Segment Information - Analysis and Reconciliation to Consolidated Financial Statements (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
Segment Reporting Information [Line Items]
Revenues			$ 6,702		$ 7,401	$ 6,514	$ 8,830	$ 7,255	$ 6,912	$ 6,024	$ 7,237		$ 29,447		$ 27,429		$ 24,888
Competitive Energy Revenue													15,200		13,773		12,496
Other Alternative Energy Sales Revenue															154
Electric Revenue													9,876		9,467		9,365
Gas Domestic Regulated Revenue													1,176		1,325		1,246
Other Operating Income													757				46
Revenue from Purchased Oil and Gas													2,433		2,704		1,721
Operating revenues from affiliates													9		23		70
Depreciation and amortization													2,450		2,314		2,153
Operating Expenses	[1]												25,056		25,039		21,242
Equity in earnings (losses) of unconsolidated affiliates													(7)		(20)		10
Interest expense, net													1,033		1,065		1,356
Income (loss) from continuing operations before income taxes													3,330		2,486		2,773
Income taxes													1,073		666		1,044
Net income			309	[2]	629	638	693	18	993	522	90	[3]	2,250		1,820		1,729
Assets	[4]	$ 86,416	95,384					86,416					95,384		86,416
Utility taxes	[5]												474		456		449
Payments to Acquire Property, Plant, and Equipment													7,624		6,077		5,395
Sales Revenue, Services, Other													5		6		14
PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[6]												1		1		10
Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues													4,710		4,475		4,270
Operating Segments [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	[7]												15,944		14,533		13,862
Electric Revenue	[7]												0		0		0
Gas Domestic Regulated Revenue	[7]												0		0		0
Other Operating Income	[7]												758		155		47
Revenue from Purchased Oil and Gas	[7]												2,433		2,705		1,721
Depreciation and amortization	[7]												1,054		967		856
Operating Expenses	[1],[7]												16,872		16,923		13,976
Equity in earnings (losses) of unconsolidated affiliates	[7]												(8)		(20)		10
Interest expense, net	[7]												365		356		357
Income (loss) from continuing operations before income taxes	[7]												1,850		1,226		1,675
Income taxes	[7]												502		207		615
Net income	[7]												1,340		1,019		1,060
Assets	[7]	44,951	46,529					44,951					46,529		44,951
Payments to Acquire Property, Plant, and Equipment	[7]												3,841		3,012		2,752
Sales Revenue, Services, Other	[7]												0		0		0
Operating Segments [Member] | Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue													0		0		0
Electric Revenue													4,905		4,564		4,464
Gas Domestic Regulated Revenue													0		0		0
Other Operating Income													0		0		0
Revenue from Purchased Oil and Gas													0		0		0
Depreciation and amortization													707		687		669
Operating Expenses	[1]												3,889		3,586		3,510
Equity in earnings (losses) of unconsolidated affiliates													0		0		0
Interest expense, net													332		321		579
Income (loss) from continuing operations before income taxes													706		676		401
Income taxes													280		268		152
Net income													426		408		249
Assets		25,358	26,532					25,358					26,532		25,358
Payments to Acquire Property, Plant, and Equipment													2,398		1,689		1,433
Sales Revenue, Services, Other													0		0		0
Operating Segments [Member] | PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue													0		0		0
Electric Revenue													2,486		2,448		2,500
Gas Domestic Regulated Revenue													546		646		600
Other Operating Income													0		0		0
Revenue from Purchased Oil and Gas													0		0		0
Depreciation and amortization													260		236		228
Operating Expenses	[1]												2,404		2,522		2,434
Equity in earnings (losses) of unconsolidated affiliates													0		0		0
Interest expense, net													114		113		115
Income (loss) from continuing operations before income taxes													521		466		557
Income taxes													143		114		162
Net income													378		352		395
Assets		9,860	10,367					9,860					10,367		9,860
Payments to Acquire Property, Plant, and Equipment													601		661		537
Sales Revenue, Services, Other													0		0		0
Operating Segments [Member] | Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	[8]												0		0		0
Electric Revenue	[8]												2,490		2,460		2,405
Gas Domestic Regulated Revenue	[8]												645		705		660
Other Operating Income	[8]												0		0		0
Revenue from Purchased Oil and Gas	[8]												0		0		0
Depreciation and amortization	[8]												366		371		348
Operating Expenses	[1],[8]												2,578		2,726		2,616
Equity in earnings (losses) of unconsolidated affiliates	[8]												0		0		0
Interest expense, net	[8]												99		106		122
Income (loss) from continuing operations before income taxes	[8]												477		351		344
Income taxes	[8]												189		140		134
Net income	[8]												288		211		210
Assets	[8]	8,056	8,295					8,056					8,295		8,056
Payments to Acquire Property, Plant, and Equipment	[8]												719		620		587
Sales Revenue, Services, Other	[8]												0		0		0
Operating Segments [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Revenues	[9]												4,712		4,488		4,298
Other Segments [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue	[10]												0		0		0
