Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Customer allowance for uncollectible accounts	$ 257	$ 283
Other allowance for uncollectible accounts	40	36
Accumulated depreciation and amortization	$ 24,266	$ 22,902
Common Stock, Shares Authorized	2,000	2,000
Common Stock, Shares, Outstanding	972	968
Treasury Stock, Shares held	2	2
Exelon Generation Co L L C [Member]
Customer allowance for uncollectible accounts	$ 96	$ 103
Other allowance for uncollectible accounts	1	1
Accumulated depreciation and amortization	12,902	12,206
Commonwealth Edison Co [Member]
Customer allowance for uncollectible accounts	59	61
Other allowance for uncollectible accounts	18	20
Accumulated depreciation and amortization	4,949	4,684
PECO Energy Co [Member]
Customer allowance for uncollectible accounts	53	53
Other allowance for uncollectible accounts	6	8
Accumulated depreciation and amortization	3,636	3,561
Baltimore Gas and Electric Company [Member]
Customer allowance for uncollectible accounts	14	16
Other allowance for uncollectible accounts	4	4
Accumulated depreciation and amortization	3,720	3,633
Pepco Holdings LLC [Member]
Customer allowance for uncollectible accounts	35	50
Other allowance for uncollectible accounts	11	3
Accumulated depreciation and amortization	1,032	841
Potomac Electric Power Company [Member]
Customer allowance for uncollectible accounts	13	20
Other allowance for uncollectible accounts	6	1
Accumulated depreciation and amortization	3,431	3,354
Delmarva Power and Light Company [Member]
Customer allowance for uncollectible accounts	10	12
Other allowance for uncollectible accounts	2	1
Accumulated depreciation and amortization	1,380	1,329
Atlantic City Electric Company [Member]
Customer allowance for uncollectible accounts	11	18
Other allowance for uncollectible accounts	3	1
Accumulated depreciation and amortization	$ 1,179	$ 1,137