XML 106 R87.htm IDEA: XBRL DOCUMENT v3.20.4

Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jun. 17, 2020	Dec. 31, 2019	Oct. 03, 2019
Debt Instrument [Line Items]
Total long-term debt	$ 3,561,345		$ 3,170,489
Less current maturities	8,436		5,743
Less unamortized deferred financing costs	24,809		24,650
Long-term debt, net of current maturities	3,528,100		3,140,096
Revolving Credit Facility
Debt Instrument [Line Items]
Less unamortized deferred financing costs	1,000		1,700
Corporate, Non-Segment | Senior Unsecured Notes Due 2029
Debt Instrument [Line Items]
Stated interest rate (percent)				3.05%
Corporate, Non-Segment | Senior Unsecured Notes Due 2030
Debt Instrument [Line Items]
Stated interest rate (percent)		2.50%
Corporate, Non-Segment | Senior Unsecured Notes Due 2049
Debt Instrument [Line Items]
Stated interest rate (percent)				3.875%
Black Hills Corporation | Corporate, Non-Segment
Debt Instrument [Line Items]
Long-term debt	3,026,436		2,632,178
Less unamortized debt discount	(7,013)		(6,462)
Total long-term debt	$ 3,019,423		2,625,716
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2023
Debt Instrument [Line Items]
Stated interest rate (percent)	4.25%
Long-term debt	$ 525,000		525,000
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2026
Debt Instrument [Line Items]
Stated interest rate (percent)	3.95%
Long-term debt	$ 300,000		300,000
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2027
Debt Instrument [Line Items]
Stated interest rate (percent)	3.15%
Long-term debt	$ 400,000		400,000
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2029
Debt Instrument [Line Items]
Stated interest rate (percent)	3.05%
Long-term debt	$ 400,000		400,000
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2030
Debt Instrument [Line Items]
Stated interest rate (percent)	2.50%
Long-term debt	$ 400,000		0
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2033
Debt Instrument [Line Items]
Stated interest rate (percent)	4.35%
Long-term debt	$ 400,000		400,000
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2046
Debt Instrument [Line Items]
Stated interest rate (percent)	4.20%
Long-term debt	$ 300,000		300,000
Black Hills Corporation | Corporate, Non-Segment | Senior Unsecured Notes Due 2049
Debt Instrument [Line Items]
Stated interest rate (percent)	3.88%
Long-term debt	$ 300,000		300,000
Black Hills Corporation | Corporate, Non-Segment | Corporate Term Loan Due June 2021
Debt Instrument [Line Items]
Stated interest rate (percent)	2.32%
Long-term debt	$ 1,436		7,178
Black Hills Energy, South Dakota Electric | Electric Utilities
Debt Instrument [Line Items]
Long-term debt	340,000		342,855
Less unamortized debt discount	(78)		(82)
Total long-term debt	339,922		342,773
Black Hills Energy, South Dakota Electric | Electric Utilities | Series 94 A Debt, Due 2024
Debt Instrument [Line Items]
Long-term debt	$ 0		2,855
Black Hills Energy, South Dakota Electric | Electric Utilities | First Mortgage Bonds Due 2032
Debt Instrument [Line Items]
Stated interest rate (percent)	7.23%
Long-term debt	$ 75,000		75,000
Black Hills Energy, South Dakota Electric | Electric Utilities | First Mortgage Bonds Due 2039
Debt Instrument [Line Items]
Stated interest rate (percent)	6.13%
Long-term debt	$ 180,000		180,000
Black Hills Energy, South Dakota Electric | Electric Utilities | First Mortgage Bonds Due 2044
Debt Instrument [Line Items]
Stated interest rate (percent)	4.43%
Long-term debt	$ 85,000		85,000
Wyoming Electric | Electric Utilities
Debt Instrument [Line Items]
Long-term debt	202,000		202,000
Less unamortized debt discount	0		0
Total long-term debt	$ 202,000		202,000
Wyoming Electric | Electric Utilities | First Mortgage Bonds Due 2044
Debt Instrument [Line Items]
Stated interest rate (percent)	4.53%
Long-term debt	$ 75,000		75,000
Wyoming Electric | Electric Utilities | Industrial Development Revenue Bonds Due 2021
Debt Instrument [Line Items]
Variable interest rate (percent)	0.12%
Long-term debt	$ 7,000		7,000
Wyoming Electric | Electric Utilities | Industrial Development Revenue Bonds Due 2027
Debt Instrument [Line Items]
Variable interest rate (percent)	0.12%
Long-term debt	$ 10,000		10,000
Wyoming Electric | Electric Utilities | First Mortgage Bonds Due 2037
Debt Instrument [Line Items]
Stated interest rate (percent)	6.67%
Long-term debt	$ 110,000		$ 110,000

X

- Definition

Amount of long term debt before the deduction of deferred financing costs, but after the deduction of unamortized (discount) premium and includes current maturities.

+ References

No definition available.

+ Details

Name:	bkh_LongTermDebtBeforeTheDeductionOfDeferredFinancingCosts
Namespace Prefix:	bkh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

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

X

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

+ Details

Name:	us-gaap_DeferredFinanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtPercentageBearingVariableInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_ConsolidationItemsAxis=us-gaap_CorporateNonSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2029Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2030Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2049Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2027Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2033Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_SeniorUnsecuredNotesDue2046Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_CorporateTermLoanDueJune2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=bkh_ElectricUtilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_BondsDue2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_FirstMortgageBondsDue2032Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_FirstMortgageBondsDue2039Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_FirstMortgageBondsDue2044Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

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

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_IndustrialDevelopmentRevenueBondsDue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_IndustrialDevelopmentRevenueBondsDue2027Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DebtInstrumentAxis=bkh_FirstMortgageBondsDue2037Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: