Commitments and Contingencies: Future Purchase Agreement - Related Party (Details)	Aug. 02, 2019 MW
Black Hills Wyoming and Wyoming Electric \| Federal Energy Regulatory Commission (FERC)
Unrecorded Unconditional Purchase Obligation [Line Items]
Pending FERC Approval - Number of Megawatts Capacity to be Purchased and Delivered Through Intercompany Agreement	60

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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