FERC Approved - Number of Megawatts Capacity to be Purchased and Delivered Through Intercompany Agreement

No definition available.

Name:	bkh_FERCApprovedNumberOfMegawattsCapacityToBePurchasedAndDeliveredThroughIntercompanyAgreement
Namespace Prefix:	bkh_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

Public Utilities, Number of Gas Distribution Territories Consolidating

+ References

No definition available.

+ Details

Name:	bkh_PublicUtilitiesNumberofGasDistributionTerritoriesConsolidating
Namespace Prefix:	bkh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of public utility's approved rate increase (decrease) by regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedRateIncreaseDecreaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesGeneralDisclosuresLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of public utility's requested debt to capital, including debt and equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedDebtCapitalStructurePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of public utility's requested equity to capital, including debt and equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedEquityCapitalStructurePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of public utility's requested rate increase (decrease) with regulatory agency.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedRateIncreaseDecreaseAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of public utility's requested return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesRequestedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of the unrecognized unconditional purchase obligation, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77896938&loc=d3e25336-109308

+ Details

Name:	us-gaap_UnrecordedUnconditionalPurchaseObligationTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RegulatoryAgencyAxis=bkh_FederalEnergyRegulatoryCommissionFERCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=bkh_BlackHillsWyomingandWyomingElectricMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=bkh_RateReviewFiledwiththeRegulatoryAgencyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=bkh_NebraskaPublcServiceCommissionNPSCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=bkh_BlackHillsEnergyNebraskaGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=bkh_ColoradoPublicUtilitiesCommissionCPUCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=bkh_BlackHillsEnergyColoradoGasMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Regulatory Matters: Rate Review (Details) $ in Thousands	Jun. 01, 2020 USD ($) utility MW	May 19, 2020 USD ($)	Feb. 01, 2019 USD ($) utility
Federal Energy Regulatory Commission (FERC) \| Black Hills Wyoming and Wyoming Electric
Public Utilities, General Disclosures [Line Items]
Pending FERC Approval - Number of Megawatts Capacity to be Purchased and Delivered Through Intercompany Agreement \| MW	60
Unrecorded Unconditional Purchase Obligation, Term	11 years
Rate Review Filed with the Regulatory Agency \| Nebraska Publc Service Commission (NPSC) \| Black Hills Energy, Nebraska Gas
Public Utilities, General Disclosures [Line Items]
Public Utilities, Number of Gas Distribution Territories Consolidating \| utility	2
Public Utilities, Requested Rate Increase (Decrease), Amount	$ (17,000)
Public Utilities, Requested Equity Capital Structure, Percentage	50.00%
Public Utilities, Requested Debt Capital Structure, Percentage	50.00%
Public Utilities, Requested Return on Equity, Percentage	10.00%
Rate Review Filed with the Regulatory Agency \| Colorado Public Utilities Commission (CPUC) \| Black Hills Energy, Colorado Gas
Public Utilities, General Disclosures [Line Items]
Public Utilities, Number of Gas Distribution Territories Consolidating \| utility			2
Public Utilities, Requested Rate Increase (Decrease), Amount			$ (2,500)
Public Utilities, Approved Rate Increase (Decrease), Amount		$ 600
Public Utilities, Approved Return on Equity, Percentage		9.20%