Variable Interest Entities - Narrative (Details) (USD $)	9 Months Ended			9 Months Ended			0 Months Ended			9 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2014 VIE	Aug. 18, 2014	Dec. 31, 2013 VIE	Sep. 30, 2014 Exelon Generation Co L L C [Member]	Mar. 31, 2014 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Apr. 01, 2014 Exelon Generation Co L L C [Member] Variable Interest Entity, Primary Beneficiary [Member]	Apr. 01, 2014 Exelon Generation Co L L C [Member] Variable Interest Entity, Primary Beneficiary [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member] Variable Interest Entity, Primary Beneficiary [Member] Equity Method Investment Variable Interest Entities [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Sep. 30, 2013 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Sep. 30, 2014 Constellation Energy Nuclear Group [Member]	Apr. 01, 2014 Constellation Energy Nuclear Group [Member]	Apr. 01, 2014 Constellation Energy Nuclear Group [Member] Exelon Generation Co L L C [Member]	Apr. 01, 2014 Financial Guarantee [Member] Constellation Energy Nuclear Group [Member]	Apr. 01, 2014 Payment Guarantee [Member] Constellation Energy Nuclear Group [Member]	Apr. 01, 2014 Payment Guarantee [Member] Constellation Energy Nuclear Group [Member] Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Number of Variable Interest Entities not consolidated by equity holders	8		8
Number Of Variable Interest Entities Consolidated	6		4
Equity Method Investment, Ownership Percentage		67.00%			50.01%
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain							$ 261,000,000
Remittance of payments received from customers for rate stabilization to BondCo.											21,000,000	24,000,000	63,000,000	63,000,000
Related Party Transaction Required Purchase Of Power Percentage				85.00%
Due from Affiliates																	400,000,000
Severance Benefits Obligations Balance																6,000,000
Guarantor Obligations, Current Carrying Value	75,000,000			4,000,000				7,000,000	637,000,000
Related Party Purchase Of Nuclear Output By Third Party Percentage				49.99%
Payables to affiliates				124,000,000		181,000,000													245,000,000	205,000,000
Guarantor Obligations, Maximum Exposure, Undiscounted	9,542,000,000			6,136,000,000						260,000,000								165,000,000
Payments for Restructuring	$ 36,000,000			$ 5,000,000						$ 4,000,000					$ 4,000,000