Regulatory Matters Regulatory Matters - Purchase of Receivables Programs (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2017		Dec. 31, 2016
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 305		$ 313
Allowance for Doubtful Accounts Receivable		(36)	[1]	(37)
Payments to Acquire Other Receivables, Net		269		276
Commonwealth Edison Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		85		87
Allowance for Doubtful Accounts Receivable		(14)	[1]	(14)
Payments to Acquire Other Receivables, Net		71		73
PECO Energy Co [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		72		72
Allowance for Doubtful Accounts Receivable	[2]	(7)		(6)
Payments to Acquire Other Receivables, Net		65		66
Baltimore Gas and Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		59		59
Allowance for Doubtful Accounts Receivable	[1]	(4)		(4)
Payments to Acquire Other Receivables, Net		55		55	[3]
PEPCO Holdings Inc [Member] | Successor [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		89		95
Allowance for Doubtful Accounts Receivable	[1]	(11)		(13)
Payments to Acquire Other Receivables, Net		78		82
Potomac Electric Power Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		58		63
Allowance for Doubtful Accounts Receivable	[4]	(6)		(7)
Payments to Acquire Other Receivables, Net		$ 52		56
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%
Delmarva Power and Light Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 10		10
Allowance for Doubtful Accounts Receivable	[1]	(2)		(2)
Payments to Acquire Other Receivables, Net		$ 8		8
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%
Atlantic City Electric Company [Member]
Purchase Of Receivables [Line Items]
Payments to Acquire Other Receivables		$ 21		22
Allowance for Doubtful Accounts Receivable	[1]	(3)		(4)
Payments to Acquire Other Receivables, Net		$ 18		$ 18

[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] .

[3] As of March 31, 2017, PECO's regulatory liability of $66 million included $41 million related to over-recovered costs under the DSP program, $13 million related to the over-recovered natural gas costs under the PGC, $10 million related to over-recovered non-bypassable transmission service charges and $2 million related to over-recovered electric transmission costs. As of December 31, 2016, PECO's regulatory liability of $56 million included $34 million related to over-recovered costs under the DSP program, $10 million related to over-recovered non-bypassable transmission service charges, $8 million related to the over-recovered natural gas costs under the PGC and $4 million related to the over-recovered electric transmission costs.

[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.