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Commitment, Contingencies And Guarantees: Manufactured Gas Plants (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Dec. 31, 2024
Loss Contingencies [Line Items]
Regulatory assets	$ 391.2	$ 427.7
Manufactured Gas Plant | Black Hills Energy - Iowa Gas
Loss Contingencies [Line Items]
Insurance Settlements Receivable, Noncurrent	1.5
Accrual for Environmental Loss Contingencies, Gross, Total		$ 9.7
Site remediation cost	11.5
Insurance recovery asset	1.5
Regulatory assets	$ 11.5

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