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The regulatory treatment under flow-through accounting was applied for this tax benefit generated by utility costs that were previously capitalized for tax purposes in a rate case settlement and resulted in a lower rate increase. 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Electric , Natural Gas and Coal Retail - Electric , Natural Gas and Coal [Member] Retail - Electric , Natural Gas and Coal Long-term Contract for Purchase of Electric Power [Domain] Long-term Contract for Purchase of Electric Power [Domain] Inter-company Revenues Intersegment Eliminations [Member] Other regulatory liabilities Other Regulatory Liabilities [Member] Other regulatory liabilities [Member] Operations and maintenance Other Cost and Expense, Operating Regulatory liabilities, current Less current regulatory liabilities Regulatory Liability, Current Black Hills Energy, Colorado Gas Black Hills Energy, Colorado Gas [Member] Black Hills Energy, Colorado Gas [Member] Regulatory Assets and Liabilities Disclosure [Abstract] Regulatory Assets and Liabilities Disclosure [Abstract] Retirement Plan Type [Domain] Retirement Plan Type [Domain] Regulatory assets Regulatory assets Regulatory Assets Employee benefit plans Pension and Other Postretirement Benefits Cost (Reversal of Cost) Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Consolidation Items [Axis] Consolidation Items [Axis] Payment for Pension and Other Postretirement Benefits [Abstract] Payment for Pension and Other Postretirement Benefits [Abstract] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Investment in privately held oil and gas company Equity Securities [Member] Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Accounts receivable, net Accounts receivable, net Accounts Receivable, after Allowance for Credit Loss, Current At The Market Equity Offering Program Shares Issued At The Market Equity Offering Program Shares Issued At The Market Equity Offering Program Shares Issued Sale of Stock [Axis] Sale of Stock [Axis] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Regulatory assets - 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Anti-dilutive shares (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount City of Colorado Springs City of Colorado Springs [Member] City of Colorado Springs Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Public Utilities, Requested Return on Equity, Percentage Public Utilities, Requested Return on Equity, Percentage Other adjustments, net Other Noncash Income (Expense) Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax Public Utilities, Requested Equity Capital Structure, Percentage Public Utilities, Requested Equity Capital Structure, Percentage Environmental Environmental [Member] Environmental costs associated with utility property [Member] Equity Component [Domain] Equity Component [Domain] Colorado Public Utilities Commission (CPUC) Colorado Public Utilities Commission (CPUC) [Member] Colorado Public Utilities Commission (CPUC) [Member] Dividends paid on common stock Payments of Dividends Total property, plant and equipment, net Property, Plant and Equipment, Net Entity Tax Identification Number Entity Tax Identification Number Contract or Notional Amounts and Terms of Marketing Activities and Derivative Commodity Instruments Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Public Utilities, Requested Debt Capital Structure, Percentage Public Utilities, Requested Debt Capital Structure, Percentage Net income available for common stock Net income available for common stock Net Income (Loss) Attributable to Parent Changes in certain operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Black Hills Energy, Nebraska Gas Black Hills Energy, Nebraska Gas [Member] Black Hills Energy, Nebraska Gas Distributions to noncontrolling interest Payments to Noncontrolling Interests Other comprehensive income, net of tax Other comprehensive income (loss), net of tax Other Comprehensive Income (Loss), Net of Tax Regulatory Asset [Axis] Regulatory Asset [Axis] Schedule Of Regulatory Assets And Liabilities [Table] Schedule Of Regulatory Assets And Liabilities [Table] A table of assets and liabilities that are created when regulatory agencies permit public utilities to defer recognitiion of certain revenues or costs included in rate setting. Taxes - property and production Taxes, Miscellaneous Market - off-system sales Market Off-System Sales [Member] Market Off-System Sales [Member] Total current assets Assets, Current Current Fiscal Year End Date Current Fiscal Year End Date Operating expenses: Operating Expenses [Abstract] Earnings per share of common stock: Earnings Per Share [Abstract] Reclassification of net realized gains/losses, (tax) benefit Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Financing Receivable, Current, Allowance for Credit Loss Financing Receivable, Current, Allowance for Credit Loss [Table Text Block] Accumulated Defined Benefit Plans Adjustment Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Derivative, Remaining Maturity Derivative, Remaining Maturity Equity: Stockholders' Equity Attributable to Parent [Abstract] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Electric wholesale contracts Energy Related Derivative [Member] Document Fiscal Period Focus Document Fiscal Period Focus Regulatory Matters Schedule of Regulatory Assets and Liabilities [Text Block] Reclassification adjustments of benefit plan liability - net gain (net of tax of $(149), $(92), $(426) and $(197), respectively) Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax Cash surrender value of life insurance contracts Cash Surrender Value [Member] Contributions by Employer Defined Benefit Plan, Plan Assets, Contributions by Employer Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] Entity Filer Category Entity Filer Category Common Stock Common Stock [Member] Product and Service [Domain] Product and Service [Domain] Reclassification Out of Accumulated Other Comprehensive Income (Loss) Reclassification out of Accumulated Other Comprehensive Income [Table Text Block] Natural gas basis swaps purchased Basis Swap [Member] Issuance of common stock, shares Stock Issued During Period, Shares, New Issues Debt Instrument, Interest Rate, Stated Percentage Debt Instrument, Interest Rate, Stated Percentage Additions Charged to Costs and Expenses Accounts Receivable, Credit Loss Expense (Reversal) Accounts Receivable, Credit Loss Expense (Reversal) Equity compensation - (in shares) Share-based Payment Arrangement [Member] Less: accumulated depreciation and depletion Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Total other income (expense) Nonoperating Income (Expense) Hedging Relationship [Domain] Hedging Relationship [Domain] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Basic (in shares) Weighted average shares - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Subsequent Events [Abstract] Subsequent Events [Abstract] Treasury Stock (in shares) Treasury Stock, Shares Cash Flow Hedging Cash Flow Hedging [Member] Sale of Stock [Domain] Sale of Stock [Domain] Carrying Amount Reported Value Measurement [Member] Revenue Revenue from Contract with Customer [Text Block] Interest (net of amounts capitalized) Interest Paid, Excluding Capitalized Interest, Operating Activities Fair Value Hedges, Net Fair Value Hedges, Net Public Utilities, Number of Gas Distribution Territories Consolidating Public Utilities, Number of Gas Distribution Territories Consolidating Public Utilities, Number of Gas Distribution Territories Consolidating Total equity Total equity Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest Investments Investment [Table Text Block] Additional paid-in capital Additional Paid in Capital Long-term Debt, Fair Value Long-term Debt, Fair Value Revenues Total revenues Revenues Income tax (expense) Income tax benefit (expense) Income Tax Expense (Benefit) Income taxes Income Taxes Paid, Net Cash, restricted cash and cash equivalents at beginning of period Cash, restricted cash and cash equivalents at end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Condensed Statement of Income Captions [Line Items] Condensed Statement of Income Captions [Line Items] Derivative Liabilities, Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Accrued liabilities Total accrued liabilities Accrued Liabilities, Current Public Utilities, Requested Rate Increase (Decrease), Amount Public Utilities, Requested Rate Increase (Decrease), Amount Earnings (loss) per share, Diluted (usd per share) Earnings Per Share, Diluted Local Phone Number Local Phone Number Schedule of Short-term Debt Schedule of Short-term Debt [Table Text Block] Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Cumulative Effect, Period of Adoption [Domain] Cumulative Effect, Period of Adoption [Domain] Public Utilities, Requested Term of Rate Recovery Public Utilities, Requested Term of Rate Recovery Public Utilities, Requested Term of Rate Recovery Reconciliation of Assets from Segment to Consolidated Reconciliation of Assets from Segment to Consolidated [Table Text Block] Derivative [Line Items] Derivative [Line Items] Cash Flow Hedging Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Consolidation, Eliminations Consolidation, Eliminations [Member] Entity Address, Address Line One Entity Address, Address Line One Investments, All Other Investments [Abstract] Investments, All Other Investments [Abstract] Energy [Domain] Energy [Domain] Entity Emerging Growth Company Entity Emerging Growth Company Deferred income taxes Deferred Income Tax Expense (Benefit) Inter-company Operating Revenue Intercompany Customers [Member] Intercompany Customers [Member] External Operating Revenue External Customers [Member] External Customers Transportation Transportation [Member] Transportation [Member] Maximum Maximum [Member] Noncontrolling Interest Noncontrolling Interest [Member] Materials and supplies Inventory, Raw Materials and Supplies, Gross Dividends on Common Stock Dividends, Common Stock, Cash Public Utilities, Approved Return on Equity, Percentage Public Utilities, Approved Return on Equity, Percentage Retained Earnings Retained Earnings [Member] Measurement Basis [Axis] Measurement Basis [Axis] Noncontrolling interest Noncontrolling Interest in Variable Interest Entity Short-term Debt, Type [Domain] Short-term Debt, Type [Domain] Effective Tax Rate Effective Income Tax Rate Reconciliation, Percent Schedule of Net Benefit Costs Schedule of Net Benefit Costs [Table Text Block] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Net cash (used in) investing activities Net Cash Provided by (Used in) Investing Activities Regulatory liabilities - current Increase (Decrease) in Regulatory Liabilities Discount Rate Used in Valuation of Fair Value of Oil and Gas Reserve Quantities Discount Rate Used in Valuation of Fair Value of Oil and Gas Reserve Quantities Discount Rate Used in Valuation of Fair Value of Oil and Gas Reserve Quantities Deferred credits and other liabilities: Liabilities, Noncurrent [Abstract] Accounts payable and other current liabilities Increase (Decrease) in Other Accounts Payable and Accrued Liabilities Other Postretirement Benefits Plan Other Postretirement Benefits Plan [Member] Trading Symbol Trading Symbol Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Regulatory Liability [Axis] Regulatory Liability [Axis] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Fair Value Hedge Assets Fair Value Hedge Assets Treasury stock, at cost – 24,897 and 3,956 shares, respectively Treasury Stock, Value Private Placement Private Placement [Member] Pension Plan Defined Benefit Pension Plans Pension Plan [Member] Earnings Per Share Earnings Per Share [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Current liabilities: Liabilities, Current [Abstract] Entity Shell Company Entity Shell Company Segment Reporting Information Segment Reporting Information [Line Items] Fair Value, Measurements, Recurring Fair Value, Recurring [Member] Segment Reporting Segment Reporting, Policy [Policy Text Block] South Dakota Electric South Dakota Electric [Member] South Dakota Electric [Member] Recently Issued and Adopted Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Regulatory Agency [Domain] Regulatory Agency [Domain]