Regulatory Assets and Liabilities, Regulatory Liabilities (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 100	$ 69
Regulatory Liability, Noncurrent		2,337	2,037
Deferred Income Tax Adjustments and TCJA Refunds
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	[1]	5	5
Regulatory Liability, Noncurrent	[1]	1,368	1,403
Plant Removal Costs
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		0	0
Regulatory Liability, Noncurrent		615	351
Effects of regulation on employee benefit costs
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	[2]	0	0
Regulatory Liability, Noncurrent	[2]	203	183
Renewable Resources and Environmental Initiatives
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		0	0
Regulatory Liability, Noncurrent		59	45
Sales True Up and Revenue Decoupling [Member]
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		10	0
Regulatory Liability, Noncurrent		$ 41	0
Sales True Up and Revenue Decoupling [Member] | Minimum
Regulatory Liabilities [Line Items]
Regulatory Liability, Amortization Period		1 year
Sales True Up and Revenue Decoupling [Member] | Maximum
Regulatory Liabilities [Line Items]
Regulatory Liability, Amortization Period		2 years
ITC Deferrals
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		$ 0	0
Regulatory Liability, Noncurrent		40	26
Conservation programs
Regulatory Liabilities [Line Items]
Regulatory Liability, Current	[3]	39	30
Regulatory Liability, Noncurrent	[3]	0	0
Deferred Electric, Gas, and Steam Production Costs
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		17	8
Regulatory Liability, Noncurrent		0	0
Other
Regulatory Liabilities [Line Items]
Regulatory Liability, Current		29	26
Regulatory Liability, Noncurrent		$ 11	$ 29

[1] Includes the revaluation of recoverable/regulated plant ADIT and revaluation impact of non-plant ADIT due to the TCJA.

[2] Includes regulatory amortization and certain 2018 TCJA benefits approved by the CPUC to offset the prepaid pension asset.

[3] Includes costs for conservation programs, as well as incentives allowed in certain jurisdictions.