Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended		12 Months Ended																																									1 Months Ended	6 Months Ended																3 Months Ended		6 Months Ended
	Jun. 30, 2014 VIE		Dec. 31, 2013 VIE		Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2014 Commercial Agreement Variable Interest Entities [Member]		Dec. 31, 2013 Commercial Agreement Variable Interest Entities [Member]		Jun. 30, 2014 Equity Method Investment Variable Interest Entities [Member]		Dec. 31, 2013 Equity Method Investment Variable Interest Entities [Member]		Jun. 30, 2014 Investments [Member]	Dec. 31, 2013 Investments [Member] Maximum [Member]	Dec. 31, 2013 Investments [Member] Maximum [Member] Commercial Agreement Variable Interest Entities [Member]	Jun. 30, 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]	Jun. 30, 2014 Contract Intangible Asset [Member]	Dec. 31, 2013 Contract Intangible Asset [Member] Maximum [Member]	Jun. 30, 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]	Jun. 30, 2014 Payment Guarantee [Member]	Dec. 31, 2013 Payment Guarantee [Member] Maximum [Member]	Jun. 30, 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]	Jun. 30, 2014 Net assets pledged for Zion Station decommissioning		Dec. 31, 2013 Net assets pledged for Zion Station decommissioning	Dec. 31, 2013 Net assets pledged for Zion Station decommissioning Maximum [Member]		Jun. 30, 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]		Jun. 30, 2014 VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember	Dec. 31, 2013 VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember	Jun. 30, 2013 VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember	Jun. 30, 2014 Exelon Generation Co L L C [Member]	Dec. 31, 2013 Exelon Generation Co L L C [Member]	Jun. 30, 2013 Exelon Generation Co L L C [Member]	Dec. 31, 2012 Exelon Generation Co L L C [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] CENGMember [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] CENGMember [Member]	Jun. 30, 2014 Exelon Generation Co L L C [Member] VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember	Dec. 31, 2013 Exelon Generation Co L L C [Member] VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember	Jun. 30, 2013 Exelon Generation Co L L C [Member] VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember	Jun. 30, 2014 Commonwealth Edison Co [Member]	Dec. 31, 2013 Commonwealth Edison Co [Member]	Jun. 30, 2013 Commonwealth Edison Co [Member]	Dec. 31, 2012 Commonwealth Edison Co [Member]	Jun. 30, 2014 PECO Energy Co [Member]	Dec. 31, 2013 PECO Energy Co [Member]	Jun. 30, 2013 PECO Energy Co [Member]	Dec. 31, 2012 PECO Energy Co [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member]	Dec. 31, 2013 Baltimore Gas and Electric Company [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member]	Dec. 31, 2012 Baltimore Gas and Electric Company [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Jun. 30, 2013 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] RSB Bond Co LLC [Member]	Jun. 30, 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]	Jun. 30, 2014 Baltimore Gas and Electric Company [Member] VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember	Dec. 31, 2013 Baltimore Gas and Electric Company [Member] VariableInterestEntityPrimaryBeneficiaryAggregatedDisclosureMember
Consolidated Variable Interest Entities Disclosure [Abstract]
Current Assets	$ 991		$ 484																																					$ 956	$ 446																$ 28	$ 28
Non Current Assets	7,426		1,905																																					7,407	1,884																3								3
Total Assets	8,417		2,389																																					8,363	2,330																31	31
Current Liabilities	815		566																																					732	481																76	74
Non Current Liabilites	2,911		774																																					2,738	562																158	195
Total Liabilities	3,726		1,340																																					3,470	1,043																234	269
Deferred tax assets	0				0																																			0	0
Remittance of payments received from customers for rate stabilization to BondCo.																																																													21	17	42	39
Parental guarantee provided	75		75																																									7	7
Severance Costs																																													6
RestructuringAndRelatedCostExpectedCostRemaining																																												4
Other long term liabilities																																												113	113
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	444	[1]	460	[1]			119	[1]	128	[1]	325	[1]	332	[1]
Total liabilities	122	[1]	140	[1]			2	[1]	17	[1]	120	[1]	123	[1]
Our ownership interest	63	[1]	86	[1]							63	[1]	86	[1]
Other ownership interests	259	[1]	234	[1]			117	[1]	111	[1]	142	[1]	123	[1]
