Subsequent Events (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended									12 Months Ended
		Jun. 30, 2017	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Revenues				$ 8,381	$ 8,769	$ 7,623	$ 8,757	$ 7,875	$ 9,002	$ 6,910	$ 7,573		$ 33,531	$ 31,360	$ 29,447
Nuclear Fuel Amortization	[1]												1,096	1,159	1,116
Exelon Generation Co L L C [Member]
Subsequent Event [Line Items]
Revenues		$ 12		$ 4,654	$ 4,751	$ 4,174	$ 4,888	$ 4,388	$ 5,035	$ 3,589	$ 4,739		18,466	17,751	19,135
Nuclear Fuel Amortization	[1]												1,096	$ 1,159	$ 1,116
Zero emission credit costs | Exelon Generation Co L L C [Member]
Subsequent Event [Line Items]
Revenues													$ 311
Subsequent Event [Member] | Facility Closing [Member] | Oyster Creek [Member] | Exelon Generation Co L L C [Member]
Subsequent Event [Line Items]
Nuclear Fuel Amortization												$ 40
Subsequent Event [Member] | Facility Closing [Member] | Oyster Creek [Member] | Exelon Generation Co L L C [Member] | Minimum [Member]
Subsequent Event [Line Items]
Other Nonrecurring Expense			$ 25
Other Restructuring Costs			5
Restructuring and Related Cost, Accelerated Depreciation												110
Subsequent Event [Member] | Facility Closing [Member] | Oyster Creek [Member] | Exelon Generation Co L L C [Member] | Maximum [Member]
Subsequent Event [Line Items]
Other Nonrecurring Expense			35
Other Restructuring Costs			10
Restructuring and Related Cost, Accelerated Depreciation												140
Accretion Expense, Including Asset Retirement Obligations												$ 5
Subsequent Event [Member] | Facility Closing [Member] | Oyster Creek [Member] | Zero emission credit costs | Exelon Generation Co L L C [Member]
Subsequent Event [Line Items]
Revenues			150
Increase (Decrease) in Regulatory Liabilities			$ 100

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