Other Financial Data - Summary of Components of Fixed Assets, Net (Details) - USD ($) $ in Millions |
Sep. 30, 2021 |
Dec. 31, 2020 |
|---|---|---|
| Property Plant And Equipment [Line Items] | ||
| Total Fixed assets, gross | $ 233 | $ 546 |
| Less: Accumulated depreciation | 14 | 212 |
| Fixed assets, net | 219 | 334 |
| Capitalized Software | ||
| Property Plant And Equipment [Line Items] | ||
| Total Fixed assets, gross | 40 | 242 |
| Leasehold Improvements | ||
| Property Plant And Equipment [Line Items] | ||
| Total Fixed assets, gross | 39 | 63 |
| Computer Equipment | ||
| Property Plant And Equipment [Line Items] | ||
| Total Fixed assets, gross | 98 | 192 |
| Furniture, Fixtures and Equipment | ||
| Property Plant And Equipment [Line Items] | ||
| Total Fixed assets, gross | 12 | 21 |
| Construction in Progress | ||
| Property Plant And Equipment [Line Items] | ||
| Total Fixed assets, gross | $ 44 | $ 28 |