Early Nuclear Plant Retirements Early Nuclear Plant Retirement - Pretax Expense (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended		12 Months Ended
		Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Property, plant and equipment, net		$ 75,284	$ 74,202			$ 75,284		$ 74,202
Other, net		44			$ 177	17	$ 434
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] | Salem [Member]
Inventory, Raw Materials, Gross		45				45
Nuclear Fuel, Net of Amortization		94				94
Property, plant and equipment, net		611				611
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress		28				28
Asset Retirement Obligation		(451)				(451)
Facility Closing [Member] | TMI,OysterCreek [Member]
Restructuring and Related Cost, Accelerated Depreciation	[4],[5]	152				289
Nuclear Fuel Amortization	[4]	19				34
Other Cost and Expense, Operating	[6]	2				28
Restructuring and Related Cost, Incurred Cost		$ 173				$ 351

[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 and Oyster Creek for the three and six months ended June 30, 2018. The Oyster Creek year-to-date amounts are from February 2, 2018 through June 30, 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.