Severance and Plant Retirements (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended				37 Months Ended
	Dec. 31, 2013	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2012
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	$ 6
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	111
Severance Charges		124	[1]
Non-Merger Severance Costs	0	99
Stock Compensation Expense		7	[1]
Other Expense Charges		7	[1]		7	[1]
Total Severance Benefits		138	[1]		138	[1]
Payments	64	27
Restructuring Reserve, Period End	53	111			111
Business Acquisition, Costs Recognized Post Merger [Abstract]
BGE rate credit of $100 per residential customer		113	[2]
Customer investment fund to invest in energy efficiency and low-income energy assistance to BGE customers		113.5
Contribution for renewable energy, energy efficiency or related projects in Baltimore		2
Charitable contributions at $7 million per year for 10 years		70
State funding for offshore wind development projects		32
Miscellaneous tax benefits		(2)
Total		328.5
Plant Retirement Cost [Abstract]
Inventory write down related to plant retirements	9
Severance [Member]
Restructuring Reserve [Roll Forward]
Severance Charges	5	124
One-time Termination Benefits [Member]
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Expense	3
Other Severance Charges [Member]
Restructuring Reserve [Roll Forward]
Severance Charges	18	19		5
Other Expense Charges		7			7
Exelon Generation Co L L C [Member]
Corporate Restructuring Severance Benefit Obligation [Line Items]
Severance charges recorded	6
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	33
Severance Charges		80	[1]
Non-Merger Severance Costs	0	34
Stock Compensation Expense		4	[1]
Other Expense Charges		4	[1]		4	[1]
Total Severance Benefits		88	[1]		88	[1]
Payments	24	9
Severance Costs Intercompany Allocation	5
Restructuring Reserve, Period End	10	33			33
Business Acquisition, Costs Recognized Post Merger [Abstract]
Charitable contributions at $7 million per year for 10 years		35
Total		35.0
Plant Retirements Reserve [LineItems]
Plant Retirement Cash Payments	2	4		4
Plant Retirement Cost [Abstract]
Plant retirement costs incurred					46
Severance benefits expense related to plant retirements	1			4	14
Inventory write down related to plant retirements	9	6			18
Plant shut-down costs	1	11		2	14
Exelon Generation Co L L C [Member] | Eddystone Generating Station [Member]
Plant Retirements Reliability Must Run Revenue [Abstract]
PlantMonthlyRevenueDuringReliabilityMustRunPeriod	6
Exelon Generation Co L L C [Member] | Schuylkill Station Unit One [Member]
Plant Retirement Positions Eliminated [Abstract]
Oil/gas-fired generation unit to be retired	166	166			166
Exelon Generation Co L L C [Member] | Riverside Station Unit Six [Member]
Plant Retirement Positions Eliminated [Abstract]
Oil/gas-fired generation unit to be retired	115
Exelon Generation Co L L C [Member] | Riverside Station Unit Four[Member]
Plant Retirement Positions Eliminated [Abstract]
Oil/gas-fired generation unit to be retired	74	115			115
Exelon Generation Co L L C [Member] | Severance [Member]
Restructuring Reserve [Roll Forward]
Severance Charges	1	38
Exelon Generation Co L L C [Member] | One-time Termination Benefits [Member]
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Expense	1
Exelon Generation Co L L C [Member] | Stock Compensation Plan [Member]
Restructuring Reserve [Roll Forward]
Stock Compensation Expense		2
Exelon Generation Co L L C [Member] | Other Severance Charges [Member]
Restructuring Reserve [Roll Forward]
Severance Charges	16	14		5
Other Expense Charges		2			2
Commonwealth Edison Co [Member]
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	1
Severance Charges		14	[1],[3]
Stock Compensation Expense		1	[1],[3]
Other Expense Charges		1	[1],[3]		1	[1],[3]
Total Severance Benefits		16	[1],[3]		16	[1],[3]
Payments	1	1
Restructuring Reserve, Period End	0	1			1
Plant Retirement Cost [Abstract]
Inventory write down related to plant retirements	0	1
Commonwealth Edison Co [Member] | Severance [Member]
Restructuring Reserve [Roll Forward]
Severance Charges		2
Commonwealth Edison Co [Member] | Other Severance Charges [Member]
Restructuring Reserve [Roll Forward]
Severance Charges	2	2
PECO Energy Co [Member]
Restructuring Reserve [Roll Forward]
Severance Charges		7	[1]
Total Severance Benefits		7	[1]		7	[1]
PECO Energy Co [Member] | Other Severance Charges [Member]
Restructuring Reserve [Roll Forward]
Severance Charges		1
Baltimore Gas and Electric Company [Member]
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Period Start	11
Severance Charges		17	[1],[3]
Stock Compensation Expense		1	[1],[3]
Other Expense Charges		1	[1],[3]		1	[1],[3]
Total Severance Benefits		19	[1],[3]		19	[1],[3]
Payments	5	1
Restructuring Reserve, Period End	6	11			11
Business Acquisition, Costs Recognized Post Merger [Abstract]
BGE rate credit of $100 per residential customer		113	[2]
Charitable contributions at $7 million per year for 10 years		28
Miscellaneous tax benefits		(2)
Total		139.0
Baltimore Gas and Electric Company [Member] | Severance [Member]
Restructuring Reserve [Roll Forward]
Severance Charges		11
Baltimore Gas and Electric Company [Member] | Other Severance Charges [Member]
Restructuring Reserve [Roll Forward]
Severance Charges		3		4
Other Expense Charges		$ 1			$ 1

[1] The amounts above include $46 million at Generation, $14 million at ComEd, $7 million at PECO, and $7 million at BGE, for amounts billed by BSC through intercompany allocations for the year ended December 31, 2013.

[2] Exelon made a $66 million equity contribution to BGE in the second quarter of 2012 to fund the after-tax amount of the rate credit as directed in the MDPSC order approving the merger transaction.

[3] Exelon, ComEd and BGE established regulatory assets of $35 million, $16 million and $19 million, respectively, for severance benefits costs for the year ended December 31, 2012. The majority of these costs are expected to be recovered over a five-year period.