Quarterly Data (Unaudited) - Quarterly Operating Results (Details) - USD ($) $ in Millions	2 Months Ended	3 Months Ended												12 Months Ended
	Dec. 31, 2014	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Selected Quarterly Financial Information [Line Items]
Operating Revenues		$ 6,702		$ 7,401		$ 6,514		$ 8,830	$ 7,255	$ 6,912	$ 6,024	$ 7,237		$ 29,447	$ 27,429	$ 24,888
Operating Income		707
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		309	[1]	629		638		693	18	993	522	90	[2]	2,250	1,820	1,729
Reclassifications to Operating Income (Loss)										2	7	(1)
Unrecognized Tax Benefits, Interest on Income Taxes Accrued												265
Exelon Generation Co L L C [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues	$ 386	4,294		4,768		4,232		5,840	4,802	4,412	3,789	4,390		19,135	17,393	15,630
Operating Income		230							(105)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (42)	154		377		398		443	(91)	771	340	(185)		1,340	1,019	1,060
Reclassifications to Operating Income (Loss)										1	7	(1)
Commonwealth Edison Co [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues		1,196		1,376		1,148		1,185	1,079	1,222	1,128	1,134		4,905	4,564	4,464
Operating Income		217		327	[3]	243	[3]	230	196	287	258	238
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		87		149		99		90	73	126	111	98		426	408	249
Reclassifications to Operating Income (Loss)				1
Unrecognized Tax Benefits, Interest on Income Taxes Accrued												172
PECO Energy Co [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues		645		740		661		985	750	693	656	993		3,032	3,094	3,100
Operating Income		128		154		124		223	156	133	134	149
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		79		90		70		139	98	81	84	89		378	352	395
Baltimore Gas and Electric Company [Member]
Selected Quarterly Financial Information [Line Items]
Operating Revenues		746		725		628		1,036	761	697	653	1,054		3,135	3,165	3,065
Operating Income		144		110		99		204	113	102	55	169
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		$ 74		$ 51		$ 44		$ 106	$ 52	$ 46	$ 16	$ 85		$ 288	$ 211	$ 210

[1] Includes charges to earnings related to the impairments of certain generating assets which were held for sale and certain Upstream exploration assets. See Note 8—Impairment of Long-Lived Assets of the Combined Notes to Consolidated Financial Statements for additional information.

[2] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmJiZTkxZGVlYTU0NDQzYzU5MmI5ODA2YTIzODFjMGRkfFRleHRTZWxlY3Rpb246NEExNTZFREE4NkYwMUZCQUZDQTExMjI1RThCRDM3QzcM}

[3] In both the second and third quarter of 2014, ComEd reclassified $1 million to Operating income for presentation purposes in ComEd's Consolidated Statements of Operations and Comprehensive Income. The reclassifications did not affect ComEd's Net (Loss) Income.