Changes in Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions			3 Months Ended
		Mar. 31, 2016	Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2015	Mar. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues			$ 7,573			$ 8,830
Income before income taxes			310			1,101
Income taxes			(184)			(363)
Net income			123			738
Other Nonoperating Income (Expense)			114			80
Equity in (losses) earnings of unconsolidated affiliates			3
Interest Expense			277			335
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	[1]		31			(60)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[1]		(5)			(27)
Income taxes	[1]		2			10
Net income	[1]		(3)			(17)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense	[1]					2
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[1]		56			(71)
Income taxes	[1]		(22)
Net income	[1]		34			(43)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	[1],[2]		76
Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	[1],[3]					(90)
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues			4,739			5,840
Income before income taxes			411			711
Income taxes			(151)			(226)
Net income			257			485
Other Nonoperating Income (Expense)			93			94
Equity in (losses) earnings of unconsolidated affiliates			3
Interest Expense			87			90
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	[1]		(3)			(1)
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[1]		(5)			(1)
Income taxes	[1]		2
Net income	[1]		(3)			(1)
Exelon Generation Co L L C [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest Expense	[1]					2
PEPCO Holdings Inc [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income			1		$ (1)
PEPCO Holdings Inc [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues					0
Income before income taxes			0		0
Income taxes			0		0
Net income			0		0
PEPCO Holdings Inc [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Cash Flow Hedging [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues			0		0
PEPCO Holdings Inc [Member] | Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes			1		(2)
Income taxes			0		(1)
Net income			1		(1)
Prior service benefit reclassified to periodic benefit cost			0		0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax			1		$ (2)
PEPCO Holdings Inc [Member] | Predecessor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Nonoperating Income (Expense)				$ (4)		9
Equity in (losses) earnings of unconsolidated affiliates				$ 0
PEPCO Holdings Inc [Member] | Successor [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Nonoperating Income (Expense)		$ 2
Equity in (losses) earnings of unconsolidated affiliates		$ 0
Potomac Electric Power Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues			551			545
Income before income taxes			(133)			38
Income taxes			25			(12)
Net income			(108)			26
Other Nonoperating Income (Expense)			9			5
Equity in (losses) earnings of unconsolidated affiliates			0
Interest Expense			37			30
Delmarva Power and Light Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues			362			421
Income before income taxes			(81)			53
Income taxes			9			(21)
Net income			(72)			32
Other Nonoperating Income (Expense)			3			2
Equity in (losses) earnings of unconsolidated affiliates			0
Interest Expense			12			12
Atlantic City Electric Company [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues			291			334
Income before income taxes			(133)			14
Income taxes			33			(5)
Net income			(100)			9
Other Nonoperating Income (Expense)			4			1
Equity in (losses) earnings of unconsolidated affiliates			0
Interest Expense			$ 16			$ 16

[1] Amounts in parenthesis represent a decrease in net income.

[2] This AOCI component is included in the computation of net periodic pension and OPEB cost (see Note 13 — Retirement Benefits for additional details).

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