Operations and Significant Accounting Policies - Revenue - Nature of Revenue Streams (Continued) (Details) - Long-term Contract with Customer [Member] - Regulated Operations [Member]
$ in Millions |
Dec. 31, 2019
USD ($)
|
| Other Power Supplier Customers [Member] | Industrial [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Amount |
$ 55
|
| Other Power Supplier Customers [Member] | Other Power Suppliers [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Amount |
$ 3
|
| Other Power Supplier Customers [Member] | Other Power Suppliers [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period |
1 year
|
| Industrial Customers [Member] | Industrial [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period |
1 year
|
| Industrial Customers [Member] | Industrial [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period |
1 year
|
| Industrial Customers [Member] | Industrial [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period |
1 year
|
| Revenue, Remaining Performance Obligation, Amount |
$ 55
|
| Industrial Customers [Member] | Industrial [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period |
1 year
|
| Revenue, Remaining Performance Obligation, Amount |
$ 55
|
| Industrial Customers [Member] | Industrial [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period |
1 year
|
| Revenue, Remaining Performance Obligation, Amount |
$ 55
|
| Industrial Customers [Member] | Industrial [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01 |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] |
|
| Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period |
5 years
|
| Revenue, Remaining Performance Obligation, Amount |
$ 65
|