Goodwill and Intangibles - Finite-lived Intangible Asset (Details) $ in Millions	12 Months Ended
Dec. 31, 2024 USD ($)
Amortization to be recorded as a decrease to operating revenues
Amortization to be recorded in the next five years
2025	$ 53.9
2026	55.1
2027	55.1
2028	55.1
2029	55.1
Maple Flats \| Amortization to be recorded as a decrease to operating revenues
Amortization to be recorded in the next five years
2025	0.9
2026	0.9
2027	0.9
2028	0.9
2029	0.9
PPAs \| Maple Flats
Finite-Lived Intangible Asset
Gross carrying amount	$ 13.0
Weighted average useful life	15 years

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of amortization for assets, excluding financial assets and goodwill, lacking physical substance with finite life expected to be recognized in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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