Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions |
2 Months Ended | 10 Months Ended | 12 Months Ended |
|---|---|---|---|
Dec. 15, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
|
| Statement of Comprehensive Income [Abstract] | |||
| Pension, post-retirement and postemployment benefit-related items, tax | $ (58) | $ (19) | $ (19) |
| Change in interest rate swaps, tax | $ 1 |