OTHER CONTINGENCIES AND COMMITMENTS (Nuclear Insurance and Diablo Canyon Outages) (Details)	6 Months Ended	12 Months Ended
	Jun. 30, 2021 USD ($) nuclear_generating_unit	Jun. 30, 2021 USD ($) outage
Long-term Purchase Commitment [Line Items]
Number of nuclear generating units (nuclear generating unit) | nuclear_generating_unit	2
Nuclear Electric Insurance Limited and European Mutual Association for Nuclear Insurance
Long-term Purchase Commitment [Line Items]
Insurance coverage, loss	$ 400,000,000	$ 400,000,000
Nuclear Electric Insurance Limited
Long-term Purchase Commitment [Line Items]
Amount of property damage and business interruption coverage provided by NEIL for Diablo Canyon	42,000,000	42,000,000
European Mutual Association for Nuclear Insurance
Long-term Purchase Commitment [Line Items]
Additional insurance coverage, loss	200,000,000	200,000,000
Amount of property damage coverage provided by NEIL	4,000,000	$ 4,000,000
Diablo Canyon Outage
Long-term Purchase Commitment [Line Items]
Number of outages experienced (outage) | outage		5
Property damage and business interruption coverage | Humboldt Bay Unit 3 | Nuclear Electric Insurance Limited
Long-term Purchase Commitment [Line Items]
Liability insurance coverage	50,000,000	$ 50,000,000
Property damage and business interruption coverage, nuclear incident | Diablo Canyon | Nuclear Electric Insurance Limited
Long-term Purchase Commitment [Line Items]
Liability insurance coverage	3,200,000,000	3,200,000,000
Property damage and business interruption coverage, non-nuclear incident | Diablo Canyon | Nuclear Electric Insurance Limited
Long-term Purchase Commitment [Line Items]
Liability insurance coverage	$ 2,500,000,000	$ 2,500,000,000