OTHER CONTINGENCIES AND COMMITMENTS (Interim Rate Relief Subject to Refund) (Details) $ in Millions	Sep. 21, 2021 USD ($)	Sep. 30, 2021 USD ($) catastrophicEvent	Oct. 23, 2020 USD ($)	Sep. 30, 2020 USD ($)	Aug. 07, 2019 USD ($)	Apr. 25, 2019 USD ($)	Mar. 30, 2018 USD ($) catastrophicEvent
Loss Contingencies [Line Items]
Expenses and capital expenditures, disallowed costs		$ 1,625
CEMA Interim Rate Relief
Loss Contingencies [Line Items]
Cost recovery						$ 373
Revised cost recovery, increase to revenue requirement					$ 669
CEMA Interim Rate Relief | Mid 2016 - Early 2017
Loss Contingencies [Line Items]
Cost recovery							$ 183
Number of catastrophic events | catastrophicEvent							7
CEMA Interim Rate Relief | 2016 to 2017
Loss Contingencies [Line Items]
Cost recovery							$ 405
WMCE Interim Rate Relief
Loss Contingencies [Line Items]
Number of catastrophic events | catastrophicEvent		10
Expenses and capital expenditures, disallowed costs				$ 1,180
Expenses and capital expenditures, capital expenditures				801
Cost recovery, increase to revenue requirement				$ 1,280
Capital expenditures for future recovery			$ 447
Interim revenue requirement	$ 447
Loss Contingency, Amortization Period	17 months
Additional revenue requirement	$ 591
Additional amortization period	24 months
WMCE Interim Rate Relief | Fire hazard prevention memorandum account
Loss Contingencies [Line Items]
Cost recovery		$ 293
WMCE Interim Rate Relief | Fire risk and wildfire mitigation memorandum account
Loss Contingencies [Line Items]
Cost recovery		740
WMCE Interim Rate Relief | Catastrophic event memorandum account
Loss Contingencies [Line Items]
Cost recovery		$ 251