Early Nuclear Plant Retirements Early Nuclear Plant Retirements Table (Details) - USD ($) $ in Millions				12 Months Ended
		Dec. 17, 2016	Jun. 16, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Nuclear Fuel Amortization	[1]			$ 1,096	$ 1,159	$ 1,116
Other, net				1,056	413	$ (46)
Inventory, Raw Materials and Supplies, Gross				1,311	1,274
Property, plant and equipment, net				74,202	71,555
Facility Closing [Member] | Clinton and Quad Cities [Member]
Property, Plant and Equipment [Line Items]
Restructuring Reserve, Accelerated Depreciation					712
Nuclear Fuel Amortization					60
Other Cost and Expense, Operating		$ (120)	$ 146		26
Accretion Expense, Including Asset Retirement Obligations					2
Other, net					(86)
Other Expenses					$ 714
Facility Closing [Member] | Three Mile Island [Member]
Property, Plant and Equipment [Line Items]
Restructuring Reserve, Accelerated Depreciation				250
Nuclear Fuel Amortization				12
Other Cost and Expense, Operating				77
Accretion Expense, Including Asset Retirement Obligations				0
Other, net				0
Other Expenses				339
Facility Closing [Member] | Salem [Member]
Property, Plant and Equipment [Line Items]
Inventory, Raw Materials and Supplies, Gross				44
Nuclear Fuel, Net of Amortization				113
Property, plant and equipment, net				439
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress				33
Asset Retirement Obligation				$ (442)

[1] Included in Purchased power and fuel expense on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.