Supplemental Financial Information (Details) (USD $) In Millions	3 Months Ended				6 Months Ended				12 Months Ended		19 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010		Dec. 31, 2010		Jun. 30, 2011		Dec. 09, 2010
Accrued Liabilities Current [Abstract]
Total accrued expenses	$ 878				$ 878				$ 1,040		$ 878
Accumulated Other Comprehensive Income (Loss) [Abstract]
Net unrealized gain (loss) on cash flow hedges	209				209				400		209
Pension and non-pension postretirement benefit plans	(2,719)				(2,719)				(2,823)		(2,719)
Accumulated unrealized gain (loss) on marketable securities	1				1				0		1
Accumulated other comprehensive income (loss), net	(2,509)				(2,509)				(2,423)		(2,509)
Property, Plant And Equipment [Abstract]
Accumulated depreciation	10,490	[1]			10,490	[1]			10,064	[2]	10,490	[1]
Accounts receivable, net
Allowance for uncollectible accounts	229				229				228		229
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefits costs					271		288
Provision for uncollectible accounts					45		38
Stock-based compensation costs					43		27
Other decommissioning-related activity					(35)	[3]	31	[3]
Energy-related options					68	[4]	(36)	[4]
Amortization of regulatory asset related to debt costs					11		12
Accrual for Illinois utility distribution tax refund							25	[5]
Under-recovered uncollectible accounts					13		(49)	[6]
Inventory write down related to plant retirements											17
Discrete impacts from 2010 Rate Case Order					(32)
Other					(6)		(8)
Total other non-cash operating activities					378		278
Other Non-Cash Operating Activities Footnotes [Abstract]
Accrual for Illinois utility distribution tax refund							25	[5]
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs					(99)		60
Other current assets					(216)		(172)
Other noncurrent assets and liabilities					68		103
Total changes in other assets and liabilities					(247)		(9)
Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract]
Exelon Wind acquisition	32				32						32		(32)
Repurchase Agreements [Abstract]
Proceeds from nuclear decommissioning trust fund sales					1,657		1,799
Investment in nuclear decommissioning trust funds					(1,772)		(1,897)
Supplemental Financial Information Textuals Abstract
Payment to IRS									302
Operating revenues [Abstract]
Total operating revenues	4,587		4,398		9,638		8,859
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	316		279		629		558
Regulatory assets	13		240	[7]	27		475	[7]
Nuclear fuel	181	[8]	168	[8]	355	[8]	323	[8]
Asset retirement obligation accretion	52	[9]	50	[9]	103	[9]	99	[9]
Total depreciation, amortization and accretion	562		737		1,114		1,455
Total taxes other than income	191		186		394		383
Equity Method Investment Summarized Financial Information Gross Profit Loss [Abstract]
Total income (loss) in equity method investments	0		0		0		0
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	38	[10]	49	[10]	81	[10],[11]	98	[10]
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	16	[10]	14	[10]	26	[10],[11]	26	[10]
Net unrealized losses on decommissioning trust funds - Regulatory Agreement Units	28		(318)		140		(207)
Net unrealized losses on decommissioning trust funds - Non-Regulatory Agreement	11		(94)		54		(59)
Regulatory offset to decommissioning trust fund-related activities	(70)	[11]	215	[11]	(221)	[11]	87	[11]
Net unrelaized losses on pledged assets	22				45
Total decommissioning-related activities	45		(134)		125		(55)
Investment income	1				2
Long-term lease income	7		7		14		13
Interest income related to uncertain income tax positions	43		0		46		0
AFUDC - equity	4				9
Other	0		5		(2)		13
Other, net	100		(122)		194		(29)
Exelon Generation Co L L C [Member]
Capital Leases, Net Investment in Direct Financing Leases [Abstract]
Net investment in long-term leases	642				642						642
Accrued Liabilities Current [Abstract]
Total accrued expenses	562				562				391		562
Accumulated Other Comprehensive Income (Loss) [Abstract]
Net unrealized gain (loss) on cash flow hedges	690				690				1,013		690
Pension and non-pension postretirement benefit plans	0				0				0		0
Accumulated unrealized gain (loss) on marketable securities	0				0				0		0
Accumulated other comprehensive income (loss), net	690				690				1,013		690
Property, Plant And Equipment [Abstract]
Accumulated depreciation	5,080	[1]			5,080	[1]			4,880	[2]	5,080	[1]
Accounts receivable, net
Allowance for uncollectible accounts	30				30				32		30
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefits costs					123		134
Provision for uncollectible accounts					0		1
Stock-based compensation costs					0		0
Other decommissioning-related activity					(35)	[3]	31	[3]
Energy-related options					68	[4]	(36)	[4]
Amortization of regulatory asset related to debt costs					0		0
Accrual for Illinois utility distribution tax refund							0
Under-recovered uncollectible accounts					0		0	[6]
Inventory write down related to plant retirements											17
Other					12		3
Total other non-cash operating activities					168		133
Other Non-Cash Operating Activities Footnotes [Abstract]
Accrual for Illinois utility distribution tax refund							0
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs					0		0
Other current assets					(91)		(57)
Other noncurrent assets and liabilities					(17)		23
Total changes in other assets and liabilities					(108)		(34)
Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract]
Exelon Wind acquisition	32				32						32		(32)
Repurchase Agreements [Abstract]
Proceeds from nuclear decommissioning trust fund sales					1,657		1,799
Investment in nuclear decommissioning trust funds					(1,772)		(1,897)
Operating revenues [Abstract]
Total operating revenues	2,546		2,353		5,285		4,773
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	138		115		277		223
Regulatory assets	0		0		0		0	[7]
Nuclear fuel	181	[8]	168	[8]	355	[8]	323	[8]
Asset retirement obligation accretion	52	[9]	49	[9]	103	[9]	99	[9]
Total depreciation, amortization and accretion					735		645
Total taxes other than income	66		61		132		118
Equity Method Investment Summarized Financial Information Gross Profit Loss [Abstract]
Total income (loss) in equity method investments	0		0		0		0
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units	38	[10]	49	[10]	81	[10],[11]	98	[10]
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units	16	[10]	14	[10]	26	[10],[11]	26	[10]
Net unrealized losses on decommissioning trust funds - Regulatory Agreement Units	28		(318)		140		(207)
Net unrealized losses on decommissioning trust funds - Non-Regulatory Agreement	11		(94)		54		(59)
Regulatory offset to decommissioning trust fund-related activities	(70)	[11]	215	[11]	(221)	[11]	87	[11]
Net unrelaized losses on pledged assets	22				45
Total decommissioning-related activities	45		(134)		125		(55)
