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Long-Term Debt: Debt Transactions (Details) - USD ($) $ in Thousands	Jun. 17, 2020	Mar. 24, 2020	Oct. 03, 2019	Jun. 17, 2019	Dec. 31, 2020
Corporate Term Loan Due June 2021
Debt Instrument [Line Items]
Extinguishment of Debt, Amount			$ 400,000
Senior Unsecured Notes Due 2020
Debt Instrument [Line Items]
Stated interest rate (percent)			5.875%
Extinguishment of Debt, Amount			$ 200,000
Black Hills Energy, South Dakota Electric | Series 94 A Debt, Due 2024
Debt Instrument [Line Items]
Extinguishment of Debt, Amount		$ 2,900
Corporate, Non-Segment
Debt Instrument [Line Items]
Proceeds from Issuance of Debt			700,000
Corporate, Non-Segment | Senior Unsecured Notes Due 2030
Debt Instrument [Line Items]
Proceeds from Issuance of Debt	$ 400,000
Stated interest rate (percent)	2.50%
Long-term Debt, Term	10 years
Corporate, Non-Segment | Senior Unsecured Notes Due 2029
Debt Instrument [Line Items]
Proceeds from Issuance of Debt			$ 400,000
Stated interest rate (percent)			3.05%
Long-term Debt, Term			10 years
Corporate, Non-Segment | Senior Unsecured Notes Due 2049
Debt Instrument [Line Items]
Proceeds from Issuance of Debt			$ 300,000
Stated interest rate (percent)			3.875%
Long-term Debt, Term			30 years
Corporate, Non-Segment | Black Hills Corporation | Senior Unsecured Notes Due 2030
Debt Instrument [Line Items]
Stated interest rate (percent)					2.50%
Corporate, Non-Segment | Black Hills Corporation | Senior Unsecured Notes Due 2029
Debt Instrument [Line Items]
Stated interest rate (percent)					3.05%
Corporate, Non-Segment | Black Hills Corporation | Senior Unsecured Notes Due 2049
Debt Instrument [Line Items]
Stated interest rate (percent)					3.88%
Corporate, Non-Segment | Black Hills Corporation | Corporate Term Loan Due June 2021
Debt Instrument [Line Items]
Proceeds from Issuance of Debt				$ 400,000
Stated interest rate (percent)					2.32%
Corporate, Non-Segment | Black Hills Corporation | Corporate Term Loan Due July 2020
Debt Instrument [Line Items]
Extinguishment of Debt, Amount				$ 300,000

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

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
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