Segment Information - Reconciliation to Consolidated Financial Statements (Details) - USD ($) $ in Millions		3 Months Ended				6 Months Ended
		Jun. 30, 2015		Jun. 30, 2014		Jun. 30, 2015		Jun. 30, 2014		Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenues		$ 6,514	[1]	$ 6,024	[1]	$ 15,345	[2]	$ 13,261	[2]
Net income (loss)		633		557		1,372		651
Operating revenues from affiliates		1	[3]	0	[3]	3		0
Assets		92,213				92,213				$ 86,814
Operating Segments [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Revenues		4,232	[1]	3,789	[1]	10,074	[2],[4],[5]	8,179	[2],[4],[5]
Net income (loss)		390		372		875	[4],[5]	188	[4],[5]
Operating revenues from affiliates		152	[3]	201	[3]	362	[4],[5]	517	[4],[5]
Assets		45,125				45,125				45,348
Utility Taxes		24		21		51		45
Operating Segments [Member] | Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Revenues		1,148	[1]	1,128	[1]	2,333	[2]	2,262	[2]
Net income (loss)		99		111		189		209
Operating revenues from affiliates		1	[3]	0	[3]	2		1
Assets		25,961				25,961				25,392
Utility Taxes		55		56		117		119
Operating Segments [Member] | PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Revenues		661	[1]	656	[1]	1,646	[2]	1,649	[2]
Net income (loss)		70		84		209		173
Operating revenues from affiliates		0	[3]	0	[3]	1		1
Assets		10,126				10,126				9,943
Utility Taxes		32		30		67		65
Operating Segments [Member] | Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Revenues		628	[1]	653	[1]	1,664	[2]	1,707	[2]
Net income (loss)		47		19		157		106
Operating revenues from affiliates		1	[3]	2	[3]	8		18
Assets		8,017				8,017				8,078
Utility Taxes		21		19		44		43
Operating Segments [Member] | PECO Energy Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		49		49		112		137
Operating Segments [Member] | Baltimore Gas And Electric Company Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		97		87		235		207
Operating Segments [Member] | Commonwealth Edison Co Affiliate [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates		6		65		15		173
Other Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Revenues		340	[1],[6]	329	[1],[6]	657	[2],[7]	619	[2],[7]
Net income (loss)		28	[6]	(29)	[6]	(55)	[7]	(25)	[7]
Operating revenues from affiliates		340	[3],[6]	328	[3],[6]	656	[7]	618	[7]
Assets	[6]	14,526				14,526				9,794
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues		0
Intersegment Eliminations [Member] | Segment Elimination [Member]
Segment Reporting Information [Line Items]
Revenues		(495)	[1]	(531)	[1]	(1,029)	[2]	(1,155)	[2]
Net income (loss)		(1)		0		(3)		0
Operating revenues from affiliates		(493)	[3]	$ (531)	[3]	(1,026)		$ (1,155)
Assets		$ (11,542)				$ (11,542)				$ (11,741)

[1] (c)For the three months ended June 30, 2015 and 2014, utility taxes of $24 million and $21 million, respectively, are included in revenues and expenses for Generation. For the three months ended June 30, 2015 and 2014, utility taxes of $55 million and $56 million, respectively, are included in revenues and expenses for ComEd. For the three months ended June 30, 2015 and 2014, utility taxes of $32 million and $30 million, respectively, are included in revenues and expenses for PECO. For the three months ended June 30, 2015 and 2014, utility taxes of $21 million and $19 million, respectively, are included in revenues and expenses for BGE.

[2] (d)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] (d)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.

[4] (a)Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. Intersegment revenues for Generation for the six months ended June 30, 2015 include revenue from sales to PECO of $112 million and sales to BGE of $235 million in the Mid-Atlantic region, and sales to ComEd of $15 million in the Midwest. For the six months ended June 30, 2014, intersegment revenues for Generation include revenue from sales to PECO of $137 million and sales to BGE of $207 million in the Mid-Atlantic region, and sales to ComEd of $173 million in the Midwest region.

[5] (b)Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.

[6] (b)Other primarily includes Exelon’s corporate operations, shared service entities and other financing and investment activities.

[7] (c)For the six months ended June 30, 2015 and 2014, utility taxes of $51 million and $45 million, respectively, are included in revenues and expenses for Generation. For the six months ended June 30, 2015 and 2014, utility taxes of $117 million and $119 million, respectively, are included in revenues and expenses for ComEd. For the six months ended June 30, 2015 and 2014, utility taxes of $67 million and $65 million, respectively, are included in revenues and expenses for PECO. For the six months ended June 30, 2015 and 2014, utility taxes of $44 million and $43 million, respectively, are included in revenues and expenses for BGE.