Regulatory Matters Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Purchase Of Receivables [Line Items]
Purchased receivables	$ 343	$ 229
Allowance for uncollectible accounts	(38)	(31)
Purchased receivables, net	$ 305	198
Discount rate	1.00%
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	$ 96	103
Allowance for uncollectible accounts	(16)	(16)
Purchased receivables, net	80	87
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	75	67
Allowance for uncollectible accounts	(8)	(7)
Purchased receivables, net	67	60
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	66	59
Allowance for uncollectible accounts	(8)	(8)
Purchased receivables, net	58	51
PEPCO Holdings Inc [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables		100
Allowance for uncollectible accounts		(6)
Purchased receivables, net		94
PEPCO Holdings Inc [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	106
Allowance for uncollectible accounts	(6)
Purchased receivables, net	100
Potomac Electric Power Company [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables		70
Allowance for uncollectible accounts		(4)
Purchased receivables, net		66
Potomac Electric Power Company [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	77
Allowance for uncollectible accounts	(4)
Purchased receivables, net	73
Delmarva Power and Light Company [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables		11
Allowance for uncollectible accounts		0
Purchased receivables, net		11
Delmarva Power and Light Company [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	11
Allowance for uncollectible accounts	0
Purchased receivables, net	11
Atlantic City Electric Company [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables		19
Allowance for uncollectible accounts		(2)
Purchased receivables, net		$ 17
Atlantic City Electric Company [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Purchased receivables	18
Allowance for uncollectible accounts	(2)
Purchased receivables, net	$ 16