Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended	0 Months Ended	6 Months Ended						6 Months Ended																	0 Months Ended				6 Months Ended					6 Months Ended																6 Months Ended										6 Months Ended
	Jun. 30, 2011 MW Tons Months	Jun. 06, 2011 Exelon Generation Co L L C [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] Tons GWH BasisPoints OpenClaims	Dec. 31, 2010 Exelon Generation Co L L C [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2010 Exelon Generation Co L L C [Member] Total Accrual For Environmental Loss Contingencies [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2010 Exelon Generation Co L L C [Member] Accrual For MGP Investigation And Remediation [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Four And Within Five Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Four And Within Five Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Four And Within Five Years From Balance Sheet Date [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Five Years From Balance Sheet Date And Thereafter [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than Five Years From Balance Sheet Date And Thereafter [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] More Than One And Within Five Years From Balance Sheet Date [Member]	Feb. 09, 2007 Exelon Generation Co L L C [Member] Teg Tep [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] Teg Tep [Member]	Jun. 30, 2011 Exelon Generation Co L L C [Member] Sithe [Member]	Jan. 31, 2005 Exelon Generation Co L L C [Member] Sithe [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] SmartMeters BasisPoints MGPSites	Jun. 30, 2011 Commonwealth Edison Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2010 Commonwealth Edison Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2010 Commonwealth Edison Co [Member] Accrual For MGP Investigation And Remediation [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than One And Within Three Years From Balance Sheet Date Member	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than Two And Within Three Years From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than Three And Within Four Years From Balance Sheet Date [Member]	Jun. 30, 2011 Commonwealth Edison Co [Member] More Than Four And Within Five Years From Balance Sheet Date [Member]	Jun. 30, 2011 PECO Energy Co [Member] MW BasisPoints MGPSites SmartMeters	Jun. 30, 2011 PECO Energy Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2010 PECO Energy Co [Member] Total Accrual For Environmental Loss Contingencies [Member]	Jun. 30, 2011 PECO Energy Co [Member] Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2010 PECO Energy Co [Member] Accrual For MGP Investigation And Remediation [Member]	Jun. 30, 2011 PECO Energy Co [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 PECO Energy Co [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 PECO Energy Co [Member] One Year From Balance Sheet Date [Member]	Jun. 30, 2011 PECO Energy Co [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 PECO Energy Co [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 PECO Energy Co [Member] More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 Total Accrual For Environmental Loss Contingencies [Member]	Dec. 31, 2010 Total Accrual For Environmental Loss Contingencies [Member]	Jun. 30, 2011 Accrual For MGP Investigation And Remediation [Member]	Dec. 31, 2010 Accrual For MGP Investigation And Remediation [Member]	Jun. 30, 2011 One Year From Balance Sheet Date [Member]	Jun. 30, 2011 One Year From Balance Sheet Date [Member]	Jun. 30, 2011 More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 More Than One And Within Two Years From Balance Sheet Date [Member]	Jun. 30, 2011 More Than Two And Within Three Years From Balance Sheet Date [Member]	Jun. 30, 2011 More Than Two And Within Three Years From Balance Sheet Date [Member]	Jun. 30, 2011 More Than Three And Within Four Years From Balance Sheet Date [Member]	Jun. 30, 2011 More Than Three And Within Four Years From Balance Sheet Date [Member]	Jun. 30, 2011 More Than Four And Within Five Years From Balance Sheet Date [Member]	Jun. 30, 2011 More Than Five Years From Balance Sheet Date And Thereafter [Member]
Accrual For Environmental Loss Contingencies [Line Items]
Accrued environmental liabilities					$ 16	$ 15	$ 0	$ 0																							$ 118	$ 120	$ 112	$ 114													$ 47	$ 44	$ 44	$ 42							$ 181	$ 179	$ 156	$ 156
Increase Decrease In Regulatory Construction Commitments [Abstract]
Changes in construction commitments																																				44		8			1		10		(12)
Increase Decrease In Letters Of Credit And Guarantees [Abstract]
Change in letters of credit	(84)		(79)																											(5)
Change in guarantees	173		177																																																											(11)		195		(95)		96		(12)
Increase Decrease In Unrecorded Unconditional Purchase Obligation [Abstract]
Increase (decrease) in other purchase obligations									71		67			49			49			32															(23)					1											20			10							65		75		46		49		32
Guarantees Related To Sithe [Abstract]
Acquisition of interest in subsidiary																													50.00%
Sale of interest in subsidiary																										49.50%			100.00%
Maximum exposure related to guarantees																											95	200
Guarantees Related To TEG TEP [Abstract]
Proceeds from sale of equity method investments																										95
MGP Site Contingency [Abstract]
Total number of MGP sites																														42																27
Approved clean-up																														12																16
Sites under study/remediation																														27																9
MGP reserve update																																														5
Environmental Loss Contingency Estimate [Abstract]
Low end of range of cooling tower cost	430		430
Section 316(b) of the Clean Water Act [Abstract]
Incremental expense related to change in plant useful life			7
Employee retention payments			1						14
Annual employee retention expense																									3
Conemaugh Station Water Discharge [Abstract]
Percentage Of Ownership Conemaugh		21.00%
Total Conemaugh Station water discharge settlement to be paid by all responsible parties		5
Portion of Conemaugh Station water discharge settlement to be paid by Exelon		1
Site Contingency Shared Liability [Abstract]
Tons of soil disposed			39,000
Tons of leached barium sulfate contained in disposed soil			8,700
Total cost of remediation to be shared by PRPs			42
Emission Credits or Allowances [Abstract]
SO2 emissions allowance impairment			4
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Net investment in long-term direct financing leases			642
GHG emissions regulation [Abstract]
Minimum GHG emissions by stationary sources to qualify for regulation	100,000
Minimum additional GHG emissions by stationary sources after a modification	75,000
Asbestos Loss Contingency [Abstract]
Asbestos liability reserve			53	53
Asbestos liability reserve related to open claims			15
Open asbestos liability claims			175
Asbestos liability reserve related to anticipated claims			38
Increase Decrease In Future Energy Sales Commitments [Abstract]
Increase (decrease) in future energy Sales Commitments to third parties			626									445			431			165			54		168
Current year energy sales to third parties			(637)
Increase Decrease In Future Energy Purchase Commitments [Abstract]
Increase (decrease) in future energy purchase commitments from third parties			(478)									(38)			(39)			(42)			(37)		(141)														178		192			292		179								19			46
Fulfillment of energy purchase commitments			(181)
Change In Fuel And Natural Gas Purchase Obligations [Abstract]
Change In natural gas purchase commitments																																														52							38			14
Increase (decrease) in future fuel purchase commitments			$ (766)							$ (667)			$ 46			$ (5)			$ (25)			$ (37)		$ (78)