Early Nuclear Plant Retirements Early Nuclear Plant Retirement - Pretax Expense (Details) - USD ($) $ in Millions		3 Months Ended					12 Months Ended
		Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2017
Property, plant and equipment, net		$ 74,711	$ 74,202				$ 74,202
Other, net		(28)				$ 257
Facility Closing [Member] | Salem [Member]
Inventory, Raw Materials, Gross		45
Nuclear Fuel, Net of Amortization		102
Property, plant and equipment, net		618
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		27
Asset Retirement Obligation		(446)
Facility Closing [Member] | Three Mile Island [Member]
Restructuring and Related Cost, Accelerated Depreciation	[1],[2]		109	$ 106	$ 35		250
Nuclear Fuel Amortization	[2]		4	6	2		12
Other Cost and Expense, Operating	[3]		1	5	71		77
Restructuring and Related Cost, Incurred Cost			$ 114	$ 117	$ 108		$ 339
Facility Closing [Member] | TMI,OysterCreek [Member]
Restructuring and Related Cost, Accelerated Depreciation	[4],[5]	137
Nuclear Fuel Amortization	[4]	15
Other Cost and Expense, Operating	[6]	26
Restructuring and Related Cost, Incurred Cost		$ 178

[1] Reflects incremental accelerated depreciation of plant assets, including any ARC.

[2] Reflects incremental charges for TMI including incremental accelerated depreciation and amortization from May 30, 2017 through December 31, 2017.

[3] Primarily includes materials and supplies inventory reserve adjustments, employee related costs and CWIP impairments.

[4] Reflects incremental accelerated depreciation and amortization for TMI for the quarter ended March 31, 2018, and for Oyster Creek from February 2, 2018 through March 31, 2018.

[5] Reflects incremental accelerated depreciation of plant assets, including any ARC.

[6] Primarily includes materials and supplies inventory reserve adjustments, employee related costs and CWIP impairments.