Other Material Contingencies - Manhattan Explosion and Fire (Details) $ in Millions		1 Months Ended
	Mar. 12, 2014 building people	Feb. 28, 2017 USD ($)	Oct. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) lawsuit	Dec. 31, 2019 USD ($)
Loss Contingencies [Line Items]
Accrued regulatory liability				$ 4,569	$ 4,827
Settlement of Gas Proceedings
Loss Contingencies [Line Items]
Accrued regulatory liability				$ 22	$ 10
Manhattan Explosion and Fire
Loss Contingencies [Line Items]
Number of buildings destroyed by fire | building	2
Number of people died in explosion and fire incident | people	8
Number of people injured in explosion and fire incident (more than) | people	50
Amount of costs that will not recover from customers		$ 126
Number of pending lawsuits | lawsuit				80
Manhattan Explosion and Fire | Subsequent Event
Loss Contingencies [Line Items]
Loss contingency accrual			$ 40
Insurance receivable			$ 40
Manhattan Explosion and Fire | Settlement of Gas Proceedings
Loss Contingencies [Line Items]
Accrued regulatory liability		$ 27