SAN ONOFRE NUCLEAR GENERATING STATION - ASSET RETIREMENT OBLIGATION AND SPENT NUCLEAR FUEL (Details) - San Diego Gas and Electric Company [Member] $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Decommissioning liability	$ 579
Cost study estimate decommissioning escalated	860
2021	110
2022	83
2023	63
2024	45
2025	44
Thereafter	$ 697