Property, Plant and Equipment, Net - MEC (Details) - MEC - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Public Utility, Property, Plant and Equipment [Line Items]
Plant, net	$ 19,201	$ 18,773
Property, plant and equipment, net	$ 20,301	$ 19,279
Electric
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rate	3.30%	3.20%	3.10%
Natural gas
Public Utility, Property, Plant and Equipment [Line Items]
Depreciation and amortization rate	2.80%	2.80%	2.80%
Regulated assets
Public Utility, Property, Plant and Equipment [Line Items]
Utility plant in-service	$ 26,571	$ 25,669
Accumulated depreciation and amortization	(7,376)	(6,902)
Plant, net	19,195	18,767
Construction work- in-progress	1,100	506
Regulated assets | Electric
Public Utility, Property, Plant and Equipment [Line Items]
Generation	17,397	16,980
Transmission	2,474	2,365
Distribution	4,661	4,369
Regulated assets | Natural gas
Public Utility, Property, Plant and Equipment [Line Items]
Distribution	2,039	1,955
Nonregulated assets
Public Utility, Property, Plant and Equipment [Line Items]
Nonregulated property gross	7	7
Accumulated depreciation and amortization	(1)	(1)
Plant, net	$ 6	$ 6
Minimum | Regulated assets | Electric
Public Utility, Property, Plant and Equipment [Line Items]
Useful life, generation	20 years
Useful life, transmission	52 years
Useful life, distribution	20 years
Minimum | Regulated assets | Natural gas
Public Utility, Property, Plant and Equipment [Line Items]
Useful life, distribution	29 years
Minimum | Nonregulated assets
Public Utility, Property, Plant and Equipment [Line Items]
Useful life, other	20 years
Maximum | Regulated assets | Electric
Public Utility, Property, Plant and Equipment [Line Items]
Useful life, generation	70 years
Useful life, transmission	75 years
Useful life, distribution	75 years
Maximum | Regulated assets | Natural gas
Public Utility, Property, Plant and Equipment [Line Items]
Useful life, distribution	75 years
Maximum | Nonregulated assets
Public Utility, Property, Plant and Equipment [Line Items]
Useful life, other	50 years