Common Equity - Stock-Based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	$ 34.8	$ 15.7	$ 35.7
Related tax benefit	9.6	4.3	9.8
Stock options
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	6.5	6.5	6.0
Restricted stock
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	7.0	6.1	7.4
Performance units
Share Based Compensation Arrangement By Share Based Payment Award
Stock-based compensation expense	$ 21.3	$ 3.1	$ 22.3

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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