Leases - EEGH - Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Operating	$ 151	$ 170
Finance:
Amortization	18	16
Short-term	20	7
Lease, Cost	$ 821	$ 857
Operating Lease, Weighted Average Remaining Lease Term	7 years 4 months 24 days	7 years 7 months 6 days
Finance Lease, Weighted Average Remaining Lease Term	27 years 6 months	28 years 9 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	4.50%	5.20%
Finance Lease, Weighted Average Discount Rate, Percent	8.50%	8.60%
Eastern Energy Gas Holdings, LLC [Member]
Lessee, Lease, Description [Line Items]
Operating	$ 7	$ 7
Finance:
Short-term	5	7
Lease, Cost	$ 12	$ 14
Operating Lease, Weighted Average Remaining Lease Term	11 years 6 months	11 years 2 months 12 days
Finance Lease, Weighted Average Remaining Lease Term	4 years 8 months 12 days	5 years 7 months 6 days
Operating Lease, Weighted Average Discount Rate, Percent	4.40%	4.40%
Finance Lease, Weighted Average Discount Rate, Percent	2.60%	4.10%