Power Cost Adjustment Clause Filing (Details) - Subsidiaries [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Under-collection
Regulatory Assets [Line Items]
Annual Power Cost Variability, Amount	$ 68.0	$ 76.1
Under-collection | Companys share
Regulatory Assets [Line Items]
Annual Power Cost Variability, Amount		32.1
Under-collection | Customer's share
Regulatory Assets [Line Items]
Annual Power Cost Variability, Amount	$ 36.7	44.0
Under-collection | Customer's share plus interest [Member]
Regulatory Assets [Line Items]
Annual Power Cost Variability, Amount		46.0
Maximum Power | Customer's share plus interest [Member]
Regulatory Assets [Line Items]
Annual Power Cost Variability, Amount		$ 20.0