Aggregate Amount of Capacity, Total

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- Definition

Energy purchase maximum to be purchased

+ Details

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- Definition

Estimated Payment Based On Proportion Of Load, Megawatts

+ Details

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- Definition

Estimated Payment Based on Proportion of Load, Percent

+ Details

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- Definition

The increase (decrease) during the period in the carrying amount of accrued known and estimated losses incurred for which no insurance coverage exists, and for which a claim has been made or is probable of being asserted, typically arising from workmen's' compensation-type of incidents and personal injury to nonemployees from accidents on the entity's property.

+ Details

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- Definition

Long-term Contract for Purchase of Electric Power, Megawatts

+ Details

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- Definition

Maximum Generation Capacity, After Reduction

+ Details

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- Definition

Net power purchases with non-utility generators.

+ Details

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- Definition

Number of purchase power agreements

+ Details

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- Definition

Obligated purchase amount of energy produced at the facility

+ Details

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Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax affect of reclassification adjustment

+ Details

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Balance Type:	debit
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- Definition

Term Of Agreement

+ Details

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- Definition

Cost of electricity purchased and sold during the reporting period.

+ Details

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- Definition

Revenue from the bulk transport of high voltage power, typically over longer distances, between generating plants and distribution systems.

+ Details

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 159
-Paragraph 18
-Subparagraph f

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Principles Board Opinion (APB)
-Number 18
-Paragraph 20
-Subparagraph a (1)

+ Details

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- Definition

The amount of excise and sales taxes included in sales and revenues, which are then deducted as a cost of sales. Includes excise taxes, which are applied to specific types of transactions or items (such as gasoline or alcohol); and sales, use and value added taxes, which are applied to a broad class of revenue-producing transactions involving a wide range of goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 1
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Emerging Issues Task Force (EITF)
-Number 06-3
-Paragraph 4

+ Details

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- Definition

Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

+ Details

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- Definition

The noncurrent portion of the amount recognized for uncertain tax positions as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name FASB Interpretation (FIN)
-Number 48
-Paragraph 6, 7, 8

+ Details

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Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Mar. 31, 2010	Jun. 30, 2011 years mW	Jun. 30, 2010	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007
Electrical transmission revenue	$ (3)
Reduction in self-insurance reserves for general and auto liability claims	4
Term of agreement, years				20
Aggregate amount of capacity				1,949
Taxes included in gross revenues	94	88		190	162
Increase in revenue and pre-tax earnings				2
ACE's share of payment, reflected as a percentage				15.00%
ACE's share of payment, reflected in megawatts				292
Tax affect of reclassification adjustment		1	6		1
Uncertain and effectively settled tax positions	41			41		148	2	3	1
Delmarva Power & Light Co/De [Member] \| Minimum [Member]
Maximum capacity after reduction, in megawatts				38
Delmarva Power & Light Co/De [Member] \| Wind PPA [Member]
Number of purchase power agreements				3
Megawatts received from power purchase agreements (PPAs)				350
Wind PPA [Member]
Purchased energy	4	3		9	6
Delmarva Power & Light Co/De [Member] \| Solar PPA [Member]
Number of purchase power agreements				1
Megawatts received from power purchase agreements (PPAs)				10
Term of agreement, years				20
Obligated purchase amount of energy produced at the facility				70.00%
Atlantic City Electric Co [Member] \| Non-Utility Generators [Member]
Net power purchases with non-utility generators	55	67		112	140
Purchased energy	51	62		104	129
Delmarva Power & Light Co/De [Member]
Purchased energy	145	159		327	360
Energy purchase maximum to be purchased				50.25
Uncertain and effectively settled tax positions	22			22		24
Atlantic City Electric Co [Member]
Purchased energy	$ 196	$ 243		$ 394	$ 478
Equity ownership owned	100.00%			100.00%