Derivative Instruments and Hedging Activities - Presented on a Net Basis (Details) - USD ($)
$ in Millions |
Sep. 30, 2018 |
Sep. 30, 2017 |
| Derivative [Line Items] |
|
|
| Gross amounts recognized in the consolidated balance sheet, Asset |
$ 3
|
|
| Gross amounts recognized in the consolidated balance sheet, Liability |
41
|
|
| Gross amount subject to offset in master netting arrangements not offset in the Consolidated Balance Sheet, Asset |
(3)
|
|
| Gross amount subject to offset in master netting arrangements not offset in the Consolidated Balance Sheet, Liability |
(3)
|
|
| Derivative Asset |
0
|
|
| Derivative Liability |
$ 38
|
|
| Predecessor |
|
|
| Derivative [Line Items] |
|
|
| Gross amounts recognized in the consolidated balance sheet, Asset |
|
$ 0
|
| Gross amounts recognized in the consolidated balance sheet, Liability |
|
0
|
| Gross amount subject to offset in master netting arrangements not offset in the Consolidated Balance Sheet, Asset |
|
0
|
| Gross amount subject to offset in master netting arrangements not offset in the Consolidated Balance Sheet, Liability |
|
0
|
| Derivative Asset |
|
0
|
| Derivative Liability |
|
$ 0
|