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WUTC (Details 4) - Cascade Natural Gas [Member] - WUTC [Member] - USD ($)
Mar. 01, 2020
Nov. 01, 2019
May 31, 2019
Mar. 29, 2019
Distribution        
Public Utilities, General Disclosures [Line Items]        
Public Utilities, Requested Rate Increase (Decrease), Amount       $ 12,700,000
Public Utilities, Requested Rate Increase (Decrease), Percentage       5.50%
Pipeline Cost Recovery Mechanism [Member]        
Public Utilities, General Disclosures [Line Items]        
Public Utilities, Requested Rate Increase (Decrease), Amount     $ 1,600,000  
Public Utilities, Requested Rate Increase (Decrease), Percentage     0.70%  
Public Utilities, Approved Rate Increase (Decrease), Amount   $ 440,000    
Public utilities, approved rate increase (decrease), percentage   0.20%    
Purchased Gas Adjustment [Member]        
Public Utilities, General Disclosures [Line Items]        
Public Utilities, Approved Rate Increase (Decrease), Amount   $ 12,800,000    
Public utilities, approved rate increase (decrease), percentage   5.70%    
Regulatory Asset, Amortization Period   3 years    
Subsequent Event [Member] | Distribution        
Public Utilities, General Disclosures [Line Items]        
Public Utilities, Approved Rate Increase (Decrease), Amount $ 6,500,000      
Public utilities, approved rate increase (decrease), percentage 2.80%