Balance of gain (loss) in AOCI related to cash flow hedging instruments.

No definition available.

Name:	exc_CashFlowHedgeAccumulatedOtherComprehensiveIncomeGainLoss
Namespace Prefix:	exc_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The amount of net gains (losses) on a cash flow hedge reclassified in the period to earnings from accumulated other comprehensive income related to treasury rate locks, net of tax effect.

+ References

No definition available.

+ Details

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- Definition

Changes to accumulated comprehensive income resulting from gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. A cash flow hedge is a hedge of the exposure to variability in the cash flows of a recognized asset or liability or a forecasted transaction that is attributable to a particular risk.

+ References

No definition available.

+ Details

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

- Details

Name:	exc_EffectofHedgesonAccumulatedOtherComprehensiveIncomeRollForward
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- Definition

The amount of net gains (losses) on a cash flow hedge reclassified in the period to earnings from accumulated other comprehensive income related to a swap contract with a related party, net of tax effect.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain or loss excluded from AOCI related to settled interest rate swaps and treasury rate locks.

+ References

No definition available.

+ Details

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

- Definition

Revenue from generation of electricity, a process of producing electric energy by transforming other forms of energy such as nuclear, fossil fuel, solar, geothermal, hydro, and wind.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.1(b))

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Definition

The net gain (loss) recognized in earnings during the reporting period representing the amount of the cash flow hedges' ineffectiveness.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (d)(1)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

+ Details

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- Definition

Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e637-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=28358780&loc=d3e689-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph c

-URI http://asc.fasb.org/extlink&oid=7476318&loc=d3e41638-113959

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Derivative Financial Instruments - Summary of AOCI related to Cash Flow Hedges (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Ineffective portion recognized in income	$ 18	$ 2
Net gain (loss) of reclassifications from accumulated OCI to net income related to the settlements of swap contract			133
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	78	270
Net gains (losses) related to interest rate swaps and treasury rate locks	20	5
Net gain (loss) related to effective portion of changes in fair value of treasury rate locks	15	15
Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income	16,614	14,207	12,735
Total Cash Flow Hedges [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated OCI derivative gain - Beginning Balance	120	368
Effective portion of changes in fair value	(31)	29
Accumulated OCI derivative gain - Ending Balance	(28)	120
Total Cash Flow Hedges [Member] \| Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Accumulated OCI derivative gain - Beginning Balance	119	532
Effective portion of changes in fair value	0	0
Accumulated OCI derivative gain - Ending Balance	2	119
Operating Revenue One [Member] \| Energy Related Hedges [Member] \| Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Net gain (loss) of reclassifications from accumulated OCI to net income related to the settlements of swap contract		133
Operating Revenue One [Member] \| Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Total Cash Flow Hedges [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income	(117)	(277)
Operating Revenue One [Member] \| Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] \| Reclassification out of Accumulated Other Comprehensive Income [Member] \| Total Cash Flow Hedges [Member] \| Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Reclassifications from accumulated OCI to net income	(117)	(413)
Purchased PowerOne [Member] \| Total Cash Flow Hedges [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Ineffective portion recognized in income		0
Purchased PowerOne [Member] \| Total Cash Flow Hedges [Member] \| Exelon Generation Co L L C [Member]
Effect of Hedges on Accumulated Other Comprehensive Income [Roll Forward]
Ineffective portion recognized in income		$ 0