Schedule of Power Cost Adjustment Mechanism (Details) - Subsidiaries [Member] $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Regulatory Assets [Line Items]
Annual Power Cost Variability, Interest	$ 1.0	$ 0.2
Customer's share | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability, Amount	$ 36.0	0.0
Customer's share | Range 1 | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0
Customer's share | Range 1 | Over-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0
Customer's share | Range 2 | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.50
Customer's share | Range 2 | Over-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.65
Customer's share | Range 3 | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.90
Customer's share | Range 3 | Over-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.90
Companys share | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability, Amount	$ 67.2	$ 3.5
Companys share | Range 1 | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	1
Companys share | Range 1 | Over-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	1
Companys share | Range 2 | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.50
Companys share | Range 2 | Over-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.35
Companys share | Range 3 | Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.10
Companys share | Range 3 | Over-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability	0.10