Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended																																				3 Months Ended
	Mar. 31, 2014 VIE		Dec. 31, 2013 VIE		Mar. 31, 2013	Mar. 31, 2014 Commercial Agreement Variable Interest Entities [Member]		Dec. 31, 2013 Commercial Agreement Variable Interest Entities [Member]		Mar. 31, 2014 Equity Method Investment Variable Interest Entities [Member]		Dec. 31, 2013 Equity Method Investment Variable Interest Entities [Member]		Mar. 31, 2014 Investments [Member]	Dec. 31, 2013 Investments [Member] Maximum [Member]	Dec. 31, 2013 Investments [Member] Maximum [Member] Commercial Agreement Variable Interest Entities [Member]	Mar. 31, 2014 Investments [Member] Maximum [Member] Equity Method Investment Variable Interest Entities [Member]	Dec. 31, 2013 Investments [Member] Maximum [Member] Equity Method Investment Variable Interest Entities [Member]	Mar. 31, 2014 Contract Intangible Asset [Member]	Dec. 31, 2013 Contract Intangible Asset [Member] Maximum [Member]	Mar. 31, 2014 Contract Intangible Asset [Member] Maximum [Member] Commercial Agreement Variable Interest Entities [Member]	Dec. 31, 2013 Contract Intangible Asset [Member] Maximum [Member] Commercial Agreement Variable Interest Entities [Member]	Mar. 31, 2014 Payment Guarantee [Member]	Dec. 31, 2013 Payment Guarantee [Member] Maximum [Member]	Mar. 31, 2014 Payment Guarantee [Member] Maximum [Member] Equity Method Investment Variable Interest Entities [Member]	Dec. 31, 2013 Payment Guarantee [Member] Maximum [Member] Equity Method Investment Variable Interest Entities [Member]	Mar. 31, 2014 Net assets pledged for Zion Station decommissioning		Dec. 31, 2013 Net assets pledged for Zion Station decommissioning Maximum [Member]		Mar. 31, 2014 Net assets pledged for Zion Station decommissioning Maximum [Member] Commercial Agreement Variable Interest Entities [Member]		Dec. 31, 2013 Net assets pledged for Zion Station decommissioning Maximum [Member] Commercial Agreement Variable Interest Entities [Member]		Mar. 31, 2014 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]	Mar. 31, 2014 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Mar. 31, 2013 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]
Consolidated Variable Interest Entities Disclosure [Abstract]
Current Assets	$ 738		$ 484																																$ 679	$ 446	$ 53	$ 28
Non Current Assets	1,893		1,905																																1,870	1,884	3				3
Total Assets	2,631		2,389																																2,549	2,330	56	31
Current Liabilities	608		566																																525	481	78	74
Non Current Liabilites	780		774																																566	562	195	195
Total Liabilities	1,388		1,340																																1,091	1,043	273	269
Deferred tax assets	0				0																														0	0
Remittance of payments received from customers for rate stabilization to BondCo.																																							21	22
Parental guarantee provided	75		75
Variable Interest Entity, Not Primary Beneficiary, Disclosures [Abstract]
Number of Variable Interest Entities not consolidated by equity holders	5		4
Number Of Variable Interest Entities Consolidated	8		8
Variable Interest Entity Nonconsolidated Carrying Amount Assets Liabilities And Other Information [Abstract]
Total assets	457	[1]	460	[1]		113	[1]	128	[1]	344	[1]	332	[1]
Total liabilities	141	[1]	140	[1]		2	[1]	17	[1]	139	[1]	123	[1]
Our ownership interest	64	[1]	86	[1]						64	[1]	86	[1]
Other ownership interests	254	[1]	234	[1]		111	[1]	111	[1]	143	[1]	123	[1]
Our maximum exposure to loss														73	74	7	73	67	9	9	9	9	3	5	3	5	44	[2]	44	[2]	44	[2]	44	[2]
Variable Interest Entity Nonconsolidated Carrying Amount Assets Liabilities And Other Information Footnotes [Abstract]
Gross pledged assets	486		614																																486	614
Pledged assets liabilities offset	$ 443		$ 564																																$ 443	$ 564

[1] These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs.

[2] These items represent amounts on Exelon’s and Generation’s Consolidated Balance Sheets related to the asset sale agreement with ZionSolutions, LLC. The net assets pledged for Zion Station decommissioning includes gross pledged assets of $429 million and $458 million as of March 31, 2014 and December 31, 2013, respectively; offset by payables to ZionSolutions LLC of $385 million and $414 million as of March 31, 2014 and December 31, 2013, respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE.