Commitment, Contingencies And Guarantees: Manufactured Gas Plants (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Loss Contingencies [Line Items]
Regulatory assets	$ 394.7	$ 427.7
Accrued liabilities	322.6	302.2
Environmental
Loss Contingencies [Line Items]
Regulatory assets	13.1	10.7
Manufactured Gas Plant
Loss Contingencies [Line Items]
Insurance Settlements Receivable, Noncurrent	1.5
Manufactured Gas Plant \| Black Hills Energy - Iowa Gas
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross		$ 9.7
Site remediation cost	11.5
Insurance recovery asset	1.5
Manufactured Gas Plant \| Gas Utilities \| Black Hills Energy - Nebraska Gas
Loss Contingencies [Line Items]
Accrual for Environmental Loss Contingencies, Gross	0.6
Settled Litigation [Member] \| Black Hills Energy - Colorado Electric
Loss Contingencies [Line Items]
Accrued liabilities	20.0
Insurance recovery receivable	$ 20.0

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Undiscounted amount of the accrual for environmental loss contingencies.

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Carrying amount due after one year of the balance sheet date (or one operating cycle, if longer) of amount due in settlement of a claim for reimbursement from an insurance company when the Company has suffered a loss covered under an insurance policy.

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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.

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