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REGULATORY MATTERS: Idaho Jurisdiction Power Cost Adjustment Mechanism (Details) - USD ($)
Jun. 01, 2019
Jun. 01, 2018
Jun. 01, 2017
Dec. 31, 2019
Dec. 31, 2018
Idaho Power Cost Adjustment Mechanism [Line Items]          
Regulatory Liabilities       $ 782,185,000 $ 764,877,000
Idaho Power Cost Adjustment          
Idaho Power Cost Adjustment Mechanism [Line Items]          
Percentage to be Shared with Customers       95.00%  
Percentage to be Shared with Entity       5.00%  
Approved Rate Increase (Decrease), Amount $ (50,100,000) $ (30,400,000) $ 10,600,000    
Regulatory Liabilities   $ 7,800,000 $ 13,000,000    
May 2018 Tax Reform Settlement Stipulation | Idaho Power Cost Adjustment          
Idaho Power Cost Adjustment Mechanism [Line Items]          
Regulatory Liabilities 2,700,000        
October 2014 Idaho Settlement Stipulation | Idaho Power Cost Adjustment          
Idaho Power Cost Adjustment Mechanism [Line Items]          
Regulatory Liabilities $ 5,025,000