Changes in Accumulated Other Comprehensive Income - Reclassification out of Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	$ 6,912	[1]	$ 6,502	[1]	$ 20,173	[2]	$ 18,725	[2]
Income before income taxes	1,496		1,175		2,371		1,968
Income taxes	(422)		(439)		(646)		(733)
Net income	1,074		736		1,725		1,235
Prior service benefit reclassified to periodic benefit cost	8		0		11		0
Other Nonoperating Income (Expense)	354		155		702		311
Equity in earnings (loss) of unconsolidated affiliates	1		37		(20)		7
Interest Expense	247		228		691		1,091
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(7)	[3]	(8)	[3]	106	[3]	32	[3]
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	28	[3]	83	[3]	130	[3]	322	[3]
Income taxes	(12)	[3]	(35)	[3]	(52)	[3]	(128)	[3]
Net income	16	[3]	48	[3]	78	[3]	194	[3]
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]
Operating revenues	28	[3]	84	[3]	130	[3]	324	[3]
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)	[3]			(2)	[3]
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	(42)	[3]	(93)	[3]	(149)	[3]	(259)	[3]
Income taxes	16	[3]	37	[3]	58	[3]	102	[3]
Net income	(26)	[3]	(56)	[3]	(91)	[3]	(157)	[3]
Prior service benefit reclassified to periodic benefit cost	19	[3],[4]			29	[3],[4]	(1)	[3],[4]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax	(61)	[3],[4]	(92)	[3],[4]	(178)	[3],[4]	(257)	[3],[4]
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	5	[3]	0	[3]	198	[3]	(8)	[3]
Income taxes	(2)	[3]	0	[3]	(79)	[3]	3	[3]
Net income	3	[3]	0	[3]	119	[3]	(5)	[3]
Other Nonoperating Income (Expense)	5	[3]			5	[3]
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax			(1)	[3],[5]			(1)	[3],[5]
Equity in earnings (loss) of unconsolidated affiliates			0	[3]			(8)	[3]
Gain on consolidation of CENG					193	[3]
Exelon Generation Co L L C [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Operating revenues	4,412		4,255		12,591		11,858
Income before income taxes	1,140		773		1,327		1,231
Income taxes	(291)		(288)		(290)		(436)
Net income	849		485		1,037		795
Other Nonoperating Income (Expense)	342		134		661		229
Equity in earnings (loss) of unconsolidated affiliates	1		37		(20)		7
Interest Expense	77		69		224		210
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	19	[3]	50	[3]	197	[3]	323	[3]
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	28	[3]	83	[3]	130	[3]	543	[3]
Income taxes	(12)	[3]	(33)	[3]	(52)	[3]	(215)	[3]
Net income	16	[3]	50	[3]	78	[3]	328	[3]
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]
Operating revenues	28	[3]	84	[3]	130	[3]	543	[3]
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)	[3]			0	[3]
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	5	[3]	0	[3]	198	[3]	(8)	[3]
Income taxes	(2)	[3]	0	[3]	(79)	[3]	3	[3]
Net income	3	[3]	0	[3]	119	[3]	(5)	[3]
Other Nonoperating Income (Expense)	5	[3]			5	[3]
Equity in earnings (loss) of unconsolidated affiliates			0	[3]			(8)	[3]
Gain on consolidation of CENG					$ 193	[3]

[1] For the three months ended September 30, 2014 and 2013, utility taxes of $22 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended September 30, 2014 and 2013, utility taxes of $61 million and $65 million, respectively, are included in revenues and expenses for ComEd. For the three months ended September 30, 2014 and 2013, utility taxes of $34 million and $33 million, respectively, are included in revenues and expenses for PECO. For the three months ended September 30, 2014 and 2013, utility taxes of $21 million and $20 million, respectively, are included in revenues and expenses for BGE.

[2] For the nine months ended September 30, 2014 and 2013, utility taxes of $67 million and $60 million, respectively, are included in revenues and expenses for Generation. For the nine months ended September 30, 2014 and 2013, utility taxes of $180 million and $182 million, respectively, are included in revenues and expenses for ComEd. For the nine months ended September 30, 2014 and 2013, utility taxes of $99 million and $97 million, respectively, are included in revenues and expenses for PECO. For the nine months ended September 30, 2014 and 2013, utility taxes of $64 million and $62 million, respectively, are included in revenues and expenses for BGE.

[3] All amounts are net of tax. Amounts in parenthesis 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 13— Retirement Benefits for additional details).

[5] Amortization of deferred compensation unit is allocated to capital and operating and maintenance expense.