Schedule of Power Cost Adjustment Mechanism (Details) - Subsidiaries [Member] $ in Millions	9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability, Interest	$ 1.2	$ 1.6
Under-collection [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability, Amount	49.7	51.5
Under-collection [Member] | Customer's share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability, Amount	$ 20.3	$ 21.9
Range 1 [Member] | Over-collection [Member] | Companys share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	1
Range 1 [Member] | Over-collection [Member] | Customer's share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0
Range 1 [Member] | Under-collection [Member] | Companys share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	1
Range 1 [Member] | Under-collection [Member] | Customer's share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0
Range 2 [Member] | Over-collection [Member] | Companys share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.35
Range 2 [Member] | Over-collection [Member] | Customer's share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.65
Range 2 [Member] | Under-collection [Member] | Companys share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.50
Range 2 [Member] | Under-collection [Member] | Customer's share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.50
Range 3 [Member] | Over-collection [Member] | Companys share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.10
Range 3 [Member] | Over-collection [Member] | Customer's share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.90
Range 3 [Member] | Under-collection [Member] | Companys share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.10
Range 3 [Member] | Under-collection [Member] | Customer's share [Member]
Regulatory Assets and Liabiliaties [Line Items]
Annual Power Cost Variability	0.90