Restructuring Costs - Activity Related to Expenses Incurred and Cash Payments Made (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended |
|---|---|---|
Jun. 30, 2021 |
Jun. 30, 2021 |
|
| Restructuring Reserve [Roll Forward] | ||
| Restructuring Reserve, Beginning Balance | $ 163 | |
| Expenses Incurred | $ 48 | 82 |
| Cash Payments | (147) | |
| Adjustments | (20) | |
| Restructuring Reserve, Ending Balance | 78 | 78 |
| Contract termination costs | ||
| Restructuring Reserve [Roll Forward] | ||
| Restructuring Reserve, Beginning Balance | 81 | |
| Expenses Incurred | 3 | 9 |
| Cash Payments | (65) | |
| Adjustments | 0 | |
| Restructuring Reserve, Ending Balance | 25 | 25 |
| Severance costs | ||
| Restructuring Reserve [Roll Forward] | ||
| Restructuring Reserve, Beginning Balance | 52 | |
| Expenses Incurred | 3 | 19 |
| Cash Payments | (53) | |
| Adjustments | (4) | |
| Restructuring Reserve, Ending Balance | 14 | 14 |
| Network decommissioning | ||
| Restructuring Reserve [Roll Forward] | ||
| Restructuring Reserve, Beginning Balance | 30 | |
| Expenses Incurred | 42 | 54 |
| Cash Payments | (29) | |
| Adjustments | (16) | |
| Restructuring Reserve, Ending Balance | $ 39 | $ 39 |