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Long Term Debt (Details) - USD ($)
$ in Thousands
12 Months Ended
Oct. 01, 2014
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Debt Instrument [Line Items]        
Long-term Debt   $ 342,756 $ 342,752  
Deferred Finance Costs [Abstract]        
Deferred Finance Costs, Noncurrent, Net   3,100 3,300  
Amortization of Financing Costs   $ 100 100 $ 100
First Mortgage Bonds Due 2032 [Member]        
Debt Instrument [Line Items]        
Maturity Date   Aug. 15, 2032    
Interest Rate, Stated Percentage   7.23%    
Long-term Debt, Gross   $ 75,000 75,000  
First Mortgage Bonds Due 2039 [Member]        
Debt Instrument [Line Items]        
Maturity Date   Nov. 01, 2039    
Interest Rate, Stated Percentage   6.125%    
Long-term Debt, Gross   $ 180,000 180,000  
Unamortized Discount   $ (99) (103)  
First Mortgage Bonds Due 2044 [Member]        
Debt Instrument [Line Items]        
Maturity Date   Oct. 20, 2044    
Interest Rate, Stated Percentage   4.43%    
Long-term Debt, Gross   $ 85,000 85,000  
Bonds Due 2024 [Member]        
Debt Instrument [Line Items]        
Maturity Date   Jun. 01, 2024    
Variable Interest, Percentage Rate [1]   0.75%    
Long-term Debt, Gross [1]   $ 2,855 $ 2,855  
Electric Utilities [Member] | Black Hills Power [Member] | First Mortgage Bonds Due 2044 [Member]        
Debt Instrument [Line Items]        
Interest Rate, Stated Percentage 4.43%      
Long-term Debt, Gross $ 85,000      
Electric Utilities [Member] | Black Hills Power [Member] | Polution Control Revenue Bonds Due 2024 [Member]        
Debt Instrument [Line Items]        
Interest Rate, Stated Percentage 5.35%      
Extinguishment of Debt, Amount $ 12,000      
[1] Variable interest rate at December 31, 2015.