Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Accounts receivable, allowance for uncollectible accounts	$ 56	$ 40
Series A preferred stock, par value	$ 0.01	$ 0.01
Series A preferred stock, shares authorized	18,000	18,000
Series A preferred stock, shares outstanding	18,000	12,600
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	400,000,000	400,000,000
Common stock, shares outstanding	254,289,261	252,728,684
Potomac Electric Power Co [Member]
Accounts receivable, allowance for uncollectible accounts	$ 17	$ 16
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares outstanding	100	100
Delmarva Power & Light Co/De [Member]
Accounts receivable, allowance for uncollectible accounts	$ 17	$ 11
Common stock, par value	$ 2.25	$ 2.25
Common stock, shares authorized	1,000	1,000
Common stock, shares outstanding	1,000	1,000
Atlantic City Electric Co [Member]
Accounts receivable, allowance for uncollectible accounts	$ 17	$ 9
Common stock, par value	$ 3.00	$ 3.00
Common stock, shares authorized	25,000,000	25,000,000
Common stock, shares outstanding	8,546,017	8,546,017