Employee Benefit Plans: Assumptions (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Minimum
Defined Benefit Plan Disclosure [Line Items]
Trend Year	2035	2034
Maximum
Defined Benefit Plan Disclosure [Line Items]
Trend Year	2033	2034
Black Hills Corporation \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Post-65 for next year - All Plans	7.50%	6.69%
Post-65 Ultimate trend rate - Black Hills Corp	4.50%	4.50%
Black Hills Corporation \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Post-65 for next year - All Plans	6.50%	5.81%
Post-65 Ultimate trend rate - Black Hills Corp	4.50%	4.50%
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost effective discount rate	5.63%	4.99%	5.17%
Rate of increase in compensation levels	3.04%	3.04%	3.06%
Interest cost effective discount rate	4.99%	5.17%	2.88%
Expected long-term rate of return on assets	6.00%	6.00%	4.25%
Rate of increase in compensation levels	3.04%	3.06%	3.08%
Defined Benefit Plan Assumptions Used In Calculating Net Periodic Benefit Cost Expected Rate of Return On Assets For Next Fiscal Year	6.50%
2025	$ 24.4
2026	24.8
2027	25.1
2028	25.1
2029	25.6
2030 - 2034	$ 123.5
Pension Plan \| Black Hills Corporation Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Post-65 for next year - All Plans	5.63%
Supplemental Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost effective discount rate	5.56%	4.93%	5.13%
Rate of increase in compensation levels	0.00%	0.00%	0.00%
Interest cost effective discount rate	4.93%	5.13%	2.77%
Rate of increase in compensation levels	0.00%	0.00%	0.00%
2025	$ 2.8
2026	2.8
2027	2.7
2028	2.7
2029	2.5
2030 - 2034	$ 11.3
Healthcare Plan
Defined Benefit Plan Disclosure [Line Items]
Interest cost effective discount rate	5.60%	4.97%	5.14%
Interest cost effective discount rate	4.97%	5.14%	2.79%
Expected long-term rate of return on assets	3.50%	3.10%	1.70%
2025	$ 5.3
2026	5.1
2027	5.0
2028	4.8
2029	4.7
2030 - 2034	$ 21.4

Defined benefit plan assumptions used calculating benefit obligation discount rate interest cost.

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- Definition

Defined benefit plan assumptions used calculating net periodic benefit cost discount rate interest cost.

+ References

No definition available.

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- Definition

An assumption for the next fiscal year as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation

+ References

No definition available.

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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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- Definition

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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- Definition

Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

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- 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.

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- Definition

Amount of benefit for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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- Definition

Amount of benefit for defined benefit plan expected to be paid in next fiscal year following current fiscal year.

+ References

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- Definition

Amount of benefit for defined benefit plan expected to be paid in fifth fiscal year following current fiscal year.

+ References

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- Definition

Amount of benefit for defined benefit plan expected to be paid in fourth fiscal year following current fiscal year.

+ References

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- Definition

Amount of benefit for defined benefit plan expected to be paid in third fiscal year following current fiscal year.

+ References

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- Definition

Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year.

+ References

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- Definition

Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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- Definition

Ultimate trend rate for health care cost for defined benefit postretirement plan.

+ References

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- Definition

Year ultimate health care cost trend rate is expected to be reached, in YYYY format.

+ References

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