Summary Of Significant Accounting Policies (Schedule Of Estimated Useful Lives And Balances Of Utility's Property, Plant And Equipment) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Public Utility, Property, Plant and Equipment [Line Items]
Accumulated depreciation		$ (23,456)	$ (22,012)
Net property, plant, and equipment		53,789	50,581
Utility [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant, and equipment		77,245	72,593
Electricity generating facilities [Member] | Utility [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	[1]	$ 11,843	11,308
Electricity generating facilities [Member] | Utility [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		5 years
Electricity generating facilities [Member] | Utility [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		120 years
Electricity distribution facilities [Member] | Utility [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant, and equipment		$ 31,110	29,836
Electricity distribution facilities [Member] | Utility [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		15 years
Electricity distribution facilities [Member] | Utility [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		65 years
Electricity transmission [Member] | Utility [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant, and equipment		$ 12,180	11,412
Electricity transmission [Member] | Utility [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		15 years
Electricity transmission [Member] | Utility [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		75 years
Natural gas distribution facilities [Member] | Utility [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant, and equipment		$ 12,312	11,362
Natural gas distribution facilities [Member] | Utility [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		5 years
Natural gas distribution facilities [Member] | Utility [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		60 years
Natural gas transportation and storage [Member] | Utility [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant, and equipment		$ 7,329	6,491
Natural gas transportation and storage [Member] | Utility [Member] | Minimum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		5 years
Natural gas transportation and storage [Member] | Utility [Member] | Maximum [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Useful Life		62 years
Construction Work In Progress [Member] | Utility [Member]
Public Utility, Property, Plant and Equipment [Line Items]
Total property, plant, and equipment		$ 2,471	$ 2,184

[1] Balance includes nuclear fuel inventories. Stored nuclear fuel inventory is stated at weighted-average cost. Nuclear fuel in the reactor is expensed as it is used based on the amount of energy output. (See Note 13 below.)