Investment income	0				0
Long-term lease income	0		0		0		0
Interest income related to uncertain income tax positions	33		0		33		0
AFUDC - equity	0				0
Other	(2)		1		(6)		1
Other, net	76		(133)		152		(54)
Commonwealth Edison Co [Member]
Accrued Liabilities Current [Abstract]
Total accrued expenses	260				260				366		260
Accumulated Other Comprehensive Income (Loss) [Abstract]
Net unrealized gain (loss) on cash flow hedges	0				0				0		0
Pension and non-pension postretirement benefit plans	0				0				0		0
Accumulated unrealized gain (loss) on marketable securities	(1)				(1)				(1)		(1)
Accumulated other comprehensive income (loss), net	(1)				(1)				(1)		(1)
Property, Plant And Equipment [Abstract]
Accumulated depreciation	2,592				2,592				2,428		2,592
Accounts receivable, net
Allowance for uncollectible accounts	78				78				80		78
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefits costs					108		106
Provision for uncollectible accounts					18		16
Stock-based compensation costs					0		0
Other decommissioning-related activity					0	[3]	0	[3]
Energy-related options					0	[4]	0	[4]
Amortization of regulatory asset related to debt costs					9		11
Accrual for Illinois utility distribution tax refund							25	[5]
Under-recovered uncollectible accounts					13		(49)	[6]
Discrete impacts from 2010 Rate Case Order					(32)
Other					(1)		1
Total other non-cash operating activities					115		60
Other Non-Cash Operating Activities Footnotes [Abstract]
Accrual for Illinois utility distribution tax refund							25	[5]
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs					(82)		44
Other current assets					(13)		10
Other noncurrent assets and liabilities					133		41
Total changes in other assets and liabilities					38		95
Operating revenues [Abstract]
Total operating revenues	1,444		1,499		2,910		2,914
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	126		117		248		234
Regulatory assets	10		14		22		27	[7]
Nuclear fuel	0		0		0	[8]	0	[8]
Asset retirement obligation accretion	0		0		0	[9]	0	[9]
Total depreciation, amortization and accretion					270		261
Total taxes other than income	70		44		147		107
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units			0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units			0
Net unrealized losses on decommissioning trust funds - Regulatory Agreement Units			0
Net unrealized losses on decommissioning trust funds - Non-Regulatory Agreement			0
Regulatory offset to decommissioning trust fund-related activities			0
Total decommissioning-related activities			0
Investment income	0				0
Long-term lease income	0		0		0		0
Interest income related to uncertain income tax positions	1		2		1		2
AFUDC - equity	2				4
Other	1		6		3		9
Other, net	4		8		8		11
PECO Energy Co [Member]
Accrued Liabilities Current [Abstract]
Total accrued expenses	77				77				95		77
Accumulated Other Comprehensive Income (Loss) [Abstract]
Net unrealized gain (loss) on cash flow hedges	0				0				0		0
Pension and non-pension postretirement benefit plans	0				0				0		0
Accumulated unrealized gain (loss) on marketable securities	0				0				0		0
Accumulated other comprehensive income (loss), net	0				0				0		0
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables	24				24				22		24
Installment plan receivables uncollectible accounts reserve	21				21				19		21
Property, Plant And Equipment [Abstract]
Accumulated depreciation	2,595				2,595				2,531		2,595
Accounts receivable, net
Allowance for uncollectible accounts	121				121				116		121
Other Non-Cash Operating Activities [Abstract]
Pension and non-pension postretirement benefits costs					16		24
Provision for uncollectible accounts					27		21
Stock-based compensation costs					0		0
Other decommissioning-related activity					0	[3]	0	[3]
Energy-related options					0	[4]	0	[4]
Amortization of regulatory asset related to debt costs					2		2
Accrual for Illinois utility distribution tax refund							0
Under-recovered uncollectible accounts					0		0	[6]
Other					(1)		(3)
Total other non-cash operating activities					44		44
Other Non-Cash Operating Activities Footnotes [Abstract]
Accrual for Illinois utility distribution tax refund							0
Changes In Other Assets and Liabilities [Abstract]
Under/over-recovered energy and transmission costs					(17)		16
Other current assets					(104)	[12]	(127)	[12]
Other noncurrent assets and liabilities					13		37
Total changes in other assets and liabilities					(108)		(74)
DOE Smart Grid Investment Grant [Abstract]
Amount included in capital expenditures	19				19						19
Smart Grid Grant Reimbursements	26				26						26
Operating revenues [Abstract]
Total operating revenues	842		1,269		1,996		2,724
Depreciation, Amortization and Accretion [Abstract]
Property, plant and equipment	47		42		93		85
Regulatory assets	3		226	[7]	5		448	[7]
Nuclear fuel	0		0		0	[8]	0	[8]
Asset retirement obligation accretion	0		0		0	[9]	0	[9]
Total depreciation, amortization and accretion					98		533
Total taxes other than income	51		77		106		150
Equity Method Investment Summarized Financial Information Gross Profit Loss [Abstract]
Total income (loss) in equity method investments	0		0		0		0
Decommissioning-Related Activities [Abstract]
Net realized income on decommissioning trust funds - Regulatory Agreement Units			0
Net realized income on decommissioning trust funds - Non-Regulatory Agreement Units			0
Net unrealized losses on decommissioning trust funds - Regulatory Agreement Units			0
Net unrealized losses on decommissioning trust funds - Non-Regulatory Agreement			0
Regulatory offset to decommissioning trust fund-related activities			0
Total decommissioning-related activities			0
Investment income	1				2
Long-term lease income	0		0		0		0
Interest income related to uncertain income tax positions	0				1		0
AFUDC - equity	2				6
Other	0		(1)		(1)		4
Other, net	3		(1)		8		4
PECO Energy Co [Member] | Low Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	0				0				0		0
PECO Energy Co [Member] | Low To Medium Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	1				1				1		1
PECO Energy Co [Member] | Medium Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	4				4				5		4
PECO Energy Co [Member] | High Risk [Member]
Financing Receivable Recorded Investment [Line Items]
Installment plan receivables uncollectible accounts reserve	16				16				13		16
Scenario Previously Reported [Member]
Repurchase Agreements [Abstract]
Proceeds from nuclear decommissioning trust fund sales							12,528
Investment in nuclear decommissioning trust funds							(12,626)
Restatement Adjustment [Member]
Repurchase Agreements [Abstract]
Proceeds from nuclear decommissioning trust fund sales							(10,729)
Investment in nuclear decommissioning trust funds							$ 10,729

