Variable Interest Entities - Carrying Amounts and Classification of Consolidated VIE Assets and Liabilities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014		Dec. 31, 2013		Sep. 30, 2013	Sep. 30, 2014 Variable Interest Entity, Primary Beneficiary [Member]	Apr. 01, 2014 Variable Interest Entity, Primary Beneficiary [Member]	Dec. 31, 2013 Variable Interest Entity, Primary Beneficiary [Member]	Sep. 30, 2014 Exelon Generation Co L L C [Member]		Dec. 31, 2013 Exelon Generation Co L L C [Member]		Sep. 30, 2014 Exelon Generation Co L L C [Member] Variable Interest Entity, Primary Beneficiary [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member] Variable Interest Entity, Primary Beneficiary [Member]	Sep. 30, 2014 Baltimore Gas and Electric Company [Member]		Dec. 31, 2013 Baltimore Gas and Electric Company [Member]		Sep. 30, 2014 Baltimore Gas and Electric Company [Member] Variable Interest Entity, Primary Beneficiary [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Current Assets	$ 1,071	[1],[2]	$ 484	[1]					$ 1,018	[2]	$ 446				$ 47		$ 28
Non Current Assets	7,384	[1],[2]	1,905	[1]					7,367	[2]	1,884				3		3
Total Assets	8,455	[1],[2]	2,389	[1]					8,385	[2]	2,330				50		31
Current Liabilities	545	[1],[2]	566	[1]					460	[2]	481				79		74
Non Current Liabilities	2,671	[1],[2]	774	[1]					2,499	[2]	562				158		195
Total Liabilities	3,216	[1],[2]	1,340	[1]					2,959	[2]	1,043				237		269
Assets	85,264		79,924		79,924	7,773	6,000	1,755	45,019		41,232		7,703	1,695	7,915		7,861		50	31
Total liabilities	$ 60,214	[3]	$ 56,984	[3]		$ 2,594	$ 2,000	$ 658	$ 30,693	[4]	$ 28,490	[4]	$ 2,338	$ 362	$ 5,214	[5]	$ 5,306	[5]	$ 237	$ 269

[1] Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.

[2] Includes total assets of $6.0 billion and total liabilities of $2.0 billion due to the consolidation of CENG beginning April 1, 2014. See Note 6 — Investment in Constellation Energy Nuclear Group, LLC for additional information.

[3] Exelon’s consolidated assets include $7,773 million and $1,755 million at September 30, 2014 and December 31, 2013, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $2,594 million and $658 million at September 30, 2014 and December 31, 2013, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 - Variable Interest Entities.

[4] Generation’s consolidated assets include $7,703 million and $1,695 million at September 30, 2014 and December 31, 2013, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $2,338 million and $362 million at September 30, 2014 and December 31, 2013, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 - Variable Interest Entities.

[5] BGE’s consolidated assets include $50 million and $31 million at September 30, 2014 and December 31, 2013, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $237 million and $269 million at September 30, 2014 and December 31, 2013, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 - Variable Interest Entities.