Power Volume

No definition available.

Name:	exc_PowerVolume
Namespace Prefix:	exc_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	duration

- Definition

The proceeds from the sale of an interest in a unit of partnership.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfInterestInPartnershipUnit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

Name:	us-gaap_SubsequentEventLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

All taxes not related to income of the entity or excise or sales taxes levied on the revenue of the entity that are not reported elsewhere. These taxes could include production, real estate, personal property, and pump tax.

+ 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 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

+ Details

Name:	us-gaap_TaxesExcludingIncomeAndExciseTaxes
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=exc_ExGenRenewablesHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Subsequent Event (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
Subsequent Event (Details) $ in Millions	Jul. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) MW	Sep. 30, 2016 USD ($)
Subsequent Event [Line Items]
Power Volume \| MW				220
Taxes, Miscellaneous		$ 456	$ 449	$ 1,313	$ 1,168
ExGen Renewables Holdings, LLC [Member]
Subsequent Event [Line Items]
Proceeds from Sale of Interest in Partnership Unit	$ 400