Income Taxes - Components of Income Tax Expense (Benefit) from Continuing Operations (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Income taxes	$ 1,073	$ 666	$ 1,044
Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Income taxes	502	207	615
Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Income taxes	280	268	152
PECO Energy Co [Member]
Income Taxes [Line Items]
Income taxes	143	114	162
Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Current	0	0	0
Income taxes	189	140	134
Internal Revenue Service (IRS) [Member]
Income Taxes [Line Items]
Current	407	121	744
Deferred	566	576	140
Investment Tax Credit	22	20	15
Internal Revenue Service (IRS) [Member] \| Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Current	546	360	250
Deferred	16	(35)	360
Investment Tax Credit	19	16	11
Internal Revenue Service (IRS) [Member] \| Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Current	(80)	(171)	160
Deferred	310	395	(27)
Investment Tax Credit	2	2	2
Internal Revenue Service (IRS) [Member] \| PECO Energy Co [Member]
Income Taxes [Line Items]
Current	64	28	126
Deferred	69	87	23
Investment Tax Credit	0	0	1
Internal Revenue Service (IRS) [Member] \| Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Current	25	24	9
Deferred	126	90	100
Investment Tax Credit	1	1	1
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Current	(86)	42	181
Deferred	208	(53)	(6)
State and Local Jurisdiction [Member] \| Exelon Generation Co L L C [Member]
Income Taxes [Line Items]
Current	(90)	35	50
Deferred	49	(137)	(34)
State and Local Jurisdiction [Member] \| Commonwealth Edison Co [Member]
Income Taxes [Line Items]
Current	7	7	50
Deferred	45	39	(29)
State and Local Jurisdiction [Member] \| PECO Energy Co [Member]
Income Taxes [Line Items]
Current	(10)	(2)	16
Deferred	20	1	(2)
State and Local Jurisdiction [Member] \| Baltimore Gas and Electric Company [Member]
Income Taxes [Line Items]
Deferred	$ 39	$ 27	$ 26

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Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
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-Publisher FASB
-Name Accounting Standards Codification
-Glossary Current Tax Expense (or Benefit)
-URI http://asc.fasb.org/extlink&oid=6509736

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
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Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section I
-Subsection 7

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Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Deferred Tax Expense (or Benefit)
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-Name Accounting Standards Codification
-Topic 235
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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; includes deferred investment tax credits.

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