Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2016		Dec. 31, 2015
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	$ 16,776	[1]	$ 16,375	[2]
Accounts receivable, net
Allowance for uncollectible accounts	351		284
Exelon Generation Co L L C [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	8,950	[1]	8,639	[2]
Accounts receivable, net
Allowance for uncollectible accounts	73		77
Accumulated amortization of nuclear fuel	3,008		2,861
Commonwealth Edison Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,716		3,710
Accounts receivable, net
Allowance for uncollectible accounts	82		75
PECO Energy Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,139		3,101
Accounts receivable, net
Allowance for uncollectible accounts	90		83
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	3,069		3,016
Accounts receivable, net
Allowance for uncollectible accounts	53		49
PEPCO Holdings Inc [Member] | Predecessor [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation			5,341
Accounts receivable, net
Allowance for uncollectible accounts			56
PEPCO Holdings Inc [Member] | Successor [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	4
Accounts receivable, net
Allowance for uncollectible accounts	53
Potomac Electric Power Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	2,960		2,929
Accounts receivable, net
Allowance for uncollectible accounts	16		17
Delmarva Power and Light Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	1,140		1,139
Accounts receivable, net
Allowance for uncollectible accounts	19		17
Atlantic City Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation	983		968
Accounts receivable, net
Allowance for uncollectible accounts	$ 18		$ 17

[1] Includes accumulated amortization of nuclear fuel in the reactor core of $3,008 million

[2] Includes accumulated amortization of nuclear fuel in the reactor core of $2,861 million