Supplemental Financial Information - Balance Sheet (Details) (USD $)	3 Months Ended					6 Months Ended			12 Months Ended
	Jun. 30, 2014		Mar. 31, 2014	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2014		Jun. 30, 2013	Dec. 31, 2010	Dec. 31, 2013		Sep. 30, 2000
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments	$ 0					$ 0				$ 1,925,000,000
Supplemental Financial Information Textuals [Abstract]
Payment to IRS									302,000,000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Estimated residual value of leased assets	685,000,000					685,000,000				1,465,000,000		1,600,000,000
Less: unearned income	(332,000,000)					(332,000,000)				(767,000,000)
Net investment in long-term leases	353,000,000					353,000,000				698,000,000
ImpairedAssetsFairValue	65,000,000					65,000,000
Tangible Asset Impairment Charges						86,000,000
CapitalLeaseNetInvestmentInDirectFinancingLeasesPrepaymentsReceived	1,200,000,000					1,200,000,000
Utilities Operating Expense Maintenance And Operations [Abstract]
Utilities Operating Expense, Impairments				92,000,000	21,000,000
Operating and maintenance	2,166,000,000		1,000,000	1,892,000,000		4,024,000,000		3,656,000,000
Interest Costs Incurred [Abstract]
Interest Costs Incurred								8,000,000
Cash Proceeds from Direct Finance Lease Contract Termination						335,000,000
Capital Leases Written Off	336,000,000					336,000,000
Accrued Liabilities Current [Abstract]
Taxes accrued	285,000,000					285,000,000
Total accrued expenses	1,382,000,000					1,382,000,000				1,633,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation	14,369,000,000	[1]				14,369,000,000	[1]			13,713,000,000	[2]
Accumulated amortization of nuclear fuel	2,411,000,000					2,411,000,000				2,371,000,000
Accounts receivable, net
Allowance for uncollectible accounts	293,000,000					293,000,000				272,000,000
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated other comprehensive income (loss), net	(1,906,000,000)	[3]				(1,906,000,000)	[3]			(2,040,000,000)	[3]
CPS Board San Antonio, Texas | EquipmentLeasedToOtherPartyMember
Interest Costs Incurred [Abstract]
Cash Proceeds from Direct Finance Lease Contract Termination						335,000,000		0
Exelon Generation Co L L C [Member]
Investments In Affiliates Subsidiaries Associates And Joint Ventures [Abstract]
Equity Method Investments	0					0				1,925,000,000
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
ImpairedAssetsFairValue	65,000,000					65,000,000
Tangible Asset Impairment Charges						86,000,000
Utilities Operating Expense Maintenance And Operations [Abstract]
Utilities Operating Expense, Impairments				92,000,000	21,000,000
Operating and maintenance	1,255,000,000			1,041,000,000		2,194,000,000		2,007,000,000
Interest Costs Incurred [Abstract]
Interest Costs Incurred								8,000,000
Accrued Liabilities Current [Abstract]
Total accrued expenses	819,000,000					819,000,000				976,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation	7,397,000,000	[1]				7,397,000,000	[1]			7,034,000,000	[2]
Accumulated amortization of nuclear fuel	2,411,000,000					2,411,000,000				2,371,000,000
Accounts receivable, net
Allowance for uncollectible accounts	56,000,000					56,000,000				57,000,000
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated other comprehensive income (loss), net	37,000,000	[3]				37,000,000	[3]			214,000,000	[3]
Commonwealth Edison Co [Member]
Utilities Operating Expense Maintenance And Operations [Abstract]
Operating and maintenance	316,000,000			319,000,000		603,000,000		611,000,000
Accrued Liabilities Current [Abstract]
Total accrued expenses	274,000,000					274,000,000				307,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation	3,325,000,000					3,325,000,000				3,184,000,000
Accounts receivable, net
Allowance for uncollectible accounts	71,000,000					71,000,000				62,000,000
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated other comprehensive income (loss), net	0					0				0
PECO Energy Co [Member]
Utilities Operating Expense Maintenance And Operations [Abstract]
Operating and maintenance	160,000,000			155,000,000		416,000,000		319,000,000
Accrued Liabilities Current [Abstract]
Total accrued expenses	167,000,000					167,000,000				106,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation	2,969,000,000					2,969,000,000				2,935,000,000
Accounts receivable, net
Allowance for uncollectible accounts	124,000,000					124,000,000				107,000,000
Installment plan receivables	21,000,000					21,000,000				19,000,000
Installment plan receivables uncollectible accounts reserve	(20,000,000)					(20,000,000)				(18,000,000)
Accumulated Other Comprehensive Income (Loss) [Abstract]
Accumulated other comprehensive income (loss), net	1,000,000	[3]				1,000,000	[3]			1,000,000	[3]
PECO Energy Co [Member] | Low To Medium Risk [Member]
Accounts receivable, net
Installment plan receivables uncollectible accounts reserve	(1,000,000)					(1,000,000)				(1,000,000)
PECO Energy Co [Member] | Medium Risk [Member]
Accounts receivable, net
Installment plan receivables uncollectible accounts reserve	(4,000,000)					(4,000,000)				(4,000,000)
PECO Energy Co [Member] | High Risk [Member]
Accounts receivable, net
Installment plan receivables uncollectible accounts reserve	(15,000,000)					(15,000,000)				(13,000,000)
Baltimore Gas and Electric Company [Member]
Utilities Operating Expense Maintenance And Operations [Abstract]
Operating and maintenance	163,000,000			139,000,000		326,000,000		266,000,000
Accrued Liabilities Current [Abstract]
Total accrued expenses	95,000,000					95,000,000				111,000,000
Property, Plant And Equipment [Abstract]
Accumulated depreciation	2,781,000,000					2,781,000,000				2,702,000,000
Accounts receivable, net
Allowance for uncollectible accounts	$ 42,000,000					$ 42,000,000				$ 46,000,000

[1] Includes accumulated amortization of nuclear fuel in the reactor core of $2,411 million.

[2] Includes accumulated amortization of nuclear fuel in the reactor core of $2,371 million.

[3] (a) All amounts are net of tax. Amounts in parenthesis represent a decrease in accumulated other comprehensive income.