Goodwill and Other Intangible Assets - Intangible Assets - Cost (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2018 |
Dec. 31, 2019 |
|
| Finite-lived Intangible Assets [Roll Forward] | ||
| Finite-lived intangible assets, net, beginning | $ 99 | |
| Disposals, finite-lived | $ (4) | (8) |
| Finite-lived intangible assets, net, ending | 91 | |
| Customer relationships | ||
| Finite-lived Intangible Assets [Roll Forward] | ||
| Finite-lived intangible assets, net, beginning | 86 | |
| Disposals, finite-lived | (8) | |
| Finite-lived intangible assets, net, ending | 78 | |
| Other intangible assets | ||
| Finite-lived Intangible Assets [Roll Forward] | ||
| Finite-lived intangible assets, net, beginning | 13 | |
| Disposals, finite-lived | 0 | |
| Finite-lived intangible assets, net, ending | $ 13 |