Employee Benefit Plans - EEGH - Unrecognized Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost Not Yet Recognized, Before Tax	$ 549	$ 618
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss	(23)	34
Prior service cost (credit)	(14)	(9)
Defined Benefit Plan, Net Periodic Benefit Cost Not Yet Recognized, Before Tax	(31)	28	$ 35
UNITED STATES | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss	653	612
Prior service cost (credit)	(2)	(1)
Defined Benefit Plan, Net Periodic Benefit Cost Not Yet Recognized, Before Tax	652	$ 613	$ 746
UNITED STATES | Pension Plan [Member] | Eastern Energy Gas Holdings, LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss	150
Prior service cost (credit)	0
Defined Benefit Plan, Net Periodic Benefit Cost Not Yet Recognized, Before Tax	150
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax	147
UNITED STATES | Other Postretirement Benefits Plan [Member] | Eastern Energy Gas Holdings, LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss	44
Prior service cost (credit)	(49)
Defined Benefit Plan, Net Periodic Benefit Cost Not Yet Recognized, Before Tax	(5)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax	$ (5)