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Rate and Regulatory Matters (Schedule of Regulatory Assets) (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2021
Dec. 31, 2020
Regulatory Assets [Line Items]    
Regulatory Assets $ 100,738 $ 118,144
Retirement Benefits [Member]    
Regulatory Assets [Line Items]    
Regulatory Assets $ 24,926 $ 45,419
Remaining recovery period Various Various
Income Taxes [Member]    
Regulatory Assets [Line Items]    
Regulatory Assets $ 70,427 $ 66,759
Remaining recovery period Various Various
Rate Cases, Tank Painting, and Other [Member]    
Regulatory Assets [Line Items]    
Regulatory Assets $ 5,385 $ 5,966
Remaining recovery period 2-10 years 2-10 years