REGULATORY ASSETS, LIABILITIES, AND BALANCING ACCOUNTS (Long-Term Regulatory Assets) (Details) - USD ($) $ in Millions	10 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 9,207.0	$ 9,207.0	$ 8,978.0
Utility retained generation asset costs	1,200.0	1,200.0
Pension benefits
Regulatory Assets [Line Items]
Total long-term regulatory assets	708.0	708.0	2,245.0
Environmental compliance costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,089.0	$ 1,089.0	1,112.0
Recovery Period		32 years
Utility retained generation
Regulatory Assets [Line Items]
Total long-term regulatory assets	133.0	$ 133.0	181.0
Recovery Period		6 years
Price risk management
Regulatory Assets [Line Items]
Total long-term regulatory assets	216.0	$ 216.0	204.0
Recovery Period		19 years
Unamortized loss, net of gain, on reacquired debt
Regulatory Assets [Line Items]
Total long-term regulatory assets	37.0	$ 37.0	49.0
Recovery Period		23 years
Catastrophic event memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,119.0	$ 1,119.0	842.0
Catastrophic event memorandum account | COVID-19
Regulatory Assets [Line Items]
Total long-term regulatory assets	49.0	$ 49.0	49.0
Catastrophic event memorandum account | Minimum
Regulatory Assets [Line Items]
Recovery Period		1 year
Catastrophic event memorandum account | Maximum
Regulatory Assets [Line Items]
Recovery Period		3 years
Wildfire expense memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	347.0	$ 347.0	400.0
Fire hazard prevention memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	75.0	$ 75.0	137.0
Fire hazard prevention memorandum account | Minimum
Regulatory Assets [Line Items]
Recovery Period		1 year
Fire hazard prevention memorandum account | Maximum
Regulatory Assets [Line Items]
Recovery Period		3 years
Fire risk mitigation memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	44.0	$ 44.0	66.0
Fire risk mitigation memorandum account | Minimum
Regulatory Assets [Line Items]
Recovery Period		1 year
Fire risk mitigation memorandum account | Maximum
Regulatory Assets [Line Items]
Recovery Period		3 years
Wildfire mitigation plan memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	424.0	$ 424.0	390.0
Wildfire mitigation plan memorandum account | Minimum
Regulatory Assets [Line Items]
Recovery Period		1 year
Wildfire mitigation plan memorandum account | Maximum
Regulatory Assets [Line Items]
Recovery Period		3 years
Deferred income tax
Regulatory Assets [Line Items]
Total long-term regulatory assets	1,849.0	$ 1,849.0	908.0
Recovery Period		51 years
Insurance premium costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	207.0	$ 207.0	294.0
Insurance premium costs | Minimum
Regulatory Assets [Line Items]
Recovery Period		3 years
Insurance premium costs | Maximum
Regulatory Assets [Line Items]
Recovery Period		4 years
Wildfire mitigation balancing account
Regulatory Assets [Line Items]
Total long-term regulatory assets	273.0	$ 273.0	156.0
Wildfire mitigation balancing account | Minimum
Regulatory Assets [Line Items]
Recovery Period		1 year
Cost percentage threshold requiring approval		115.00%
Wildfire mitigation balancing account | Maximum
Regulatory Assets [Line Items]
Recovery Period		3 years
General rate case memorandum accounts
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 0.0	$ 0.0	376.0
Recovery period	22 months
General rate case memorandum accounts | Minimum
Regulatory Assets [Line Items]
Recovery Period		1 year
General rate case memorandum accounts | Maximum
Regulatory Assets [Line Items]
Recovery Period		2 years
Vegetation management balancing account
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 1,411.0	$ 1,411.0	592.0
Vegetation management balancing account | Minimum
Regulatory Assets [Line Items]
Recovery Period		1 year
Cost percentage threshold requiring approval		120.00%
Vegetation management balancing account | Maximum
Regulatory Assets [Line Items]
Recovery Period		3 years
COVID-19 Pandemic protection memorandum account
Regulatory Assets [Line Items]
Total long-term regulatory assets	49.0	$ 49.0	84.0
COVID-19 pandemic protection memorandum account, undercollection bad debt
Regulatory Assets [Line Items]
Total long-term regulatory assets	30.0	30.0
COVID-19 pandemic protection memorandum account, program and accounts receivable financing costs
Regulatory Assets [Line Items]
Total long-term regulatory assets	19.0	19.0
Other
Regulatory Assets [Line Items]
Total long-term regulatory assets	$ 1,226.0	$ 1,226.0	$ 942.0