Short-Term Debt - Credit Facility - Additional Information (Details) |
12 Months Ended |
|---|---|
Dec. 31, 2019 | |
| Short-term Debt [Line Items] | |
| Line of credit facility consolidated debt to consolidated capitalization ratio, required | 0.70 |
| Line of credit facility consolidated debt to consolidated capitalization ratio | 0.61 |
| Minimum | |
| Short-term Debt [Line Items] | |
| Line of credit facility consolidated debt to consolidated capitalization ratio | 0.61 |
| Debt, no collateral, prepaid period | 2 months |
| Maximum | |
| Short-term Debt [Line Items] | |
| Debt, no collateral, prepaid period | 3 months |