Commitments and Contingencies - Future Minimum Lease Payments, Operating Leases (Details) $ in Millions |
Sep. 30, 2018
USD ($)
|
|---|---|
| Commitments and Contingencies Disclosure [Abstract] | |
| 2019 | $ 48 |
| 2020 | 40 |
| 2021 | 28 |
| 2022 | 24 |
| 2023 | 15 |
| 2024 and thereafter | 39 |
| Future minimum lease payments | $ 194 |