Sales of Certain Receivables - Sales of EIP Receivables (Details) - USD ($) |
Jun. 30, 2020 |
Dec. 31, 2019 |
Dec. 31, 2015 |
|---|---|---|---|
| Variable Interest Entity [Line Items] | |||
| Other current assets | $ 2,586,000,000 | $ 1,972,000,000 | |
| Other assets | 2,326,000,000 | 1,891,000,000 | |
| EIP Securitization Arrangement | |||
| Variable Interest Entity [Line Items] | |||
| Revolving receivables facility, maximum borrowing capacity | 1,300,000,000 | 1,300,000,000 | $ 1,300,000,000 |
| Other current assets | 383,000,000 | 344,000,000 | |
| Other assets | 107,000,000 | 89,000,000 | |
| Other long-term liabilities | $ 3,000,000 | $ 18,000,000 |