Changes in Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		$ 6,514	[1]	$ 6,024	[1]	$ 15,345	[2]	$ 13,261	[2]
Income before income taxes		962		834		2,064		875
Income taxes		(327)		(277)		(690)		(224)
Net income		633		557		1,372		651
Prior service benefit reclassified to periodic benefit cost		8		5		15		5
Other Nonoperating Income (Expense)		(17)		230		64		330
Equity in losses of unconsolidated affiliates		0		0		(2)		(20)
Interest Expense		145		228		480		445
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	[3]	(46)		123		(106)		112
Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						2
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swap [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						(26)
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	[3]	(2)		63		(29)		102
Income taxes	[3]	0		(25)		10		(40)
Net income	[3]	(2)		38		(19)		62
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				63				102
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		(2)				(5)
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	[3]	(71)		(49)		(142)		(107)
Income taxes		27	[3]	18		55	[3]	41
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	[3]	(44)				(87)
Net income	[3]			(31)				(66)
Prior service benefit reclassified to periodic benefit cost		19	[3],[4]	12		38	[3],[4]	10
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax		(90)	[3],[4]	(61)		(180)	[3],[4]	(117)
Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[3]			193				193
Income taxes				(77)				(77)
Net income	[3]			116				116
Other Nonoperating Income (Expense)				193				193
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues		4,232		3,789		10,074		8,179
Income before income taxes		573		571		1,285		187
Income taxes		(181)		(199)		(407)		1
Net income		390		372		875		188
Other Nonoperating Income (Expense)		(31)		216		62		300
Equity in losses of unconsolidated affiliates				(1)		(3)		(20)
Interest Expense		90		74		180		147
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	[3]	(2)		154		(3)		178
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						2
Exelon Generation Co L L C [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swap [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues						0
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	[3]	(2)		63		(3)		102
Income taxes	[3]	0		(25)		0		(40)
Net income	[3]	(2)		38		(3)		62
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] | Energy Related Derivative [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Revenues				63				102
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]
Revenues		(2)				(5)
Exelon Generation Co L L C [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		0	[3]	0		0	[3]	0
Income taxes		0	[3]	0		0	[3]	0
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest	[3]	0				0
Net income				0				0
Prior service benefit reclassified to periodic benefit cost		0	[3],[4]	0		0	[3],[4]	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax		$ 0	[3],[4]	0		$ 0	[3],[4]	0
Exelon Generation Co L L C [Member] | Equity Method Investments | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	[3]			193				193
Income taxes				(77)				(77)
Net income	[3]			116				116
Other Nonoperating Income (Expense)				$ 193				$ 193

[1] (c)For the three months ended June 30, 2015 and 2014, utility taxes of $24 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014, utility taxes of $55 million and $56 million, respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014, utility taxes of $32 million and $30 million, respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014, utility taxes of $21 million and $19 million, respectively, are included in revenues and expenses for BGE.

[2] (d)Intersegment revenues exclude sales to unconsolidated affiliates. The intersegment profit associated with Generation’s sale of certain products and services by and between Exelon’s segments is not eliminated in consolidation due to the recognition of intersegment profit in accordance with regulatory accounting guidance. For Exelon, these amounts are included in Operating revenues in the Consolidated Statements of Operations and Comprehensive Income.

[3] All amounts are net of tax. Amounts in parentheses represent a decrease in net income.

[4] This accumulated other comprehensive income component is included in the computation of net periodic pension and OPEB cost (see Note 14— Retirement Benefits for additional details).