Leases - EEGH - Maturity Table (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	$ 152
Lessee, Operating Lease, Liability, Payments, Due Year Two	125
Lessee, Operating Lease, Liability, Payments, Due Year Three	93
Lessee, Operating Lease, Liability, Payments, Due Year Four	66
Lessee, Operating Lease, Liability, Payments, Due Year Five	50
Lessee, Operating Lease, Liability, Payments, Due after Year Five	199
Lessee, Operating Lease, Liability, Payments, Due	685
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(116)
Operating Lease, Liability	569
Finance Lease, Liability, Payment, Due [Abstract]
Finance Lease, Liability, Payments, Due Next Twelve Months	81
Finance Lease, Liability, Payments, Due Year Two	74
Finance Lease, Liability, Payments, Due Year Three	63
Finance Lease, Liability, Payments, Due Year Four	63
Finance Lease, Liability, Payments, Due Year Five	62
Finance Lease, Liability, Payments, Due after Year Five	673
Finance Lease, Liability, Payment, Due	1,016
Finance Lease, Liability, Undiscounted Excess Amount	(502)
Finance Lease, Liability	514
Lease, Liability, Payments, Due Next Twelve Months	233
Lease, Liability, Payments, Due Year Two	199
Lease, Liability, Payments, Due Year Three	156
Lease, Liability, Payments, Due Year Four	129
Lease, Liability, Payments, Due Year Five	112
Lease, Liability, Payments, Due after Year Five	872
Lease, Liability, Payments, Due	1,701
Lease, Liability, Undiscounted Excess Amount	(618)
Total Lease Liabilities	1,083	$ 1,096
Eastern Energy Gas Holdings, LLC [Member]
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months	6
Lessee, Operating Lease, Liability, Payments, Due Year Two	5
Lessee, Operating Lease, Liability, Payments, Due Year Three	4
Lessee, Operating Lease, Liability, Payments, Due Year Four	2
Lessee, Operating Lease, Liability, Payments, Due Year Five	2
Lessee, Operating Lease, Liability, Payments, Due after Year Five	19
Lessee, Operating Lease, Liability, Payments, Due	38
Lessee, Operating Lease, Liability, Undiscounted Excess Amount	(9)
Operating Lease, Liability	29	35
Finance Lease, Liability, Payment, Due [Abstract]
Finance Lease, Liability, Payments, Due Next Twelve Months	2
Finance Lease, Liability, Payments, Due Year Two	2
Finance Lease, Liability, Payments, Due Year Three	1
Finance Lease, Liability, Payments, Due Year Four	1
Finance Lease, Liability, Payments, Due Year Five	1
Finance Lease, Liability, Payments, Due after Year Five	0
Finance Lease, Liability, Payment, Due	7
Finance Lease, Liability, Undiscounted Excess Amount	(1)
Finance Lease, Liability	6	6
Lease, Liability, Payments, Due Next Twelve Months	8
Lease, Liability, Payments, Due Year Two	7
Lease, Liability, Payments, Due Year Three	5
Lease, Liability, Payments, Due Year Four	3
Lease, Liability, Payments, Due Year Five	3
Lease, Liability, Payments, Due after Year Five	19
Lease, Liability, Payments, Due	45
Lease, Liability, Undiscounted Excess Amount	(10)
Total Lease Liabilities	$ 35	$ 41