Segment Information - Generation Total Revenues (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017		Jun. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ (7,623)		$ (6,910)		$ (16,381)		$ (14,485)
Operating revenues from affiliates	0	[1]	1	[1]	0	[2]	2	[2]
Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,365)		(1,416)		(2,790)		(2,936)
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	(1,050)		(1,083)		(2,102)		(2,179)
Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(433)		(351)		(980)		(821)
Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(347)		(346)		(654)		(549)
Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(247)		(207)		(438)		(370)
Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(259)		(223)		(443)		(447)
Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(3,701)		(3,626)		(7,407)		(7,302)
Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(473)	[3]	(37)	[3]	(1,654)	[4]	(1,027)	[4]
Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(4,174)		(3,589)		(9,061)		(8,329)
Operating Segments [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Revenues	(1,356)	[5]	(1,432)	[5]	(2,785)	[6]	(2,964)	[6]
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	(1,058)	[5]	(1,076)	[5]	(2,107)	[6]	(2,166)	[6]
Operating Segments [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Revenues	(438)	[5]	(352)	[5]	(987)	[6]	(823)	[6]
Operating Segments [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Revenues	(352)	[5]	(356)	[5]	(662)	[6]	(573)	[6]
Operating Segments [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Revenues	(247)	[5]	(207)	[5]	(439)	[6]	(370)	[6]
Operating Segments [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Revenues	(268)	[5]	(232)	[5]	(457)	[6]	(456)	[6]
Operating Segments [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Revenues	(3,719)	[5]	(3,655)	[5]	(7,437)	[6]	(7,352)	[6]
Operating Segments [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Amortization of intangible assets related to commodity contracts	(15)		(9)		(17)		11
Unrealized Gain (Loss) on Securities	(143)		(615)		(98)		(553)
Operating Segments [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Revenues	(4,174)	[5]	(3,589)	[5]	(9,061)	[6]	(8,329)	[6]
Corporate, Non-Segment [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Revenues	(455)	[3],[5]	66	[3],[5]	(1,624)	[4],[6]	(977)	[4],[6]
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(734)	[1]	(771)	[1]	(1,503)	[2]	(1,466)	[2]
Intersegment Eliminations [Member] | Generation Mid Atlantic [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	9		(16)		5		(28)
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(8)		7		(5)		13
Intersegment Eliminations [Member] | Generation New England [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(5)		(1)		(7)		(2)
Intersegment Eliminations [Member] | Generation New York [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(5)		(10)		(8)		(24)
Intersegment Eliminations [Member] | Generation ERCOT [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	0		0		(1)		0
Intersegment Eliminations [Member] | Generation Other Regions [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(9)		(9)		(14)		(9)
Intersegment Eliminations [Member] | Generation Reportable Segments Total [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	(18)		(29)		(30)		(50)
Intersegment Eliminations [Member] | Generation All Other Segments [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	18	[3]	29	[3]	30	[4]	50	[4]
Intersegment Eliminations [Member] | Generation Total Consolidated Group [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	$ 0		$ 0		$ 0		$ 0

[1] 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.

[2] 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] Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $15 million and $9 million decrease to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the three months ended June 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $143 million and $615 million for the three months ended June 30, 2017 and 2016, respectively, and elimination of intersegment revenues.

[4] Other represents activities not allocated to a region. See text above for a description of included activities. Includes a $17 million decrease to revenues and an $11 million increase to revenues for the amortization of intangible assets and liabilities related to commodity contracts recorded at fair value for the six months ended June 30, 2017 and 2016, respectively, unrealized mark-to-market losses of $98 million and $553 million for the six months ended June 30, 2017 and 2016, respectively, and elimination of intersegment revenues.

[5] Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants.

[6] Includes all wholesale and retail electric sales to third parties and affiliated sales to the Utility Registrants.