[1] Includes accumulated amortization of nuclear fuel in the reactor core of $1,680 million.

[2] Includes accumulated amortization of nuclear fuel in the reactor core of $1,592 million.

[3] Includes the elimination of NDT fund-related activity for the Regulatory Agreement Units, including the elimination of operating revenues, ARO accretion, ARC amortization, investment income and income taxes related to all NDT fund activity for these units. See Note 12 of the 2010 Form 10-K for additional information regarding the accounting for nuclear decommissioning

[4] Includes option premiums reclassified to realized at the settlement of the underlying contracts and recorded to results of operations.

[5] During the second quarter of 2010, ComEd recorded a reduction of $25 million to taxes other than income to reflect management's estimate of future refunds for the 2008 and 2009 tax years associated with Illinois' utility distribution tax based on an analysis of past refunds and interpretations of the Illinois Public Utilities Act. Historically, ComEd has recorded refunds of the Illinois utility distribution tax when received. ComEd believes it now has sufficient, reliable evidence to record and support an estimated receivable associated with the anticipated refund for the 2008 and 2009 tax years.

[6] Includes $70 million of under-recovered uncollectible accounts expense from 2008 and 2009 recoverable prospectively through a rider mechanism as a result of an ICC order issued February 2010. See Note 3 - Regulatory Matters for additional information regarding the Illinois legislation allowing recovery of uncollectible accounts.

[7] For PECO, primarily reflects CTC amortization.

[8] Included in fuel expense on the Registrants' Consolidated Statements of Operations and Comprehensive Income

[9] Included in operating and maintenance expense on the Registrants' Consolidated Statements of Operations and Comprehensive Income.

[10] Includes investment income and realized gains and losses on sales of investments of the trust funds

[11] Includes the elimination of NDT fund-related activity for the Regulatory Agreement Units, including the elimination of net realized income taxes related to all NDT fund activity for those units. See Note 12 of the 2010 Form 10-K for additional information regarding the accounting for nuclear decommissioning

[12] Relates primarily to prepaid utility taxes.