Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Mar. 31, 2020 |
Jun. 30, 2019 |
Jun. 30, 2020 |
Jun. 30, 2019 |
|
| Accounting Policies [Abstract] | ||||
| Interest costs capitalized | $ 3 | $ 1 | $ 5 | $ 8 |