Debt and Credit Agreements - Issuance of Long-Term Debt (Details) - USD ($)	3 Months Ended
Jun. 30, 2017	Jun. 30, 2014
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.497%	2.50%
JSNotes350June2022 [Member] \| Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Interest Rate	3.50%
Debt Instrument, Face Amount	$ 1,150,000,000
Exelon Generation Co L L C [Member] \| EEPFNotes372April2018 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.72%
Debt Instrument, Face Amount	$ 3,000,000
Exelon Generation Co L L C [Member] \| EEPF261Sep2018 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	2.61%
Debt Instrument, Face Amount	$ 6,000,000
Exelon Generation Co L L C [Member] \| EEPFNotes390Jan2018 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.90%
Debt Instrument, Face Amount	$ 12,000,000
Exelon Generation Co L L C [Member] \| AGEPFNotesNov2017 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 13,000,000
Debt Instrument, Interest Rate Terms	LIBOR + 1.25%
Exelon Generation Co L L C [Member] \| SeniorUnsecured295Jan2020 [Member] \| Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Interest Rate	2.95%
Debt Instrument, Face Amount	$ 250,000,000
Exelon Generation Co L L C [Member] \| EEPF353Apr2019 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.53%
Debt Instrument, Face Amount	$ 8,000,000
Exelon Generation Co L L C [Member] \| SeniorUnsecured340Mar2022 [Member] \| Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Interest Rate	3.40%
Debt Instrument, Face Amount	$ 500,000,000
Exelon Generation Co L L C [Member] \| EGTP475Sep2021 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 6,000,000
Debt Instrument, Interest Rate Terms	LIBOR + 4.75%
Potomac Electric Power Company [Member] \| FMB415Mar2043 [Member] \| First Mortgage [Member]
Debt Instrument [Line Items]
Interest Rate	4.15%
Debt Instrument, Face Amount	$ 200,000,000
Potomac Electric Power Company [Member] \| EEPFNotes330December2017 [Member] \| Long-term Debt [Member]
Debt Instrument [Line Items]
Interest Rate	3.30%
Debt Instrument, Face Amount	$ 1,000,000

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Description of the interest rate as being fixed or variable, and, if variable, identification of the index or rate on which the interest rate is based and the number of points or percentage added to that index or rate to set the rate, and other pertinent information, such as frequency of rate resets.

+ References

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Balance Type:	na
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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