Supplemental Financial Information - Balance Sheet (Details) - USD ($) $ in Millions		6 Months Ended		12 Months Ended
		Jun. 30, 2015		Dec. 31, 2014		Mar. 31, 2014
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		$ 15,553	[1]	$ 14,742	[2]
Accounts receivable, net
Allowance for uncollectible accounts		323		311
Exelon Generation Co L L C [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		8,146	[1]	7,612	[2]
Accounts receivable, net
Allowance for uncollectible accounts		67		60
Accumulated amortization of nuclear fuel		2,804		2,673
Commonwealth Edison Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		3,571		3,432
Accounts receivable, net
Allowance for uncollectible accounts		95		84
PECO Energy Co [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		3,028		2,917
Accounts receivable, net
Allowance for uncollectible accounts	[3]	101		100
Financing Receivable, Allowance for Credit Losses		18				$ 15
CurrentFinancingReceivableAllowanceForCreditLosses		9		7
Baltimore Gas and Electric Company [Member]
Property, Plant and Equipment, Net [Abstract]
Accumulated depreciation		2,928		2,868
Accounts receivable, net
Allowance for uncollectible accounts		$ 60		$ 67

[1] Includes accumulated amortization of nuclear fuel in the reactor core of $2,804 million.

[2] Includes accumulated amortization of nuclear fuel in the reactor core of $2,673 million.

[3] Includes an allowance for uncollectible accounts of $9 million and $7 million at June 30, 2015 and December 31, 2014, respectively, related to PECO's current installment plan receivables described below.