Borrowings and Other Financing Instruments Term Loan (Details) - USD ($) |
9 Months Ended | ||||
|---|---|---|---|---|---|
Sep. 30, 2020 |
Sep. 30, 2019 |
Mar. 23, 2020 |
Dec. 31, 2019 |
Dec. 20, 2019 |
|
| Short-term Debt [Line Items] | |||||
| Amount outstanding at period end | $ 500,000,000 | $ 595,000,000 | |||
| Proceeds from issuance of common stock | 5,000,000 | $ 457,000,000 | |||
| Expiration Period, Line of Credit | $ 364 | $ 364 | |||
| 364-Day Term Loan [Member] | Short-term Debt [Member] | Xcel Energy Inc. | |||||
| Short-term Debt [Line Items] | |||||
| Credit Facility | 500,000,000 | $ 700,000,000 | $ 500,000,000 | ||
| Required debt to total capitalization ratio | 65.00% | ||||
| Basis points | 50.0 | ||||
| Amount outstanding at period end | 500,000,000 | ||||
| Available | $ 0 | ||||