EIP Securitization Arrangement | ||
| Variable Interest Entity [Line Items] | ||
| Revolving receivables facility, maximum borrowing capacity | 1,300 | 1,300 |
| Other current assets | 436 | 388 |
| Other assets | 133 | 120 |
| Other long-term liabilities | $ 4 | $ 4 |