Employee Benefits - Additional Information (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | 9 Months Ended | |
|---|---|---|---|---|
Sep. 30, 2021 |
Sep. 30, 2020 |
Jun. 30, 2021 |
Sep. 30, 2020 |
|
| Compensation And Retirement Disclosure [Abstract] | ||||
| Defined contribution savings plan expenses | $ 11 | $ 9 | $ 31 | $ 38 |