Commitments and Contingencies (Wildfire loss accrual) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
2017/2018 Wildfire/Mudslide Events
Loss Contingency Accrual [Roll Forward]
Beginning balance			$ 4,383
Increase in accrued estimated losses to reflect best estimate	$ 1,265	$ 1,297	1,265	$ 1,297
Amounts paid			(3,392)
Ending balance	2,256		2,256		$ 4,383
2017/2018 Wildfire/Mudslide Events | Other current liabilities
Loss Contingency Accrual [Roll Forward]
Beginning balance			2,231
Ending balance	84		84		2,231
2017/2018 Wildfire/Mudslide Events | Other long-term liabilities
Loss Contingency Accrual [Roll Forward]
Beginning balance			2,281
Fixed payments to be made under settlement agreements			2,308
Ending balance					2,281
November 2018 - Woolsey Wildfires
Loss Contingency Accrual [Roll Forward]
Litigation settlement					2,212
November 2018 - Woolsey Wildfires | Other long-term liabilities
Loss Contingency Accrual [Roll Forward]
Beginning balance			2,152
Ending balance	2,172		2,172		2,152
Other Wildfire Related Claims
Loss Contingency Accrual [Roll Forward]
Litigation settlement					19
Other Wildfire Related Claims | Other long-term liabilities
Loss Contingency Accrual [Roll Forward]
Beginning balance			129
Ending balance	$ 136		$ 136		$ 129