Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended					9 Months Ended
	Sep. 30, 2016		Jun. 30, 2016	Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ (9,002)			$ (7,401)		$ (23,486)		$ (22,746)
Revenue from Related Parties	(1)			(2)
Net income (loss)	526			587		956		1,959
Derivative, Loss on Derivative			$ (3)
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,800)			(1,632)		(4,736)		(4,491)
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(451)			(520)		(1,272)		(1,746)
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(323)			(250)		(873)		(778)
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(295)			(316)		(665)		(687)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(238)			(376)		(686)		(880)
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(4,271)			(4,245)		(11,575)		(12,215)
Generation Reportable Segments Total [Member] | Scenario, Adjustment [Member]
Segment Reporting Information [Line Items]
Revenues				(54)				(144)
Revenue from Related Parties				(54)				(144)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(764)			(523)		(1,788)		(2,626)
Amortization of intangible assets related to commodity contracts	(21)			(3)		(10)		19
Derivative, Gain on Derivative	(187)							171
Derivative, Loss on Derivative				(7)		(366)
Generation All Other Segments [Member] | Scenario, Adjustment [Member]
Segment Reporting Information [Line Items]
Revenues				(54)				144
Revenue from Related Parties				(54)				(144)
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(5,035)			(4,768)		(13,363)		(14,841)
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,813)	[1]		(1,640)	[1]	(4,776)	[2],[3]	(4,560)	[2],[3]
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(455)	[1]		(520)	[1]	(1,278)	[3]	(1,752)	[3]
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(331)	[1]		(254)	[1]	(906)	[2],[3]	(783)	[2],[3]
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(289)	[1]		(317)	[1]	(659)	[3]	(691)	[3]
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(271)	[1],[4]		(416)	[1],[4]	(728)	[3],[5]	(940)	[3],[5]
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(4,322)	[1]		(4,299)	[1]	(11,677)	[3]	(12,360)	[3]
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(5,035)	[1]		(4,768)	[1]	(13,363)	[3]	(14,841)	[3]
Operating Segments [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Net income (loss)	271			332		556		1,208
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Net income (loss)	(125)			(36)		(340)		(96)
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(713)	[1],[6]		(469)	[1],[6]	(1,686)	[3],[7]	(2,481)	[3],[7]
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	885			555		(3)		(3)
Net income (loss)	(1)			(2)		(3)		(3)
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties						(1,166)		(1,003)
Intersegment Eliminations [Member] | Segment Elimination [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties						2,351		1,581
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	13			8		40	[2]	69	[2]
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	4			0		6		6
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	8			4		33	[2]	5	[2]
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(6)			1		(6)		4
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	33	[4]		40	[4]	42	[5]	60	[5]
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	51			54		102		145
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(51)	[6]		(54)	[6]	(102)	[7]	(145)	[7]
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	0			0		0		0
Intersegment Eliminations [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	$ (500)			$ (205)		$ (1,121)		$ (567)

[1] Three Months Ended September 30, 2016 Three Months Ended September 30, 2015 Revenuesfrom externalcustomers(a)IntersegmentrevenuesTotalRevenuesRevenuesfrom externalcustomers(a)(c)Intersegmentrevenues(c)TotalRevenues(c)Mid-Atlantic$1,813 $(13) $1,800 $1,640 $(8) $1,632Midwest1,163 1 1,164 1,152 (1) 1,151New England455 (4) 451 520 — 520New York331 (8) 323 254 (4) 250ERCOT289 6 295 317 (1) 316Other Power Regions271 (33) 238 416 (40) 376Total Revenues for Reportable Segments4,322 (51) 4,271 4,299 (54) 4,245Other(b)713 51 764 469 54 523Total Generation Consolidated Operating Revenues$5,035 $— $5,035 $4,768 $— $4,768

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk5ZDczZmJiZmVlMzQwYjliY2U1YWJiOTI2MjM3MWNhfFRleHRTZWxlY3Rpb246MTdGRTY4QTU5RDRENTQxRUI0NzhEODYyMUI4Q0UwRDQM}

[3] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk5ZDczZmJiZmVlMzQwYjliY2U1YWJiOTI2MjM3MWNhfFRleHRTZWxlY3Rpb246NDNBNkVDOEMwNDMyNUYwOEEwRjQ1MDc1RjM2NzgxOTMM}

[4] Three Months Ended September 30, 2016 Three Months Ended September 30, 2015 Revenuesfrom externalcustomers(a)IntersegmentrevenuesTotalRevenuesRevenuesfrom externalcustomers(a)(c)Intersegmentrevenues(c)TotalRevenues(c)Mid-Atlantic$1,813 $(13) $1,800 $1,640 $(8) $1,632Midwest1,163 1 1,164 1,152 (1) 1,151New England455 (4) 451 520 — 520New York331 (8) 323 254 (4) 250ERCOT289 6 295 317 (1) 316Other Power Regions271 (33) 238 416 (40) 376Total Revenues for Reportable Segments4,322 (51) 4,271 4,299 (54) 4,245Other(b)713 51 764 469 54 523Total Generation Consolidated Operating Revenues$5,035 $— $5,035 $4,768 $— $4,768

[5] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk5ZDczZmJiZmVlMzQwYjliY2U1YWJiOTI2MjM3MWNhfFRleHRTZWxlY3Rpb246NUY3NkI2RTJCMDAyNTZBQUJFNUZBOTU5MTExODhGMDgM}

[6] Three Months Ended September 30, 2016 Three Months Ended September 30, 2015 Revenuesfrom externalcustomers(a)IntersegmentrevenuesTotalRevenuesRevenuesfrom externalcustomers(a)(c)Intersegmentrevenues(c)TotalRevenues(c)Mid-Atlantic$1,813 $(13) $1,800 $1,640 $(8) $1,632Midwest1,163 1 1,164 1,152 (1) 1,151New England455 (4) 451 520 — 520New York331 (8) 323 254 (4) 250ERCOT289 6 295 317 (1) 316Other Power Regions271 (33) 238 416 (40) 376Total Revenues for Reportable Segments4,322 (51) 4,271 4,299 (54) 4,245Other(b)713 51 764 469 54 523Total Generation Consolidated Operating Revenues$5,035 $— $5,035 $4,768 $— $4,768

[7] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOjk5ZDczZmJiZmVlMzQwYjliY2U1YWJiOTI2MjM3MWNhfFRleHRTZWxlY3Rpb246QjRCNEYyM0QzNjhCNTEwRTlDNjBCQ0NFMEYxMzZERTAM}