Debt and Credit Agreements - Commercial Paper Borrowings Outstanding (Details) - USD ($) $ in Millions	Apr. 01, 2016	Mar. 31, 2016	Dec. 31, 2015
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Commercial paper borrowings		$ 1,378	$ 0
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Commercial paper borrowings		643	294
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings		150	210
PEPCO Holdings Inc [Member]
Short-term Debt [Line Items]
Commercial paper borrowings		442	484
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings		0	64
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings		75	105
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Commercial paper borrowings		0	$ 5
Revolving Credit Facility [Member] | Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity		$ 150
Revolving Credit Facility [Member] | Subsequent Event [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 200