Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Customer allowance for uncollectible accounts	$ 248	$ 283
Other allowance for uncollectible accounts	49	36
Accumulated depreciation and amortization	$ 23,590	$ 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	$ 75	$ 103
Other allowance for uncollectible accounts	1	1
Accumulated depreciation and amortization	11,972	12,206
Commonwealth Edison Co [Member]
Customer allowance for uncollectible accounts	65	61
Other allowance for uncollectible accounts	21	20
Accumulated depreciation and amortization	5,046	4,684
PECO Energy Co [Member]
Customer allowance for uncollectible accounts	54	53
Other allowance for uncollectible accounts	7	8
Accumulated depreciation and amortization	3,670	3,561
Baltimore Gas and Electric Company [Member]
Customer allowance for uncollectible accounts	13	16
Other allowance for uncollectible accounts	4	4
Accumulated depreciation and amortization	3,772	3,633
Pepco Holdings LLC [Member]
Customer allowance for uncollectible accounts	41	50
Other allowance for uncollectible accounts	16	3
Accumulated depreciation and amortization	1,124	841
Potomac Electric Power Company [Member]
Customer allowance for uncollectible accounts	16	20
Other allowance for uncollectible accounts	8	1
Accumulated depreciation and amortization	3,473	3,354
Delmarva Power and Light Company [Member]
Customer allowance for uncollectible accounts	10	12
Other allowance for uncollectible accounts	1	1
Accumulated depreciation and amortization	1,407	1,329
Atlantic City Electric Company [Member]
Customer allowance for uncollectible accounts	15	18
Other allowance for uncollectible accounts	5	1
Accumulated depreciation and amortization	$ 1,192	$ 1,137