Our maximum exposure to loss															73	74	7	73	67	9	9	9	9	3	5	3	5	45	[2]		44	[2]	45	[2]	44	[2]
Variable Interest Entity Nonconsolidated Carrying Amount Assets Liabilities And Other Information Footnotes [Abstract]
Gross pledged assets	486		614																																					402	458
Pledged assets liabilities offset	443		414																																					385	414
Statement of Financial Position [Abstract]
Restricted Cash and Cash Equivalents, Current																																					75	80		88	71					47	52		4	2			2	2			58	28								28	28
Accounts Receivable, Net, Current	2,973		2,981																																		296	260		1,733	1,689					296	260		516	451			304	360			419	480
Cash and Cash Equivalents, at Carrying Value	1,362		1,609		991	1,486																															126	62		305	1,258	222	671			126	62		38	36	93	144	93	217	56	362	15	31	457	89
Other Receivables	1,005		1,175																																		133			441	353					133			428	584			107	107			102	114
Energy Related Inventory, Other Fossil Fuel	409		276																																		103	2		328	164					103	2						34	60			48	53
Inventory, Raw Materials and Supplies	1,041		829																																		165			872	671					165							25	21			33	28
Other Assets Current	775		666																																		61	53		524	505					54	42		32	29			51	36			8	7
Assets, Current	9,823		10,137																																		959	457		5,727	6,439					924	418		1,434	1,540			803	906			916	1,011								28	28
Property, plant and equipment, net	51,747		47,330																																		4,603	1,171		23,743	20,111					4,603	1,171		15,121	14,666			6,545	6,384			6,030	5,864
Decommissioning Fund Investments	10,437		8,071																																		2,030			10,437	8,071					2,030
Goodwill	2,674		2,625																																		48			49	0					48			2,625	2,625
Other Assets Noncurrent	1,092		964																																		125	127		687	645					106	106		275	291			38	38			24	26								3	3
Total Deferred Debits And Other Assets	22,086		22,457																											1,298							6,806			14,952	14,682					6,787	1,277		7,989	7,912			2,413	2,327			931	986								3	3
Assets	83,656		79,924																																		7,765	1,755		44,422	41,232					7,711	1,695		24,544	24,118			9,761	9,617			7,877	7,861								31	31
Short-term Borrowings	621		341																																		40			53	22					40	5		498	184							70	135
Long-term Debt and Capital Lease Obligations, Current	2,047		1,509																																		84		85	52	561					5			260	617			250	250			72	70								72	70
Accounts Payable, Current	2,633		2,484																																		243	170		1,508	1,322					243	170		505	449			298	285			205	270
Derivative Liabilities Current	228		159																																		24	29		215	142					24			13	17
Energy Marketing Contract Liabilities, Current	239		261																																					233	249					12	29
Other Liabilities Current	994		858																																		165	5		473	389					165	5		82	72			32	37			61	35
Liabilities, Current	8,567		7,728																																		657	320		4,215	3,867					575	236		2,080	2,048			922	891			747	827								76	74
Long-term Debt, Excluding Current Maturities	18,133		17,623																																		258	298		5,944	5,645					84	86		5,448	5,058			1,947	1,947			1,904	1,941								158	195
Asset Retirement Obligations, Noncurrent	7,054		5,194																																		1,731			6,907	5,047					1,731			100	99			30	29			17	19
Defined Benefit Pension Plan, Liabilities, Noncurrent	1,804		1,876																																		133			125						133
Energy Marketing Contract Liabilities, Noncurrent	260		266																									18									12	12	5	260		266				18	12	5
Other Liabilities Noncurrent	2,133		2,540																																		178	28		761	811					178	28		841	994			92	99			65	67
Total Deferred Credits And Other Liabilities	32,079		30,985																																		2,454	338		19,665	17,455					2,280	126		9,112	9,278			3,630	3,530			2,313	2,280								158	195
Liabilities	59,427		56,984																																		3,111	658		30,772	28,490					2,855	362		16,846	16,590			6,683	6,552			5,222	5,306								234	269
Accrued Liabilities, Current	1,382		1,633																																		89	26		819	976					86	22		274	307			167	106			95	111								4	4
Other Postretirement Defined Benefit Plan, Liabilities, Noncurrent	$ 1,419		$ 2,190																																		$ 136			$ 941	$ 850					$ 136			$ 284	$ 381			$ 292	$ 286			$ 215	$ 217

[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 $402 million and $458 million as of June 30, 2014 and December 31, 2013, respectively; offset by payables to ZionSolutions LLC of $357 million and $414 million as of June 30, 2014 and December 31, 2013, respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE.