Derivative Instruments - Schedule of Derivative Instruments Classified as Assets (Liabilities) (Details) - USD ($)
$ in Millions |
Sep. 30, 2019 |
Dec. 31, 2018 |
| Derivative [Line Items] |
|
|
| Derivative assets, current |
$ 3
|
$ 14
|
| Derivative assets, noncurrent |
7
|
9
|
| Derivative liabilities, current |
6
|
2
|
| Derivative liabilities, noncurrent |
81
|
31
|
| Designated Derivative Instruments | Interest rate swaps |
|
|
| Derivative [Line Items] |
|
|
| Derivative assets, current |
0
|
0
|
| Derivative assets, noncurrent |
0
|
3
|
| Derivative liabilities, current |
6
|
2
|
| Derivative liabilities, noncurrent |
81
|
25
|
| Not Designated as Hedging Instrument | Interest rate swaps |
|
|
| Derivative [Line Items] |
|
|
| Derivative assets, current |
|
0
|
| Derivative assets, noncurrent |
|
0
|
| Derivative liabilities, current |
|
0
|
| Derivative liabilities, noncurrent |
|
4
|
| Not Designated as Hedging Instrument | Energy derivative |
|
|
| Derivative [Line Items] |
|
|
| Derivative assets, current |
|
7
|
| Derivative assets, noncurrent |
|
0
|
| Derivative liabilities, current |
|
0
|
| Derivative liabilities, noncurrent |
|
0
|
| Not Designated as Hedging Instrument | Foreign currency forward contracts |
|
|
| Derivative [Line Items] |
|
|
| Derivative assets, current |
3
|
6
|
| Derivative assets, noncurrent |
7
|
6
|
| Derivative liabilities, current |
0
|
0
|
| Derivative liabilities, noncurrent |
0
|
2
|
| Not Designated as Hedging Instrument | Congestion revenue rights |
|
|
| Derivative [Line Items] |
|
|
| Derivative assets, current |
0
|
1
|
| Derivative assets, noncurrent |
0
|
0
|
| Derivative liabilities, current |
0
|
0
|
| Derivative liabilities, noncurrent |
0
|
$ 0
|
| Derivative asset (less than $1 million for congestion revenue rights in September 30, 2019) |
$ 1
|
|