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Derivative and Hedging Instruments (Details-5)
3 Months Ended 9 Months Ended
Sep. 30, 2019
USD ($)
counterparty
Sep. 30, 2018
USD ($)
Sep. 30, 2019
USD ($)
counterparty
Sep. 30, 2018
USD ($)
Dec. 31, 2018
USD ($)
Counterparties in net liability position or default [Abstract]          
Derivative, net liability position of counterparties $ 0   $ 0   $ 0
Number of counterparties in default | counterparty 0   0    
Commodity Derivative Contracts [Member] | Fuel For Electric Generation Purchased Power [Member]          
Realized losses (gains) on income statement [Line Items]          
Realized losses (gains) on income statement $ 471,000 $ (145,000) $ 1,038,000 $ 39,000  
Commodity Derivative Contracts [Member] | Cost Of Gas Sold Expense [Member]          
Realized losses (gains) on income statement [Line Items]          
Realized losses (gains) on income statement 83,000 0 460,000 637,000  
Financial Transmission Rights [Member] | Fuel For Electric Generation Purchased Power [Member]          
Realized losses (gains) on income statement [Line Items]          
Realized losses (gains) on income statement (429,000) (150,000) (503,000) (625,000)  
Financial Transmission Rights [Member] | Cost Of Gas Sold Expense [Member]          
Realized losses (gains) on income statement [Line Items]          
Realized losses (gains) on income statement 0 0 0 0  
Purchased Power Agreement [Member]          
Derivative collateral required to be posted for PPA [Abstract]          
Minimum collateral that may be required to be posted 20,000,000.0   20,000,000.0    
Maximum collateral that may be required to be posted 40,000,000.0   40,000,000.0    
Collateral posted 0   0    
Purchased Power Agreement [Member] | Fuel For Electric Generation Purchased Power [Member]          
Realized losses (gains) on income statement [Line Items]          
Realized losses (gains) on income statement (505,000) 328,000 (1,257,000) 1,283,000  
Purchased Power Agreement [Member] | Cost Of Gas Sold Expense [Member]          
Realized losses (gains) on income statement [Line Items]          
Realized losses (gains) on income statement $ 0 $ 0 $ 0 $ 0