Supplemental Financial Information - Narrative (Details) (PECO Energy Co [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2015
Supplemental Financial Information Tables [Line Items]
Smart Grid Grant Project Capital Expenditures	$ 2
Smart Grid Grant Reimbursements	2exc_SmartGridGrantReimbursements
Financing Receivable, Net		14us-gaap_NotesReceivableNet
Financing Receivable, Allowance for Credit Losses	15	14
Low To Medium Risk [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	1	1
Risk Level, Medium [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	3	4
Risk Level, High [Member]
Supplemental Financial Information Tables [Line Items]
Financing Receivable, Net	$ 11	$ 9

Represents the reimbursable smart grid investment grant project expenditures included in capital expenditures.

No definition available.

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Period Type:	duration

- Definition

DOE Smart Grid Investment Grant Reimbursement

+ References

No definition available.

+ Details

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Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 11B

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=49124121&loc=SL6953423-111524

+ Details

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- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.3)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Period Type:	instant

- Details

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- Details

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- Details

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