Summary of Significant Accounting Policies Allowance for Funds Used During Construction (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for funds used during construction
AFUDC - Debt	$ 13.0	$ 6.9	$ 2.9
AFUDC - Equity	$ 41.0	$ 18.8	$ 7.9
Retail operations
Allowance for funds used during construction
Percentage of retail jurisdictional construction work in progress expenditure subject to AFUDC	50.00%
Average AFUDC rate (as a percent)	8.45%	8.68%	8.68%
Wholesale operations
Allowance for funds used during construction
Average AFUDC rate (as a percent)	6.70%	5.35%	1.79%

The component of the allowance for funds used during construction during the period based on an assumed rate of return on equity funds used in financing the construction of regulated assets.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 25
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481668/980-835-25-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 980
-SubTopic 835
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482064/980-835-45-1

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- Definition

Amount capitalized of allowance for funds used during construction.

+ References

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- Definition

Effective rate, including composite rate, of cost of financing additions to qualifying regulated assets, commonly called allowance for funds used during construction.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Represents the percentage of retail jurisdictional construction work in progress expenditures subject to the AFUDC calculation.

+ References

No definition available.

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