Debt and Credit Agreements - Summary of Bank Commitments, Credit Facility Borrowings and Available Capacity (Details) - USD ($) $ in Millions		Dec. 31, 2016	Sep. 30, 2016	May 26, 2016		Apr. 01, 2016	Jan. 05, 2016	Dec. 31, 2015	Oct. 23, 2015	Aug. 10, 2013	Aug. 01, 2011
Short-term Debt [Line Items]
Facility draws		$ 75
Outstanding letters of credit	[1]	1,510
Actual available capacity		7,915
To Support Additional Commercial Paper	[2]	7,108
Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 600	[3]					$ 500
Exelon Corporate [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	29
Actual available capacity		571
To Support Additional Commercial Paper	[2]	571
Exelon Generation Co L L C [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit		1,170
Actual available capacity		4,130
To Support Additional Commercial Paper		3,510
Credit facility agreements with minority and community banks		50
Exelon Generation Co L L C [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		500						$ 275
Exelon Generation Co L L C [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		7
Exelon Generation Co L L C [Member] | Line of Credit [Member]
Short-term Debt [Line Items]
Maximum Program Size						$ 200	$ 150		$ 100
Actual available capacity		119
To Support Additional Commercial Paper	[2]	0
Commonwealth Edison Co [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	2
Actual available capacity		998
To Support Additional Commercial Paper	[2]	998
Credit facility agreements with minority and community banks		34
Commonwealth Edison Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		12
PECO Energy Co [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	2
Actual available capacity		598
To Support Additional Commercial Paper	[2]	598
Credit facility agreements with minority and community banks		34
PECO Energy Co [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		21
Baltimore Gas and Electric Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	0
Actual available capacity		600
To Support Additional Commercial Paper	[2]	555
Credit facility agreements with minority and community banks		5
Baltimore Gas and Electric Company [Member] | Letter of Credit [Member]
Short-term Debt [Line Items]
Outstanding letters of credit		2
Pepco Holdings LLC [Member] | Revolving Credit Facility [Member]
Short-term Debt [Line Items]
Maximum Program Size				$ 900							$ 1,500
Credit facility agreements with minority and community banks			$ 900
Potomac Electric Power Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	0
Actual available capacity		300
To Support Additional Commercial Paper	[2]	277
Delmarva Power and Light Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	0
Actual available capacity		300
To Support Additional Commercial Paper	[2]	300
Credit facility agreements with minority and community banks		2
Atlantic City Electric Company [Member]
Short-term Debt [Line Items]
Facility draws		0
Outstanding letters of credit	[1]	1
Actual available capacity		299
To Support Additional Commercial Paper	[2]	299
Credit facility agreements with minority and community banks		$ 2

[1] Excludes nonrecourse debt letters of credit, see discussion below on Continental Wind.

[2] Pepco, DPL and ACE's revolving credit facility is subject to available borrowing capacity. The borrowing capacity may be increased or decreased during the term of the facility, except that (i) the sum of the borrowing capacity must equal the total amount of the facility, and (ii) the aggregate amount of credit used at any given time by each of Pepco, DPL or ACE may not exceed $900 million or the maximum amount of short-term debt the company is permitted to have outstanding by its regulatory authorities. The total number of the borrowing reallocations may not exceed eight per year during the term of the facility.

[3] Excludes additional credit facility agreements for Generation, ComEd, PECO, BGE, Pepco, DPL and ACE with aggregate commitments of $50 million, $34 million, $34 million ,$5 million, $2 million, $2 million and $2 million, respectively, arranged with minority and community banks located primarily within utilities' service territories. These facilities expire on October 13, 2017. These facilities are solely utilized to issue letters of credit. As of December 31, 2016, letters of credit issued under these facilities totaled $7 million, $12 million, $21 million and $2 million for Generation, ComEd, PECO and BGE, respectively.