Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2016		Jun. 30, 2015		Jun. 30, 2016		Jun. 30, 2015
Segment Reporting Information [Line Items]
Revenues	$ (6,910)		$ (6,514)		$ (14,485)		$ (15,345)
Revenue from Related Parties	(1)		(1)
Net income (loss)	306		633		430		1,372
Derivative, Loss on Derivative	(3)
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,416)		(1,346)		(2,936)		(2,859)
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(351)		(367)		(821)		(1,226)
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(346)		(218)		(549)		(528)
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(207)		(192)		(370)		(372)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(223)		(289)		(447)		(503)
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(3,626)		(3,618)		(7,302)		(7,970)
Generation Reportable Segments Total [Member] | Scenario, Adjustment [Member]
Segment Reporting Information [Line Items]
Revenues			(46)				(89)
Revenue from Related Parties			(46)				(89)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	37		(614)		(1,027)		(2,104)
Amortization of intangible assets related to commodity contracts	(9)		(17)		11		22
Derivative, Gain on Derivative			25				179
Derivative, Loss on Derivative	(615)				(553)
Generation All Other Segments [Member] | Scenario, Adjustment [Member]
Segment Reporting Information [Line Items]
Revenues			(46)				89
Revenue from Related Parties			(46)				(89)
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(3,589)		(4,232)		(8,329)		(10,074)
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,432)	[1]	(1,364)	[1]	(2,964)	[2],[3]	(2,920)	[2],[3]
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(352)	[1]	(367)	[1]	(823)	[3]	(1,232)	[3]
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(356)	[1]	(222)	[1]	(573)	[2],[3]	(529)	[2],[3]
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(207)	[1]	(194)	[1]	(370)	[3]	(375)	[3]
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(232)	[1],[4]	(310)	[1],[4]	(456)	[3],[5]	(522)	[3],[5]
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(3,655)	[1]	(3,663)	[1]	(7,352)	[3]	(8,060)	[3]
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(3,589)	[1]	(4,232)	[1]	(8,329)	[3]	(10,074)	[3]
Operating Segments [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Net income (loss)	28		390		285		875
Corporate, Non-Segment [Member]
Segment Reporting Information [Line Items]
Net income (loss)	(52)		28		(215)		(55)
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	66	[1],[6]	(569)	[1],[6]	(977)	[3],[7]	(2,014)	[3],[7]
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties	771		493		(2)		(1)
Net income (loss)	(1)		(1)		(2)		(3)
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties					(803)		(656)
Intersegment Eliminations [Member] | Segment Elimination [Member]
Segment Reporting Information [Line Items]
Revenue from Related Parties					1,466		1,026
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	16		18		28	[2]	61	[2]
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	1		0		2		6
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	10		4		24	[2]	1	[2]
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	0		2		0		3
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	9	[4]	21	[4]	9	[5]	19	[5]
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	29		45		50		90
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(29)	[6]	(45)	[6]	(50)	[7]	(90)	[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	$ (355)		$ (152)		$ (621)		$ (360)

[1] Three Months Ended June 30, 2016 Three Months Ended June 30, 2015 Revenuesfrom externalcustomers(a)IntersegmentrevenuesTotalRevenuesRevenuesfrom externalcustomers(a)(c)Intersegmentrevenues(c)TotalRevenues(c)Mid-Atlantic$1,432 $(16) $1,416 $1,364 $(18) $1,346Midwest1,076 7 1,083 1,206 — 1,206New England352 (1) 351 367 — 367New York356 (10) 346 222 (4) 218ERCOT207 — 207 194 (2) 192Other Power Regions232 (9) 223 310 (21) 289Total Revenues for Reportable Segments3,655 (29) 3,626 3,663 (45) 3,618Other(b)(66) 29 (37) 569 45 614Total Generation Consolidated Operating Revenues$3,589 $— $3,589 $4,232 $— $4,232

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmYxYjEyZjM4YzVjZDQ2YTM5N2E5NDQ4NWM2Nzk3Yjg1fFRleHRTZWxlY3Rpb246MjczNzA5QThFQTg3QjUwRUNENjZDNTVBNUYzRTFGRTQM}

[3] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmYxYjEyZjM4YzVjZDQ2YTM5N2E5NDQ4NWM2Nzk3Yjg1fFRleHRTZWxlY3Rpb246N0MwQjhEMjI5NzREODVBMzQxQjhDNTVBNUYzRTA3MDcM}

[4] Three Months Ended June 30, 2016 Three Months Ended June 30, 2015 Revenuesfrom externalcustomers(a)IntersegmentrevenuesTotalRevenuesRevenuesfrom externalcustomers(a)(c)Intersegmentrevenues(c)TotalRevenues(c)Mid-Atlantic$1,432 $(16) $1,416 $1,364 $(18) $1,346Midwest1,076 7 1,083 1,206 — 1,206New England352 (1) 351 367 — 367New York356 (10) 346 222 (4) 218ERCOT207 — 207 194 (2) 192Other Power Regions232 (9) 223 310 (21) 289Total Revenues for Reportable Segments3,655 (29) 3,626 3,663 (45) 3,618Other(b)(66) 29 (37) 569 45 614Total Generation Consolidated Operating Revenues$3,589 $— $3,589 $4,232 $— $4,232

[5] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmYxYjEyZjM4YzVjZDQ2YTM5N2E5NDQ4NWM2Nzk3Yjg1fFRleHRTZWxlY3Rpb246QzdEMzkzREYyOEI0NjREREJDNzVDNTVBNUYzRTI3QjIM}

[6] Three Months Ended June 30, 2016 Three Months Ended June 30, 2015 Revenuesfrom externalcustomers(a)IntersegmentrevenuesTotalRevenuesRevenuesfrom externalcustomers(a)(c)Intersegmentrevenues(c)TotalRevenues(c)Mid-Atlantic$1,432 $(16) $1,416 $1,364 $(18) $1,346Midwest1,076 7 1,083 1,206 — 1,206New England352 (1) 351 367 — 367New York356 (10) 346 222 (4) 218ERCOT207 — 207 194 (2) 192Other Power Regions232 (9) 223 310 (21) 289Total Revenues for Reportable Segments3,655 (29) 3,626 3,663 (45) 3,618Other(b)(66) 29 (37) 569 45 614Total Generation Consolidated Operating Revenues$3,589 $— $3,589 $4,232 $— $4,232

[7] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmYxYjEyZjM4YzVjZDQ2YTM5N2E5NDQ4NWM2Nzk3Yjg1fFRleHRTZWxlY3Rpb246RTI5RThGNUMzRjQyMjZCRTY4ODlDNTVBNUYzRUU2MEQM}