Regulatory Matters Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions		9 Months Ended		12 Months Ended
		Sep. 30, 2016		Dec. 31, 2015
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 396		$ 229
Allowance for Doubtful Accounts Receivable		36	[1]	31
Payments to Acquire Other Receivables, Net		$ 360		198
Discount rate		1.00%
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 123		103
Allowance for Doubtful Accounts Receivable		17	[1]	16
Payments to Acquire Other Receivables, Net		106		87
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		90		67
Allowance for Doubtful Accounts Receivable	[2]	7		7
Payments to Acquire Other Receivables, Net		83		60
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		66		59
Allowance for Doubtful Accounts Receivable	[1]	6		8
Payments to Acquire Other Receivables, Net		60		51	[3]
PEPCO Holdings Inc [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables				100
Allowance for Doubtful Accounts Receivable	[1]			6
Payments to Acquire Other Receivables, Net				94
PEPCO Holdings Inc [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		117
Allowance for Doubtful Accounts Receivable	[1]	6
Payments to Acquire Other Receivables, Net		$ 111
Potomac Electric Power Company [Member] | Maryland Service Territory [Member] | Minimum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		0.00%
Potomac Electric Power Company [Member] | Maryland Service Territory [Member] | Maximum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		2.00%
Potomac Electric Power Company [Member] | District of Columbia Service Territory [Member] | Minimum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		0.00%
Potomac Electric Power Company [Member] | District of Columbia Service Territory [Member] | Maximum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		6.00%
Potomac Electric Power Company [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables				70
Allowance for Doubtful Accounts Receivable	[4]			4
Payments to Acquire Other Receivables, Net				66
Potomac Electric Power Company [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 79
Allowance for Doubtful Accounts Receivable	[4]	4
Payments to Acquire Other Receivables, Net		$ 75
Delmarva Power and Light Company [Member] | Maryland Service Territory [Member] | Minimum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		0.00%
Delmarva Power and Light Company [Member] | Maryland Service Territory [Member] | Maximum [Member]
Purchase Of Receivables [Line Items]
Weighted Average Discount Rate, Percent		1.00%
Delmarva Power and Light Company [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables				11
Allowance for Doubtful Accounts Receivable	[1]			0
Payments to Acquire Other Receivables, Net				11
Delmarva Power and Light Company [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 12
Allowance for Doubtful Accounts Receivable	[1]	0
Payments to Acquire Other Receivables, Net		12
Atlantic City Electric Company [Member] | Predecessor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables				19
Allowance for Doubtful Accounts Receivable	[1]			2
Payments to Acquire Other Receivables, Net				$ 17
Atlantic City Electric Company [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		26
Allowance for Doubtful Accounts Receivable	[1]	2
Payments to Acquire Other Receivables, Net		$ 24

[1] For ComEd, BGE, Pepco and DPL, reflects the incremental allowance for uncollectible accounts recorded, which is in addition to the purchase discount. For ComEd, the incremental uncollectible accounts expense is recovered through its Purchase of Receivables with Consolidated Billing tariff

[2] PECO’s natural gas POR program became effective on January 1, 2012 and included a 1% discount on purchased receivables in order to recover the implementation costs of the program. The implementation costs were fully recovered and the 1% discount was reset to 0%, effective July 2015

[3] As of September 30, 2016, BGE's regulatory asset of $25 million included $3 million of costs associated with transmission costs recoverable through its FERC approved formula rate, $19 million related to under-recovered electric energy costs, $3 million of abandonment costs to be recovered upon FERC approval, and $1 million related to under-recovered natural gas costs. As of December 31, 2015, BGE’s regulatory asset of $40 million included $12 million of costs associated with transmission costs recoverable through its FERC approved formula rate and $28 million related to under-recovered electric energy costs. As of December 31, 2015, BGE’s regulatory liability of $18 million related to $14 million of over-recovered transmission costs and $5 million of over-recovered natural gas costs, offset by $1 million of abandonment costs to be recovered upon FERC approval.

[4] Pepco's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 2% depending on customer class, and Pepco's electric POR program in the District of Columbia included a discount on purchased receivables ranging from 0% to 6% depending on customer class. DPL's electric POR program in Maryland included a discount on purchased receivables ranging from 0% to 1% depending on customer class.