Electric Revenue	[10]												0		0		0
Gas Domestic Regulated Revenue	[10]												0		0		0
Other Operating Income	[10]												0		0		0
Revenue from Purchased Oil and Gas	[10]												0		0		0
Depreciation and amortization	[10]												63		53		52
Operating Expenses	[1],[10]												1,444		1,353		1,324
Equity in earnings (losses) of unconsolidated affiliates	[10]												1		0		0
Interest expense, net	[10]												123		169		183
Income (loss) from continuing operations before income taxes	[10]												(219)		(227)		(191)
Income taxes	[10]												(41)		(63)		(20)
Net income	[10]												(177)		(164)		(171)
Assets	[10]	9,711	15,389					9,711					15,389		9,711
Payments to Acquire Property, Plant, and Equipment	[10]												65		95		86
Sales Revenue, Services, Other	[10]												1,372		1,285		1,241
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Competitive Energy Revenue													(744)		(760)		(1,366)
Electric Revenue													(5)		(5)		(4)
Gas Domestic Regulated Revenue													(15)		(26)		(14)
Other Operating Income													(1)		(1)		(1)
Revenue from Purchased Oil and Gas													0		(1)		0
Operating revenues from affiliates	[11]												5		6		14
Depreciation and amortization													0		0		0
Operating Expenses	[1]												(2,131)		(2,071)		(2,618)
Equity in earnings (losses) of unconsolidated affiliates													0		0		0
Interest expense, net													0		0		0
Income (loss) from continuing operations before income taxes													(5)		(6)		(13)
Income taxes													0		0		1
Net income													(5)		(6)		(14)
Assets		(11,520)	(11,728)					(11,520)					(11,728)		(11,520)
Payments to Acquire Property, Plant, and Equipment													0		0		0
Sales Revenue, Services, Other													(1,367)		(1,279)		(1,227)
Intersegment Eliminations [Member] | Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates													745		762	[7],[11]	1,367	[7],[11]
Intersegment Eliminations [Member] | Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates													4		4	[11]	3	[11]
Intersegment Eliminations [Member] | PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates													2	[12]	2	[11]	1	[11]
Intersegment Eliminations [Member] | Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates													14	[13]	25	[8],[11]	13	[8],[11]
Intersegment Eliminations [Member] | Corporate and Other [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[10],[11]												1,367		1,280		1,237
Intersegment Eliminations [Member] | Generation Midwest [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates													(2)		(13)		(28)
Intersegment Eliminations [Member] | Segment Elimination [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[11]												(2,127)		(2,067)		(2,607)
Exelon Generation Co L L C [Member]
Segment Reporting Information [Line Items]
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 revenues from affiliates													749		779		1,423
Equity in earnings (losses) of unconsolidated affiliates													(8)
Income (loss) from continuing operations before income taxes													1,850		1,226		1,675
Income taxes													502		207		615
Net income		(42)	154		377	398	443	(91)	771	340	(185)		1,340		1,019		1,060
Assets	[14]	44,951	46,529					44,951					46,529		44,951
Utility taxes	[5]												105		89		79
Payments to Acquire Property, Plant, and Equipment													3,841		3,012		2,752
Exelon Generation Co L L C [Member] | PECO Energy Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[15]												224		198		405
Exelon Generation Co L L C [Member] | Baltimore Gas And Electric Company Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[16]												502		387		455
Exelon Generation Co L L C [Member] | Commonwealth Edison Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[17]												18		176		506
Exelon Generation Co L L C [Member] | Intersegment Eliminations [Member] | Commonwealth Edison Co Affiliate [Member]
Segment Reporting Information [Line Items]
Operating revenues from affiliates	[17]																7
Commonwealth Edison Co [Member]
Segment Reporting Information [Line Items]
Revenues			1,196		1,376	1,148	1,185	1,079	1,222	1,128	1,134		4,905		4,564		4,464
Operating revenues from affiliates													4		4		3
Income taxes													280		268		152
Net income			87		149	99	90	73	126	111	98		426		408		249
Assets		25,358	26,532					25,358					26,532		25,358
Utility taxes	[5]												236		238		241
Payments to Acquire Property, Plant, and Equipment													2,398		1,689		1,433
PECO Energy Co [Member]
Segment Reporting Information [Line Items]
Revenues			645		740	661	985	750	693	656	993		3,032		3,094		3,100
Electric Revenue													2,485		2,446		2,499
Gas Domestic Regulated Revenue													545		646		600
Operating revenues from affiliates													2		2		1
Income (loss) from continuing operations before income taxes													521		466		557
Income taxes													143		114		162
Net income			79		90	70	139	98	81	84	89		378		352		395
Assets		9,860	10,367					9,860					10,367		9,860
Utility taxes	[5]												133		128		129
Payments to Acquire Property, Plant, and Equipment													601		661		537
Baltimore Gas and Electric Company [Member]
Segment Reporting Information [Line Items]
Revenues			746		725	628	1,036	761	697	653	1,054		3,135		3,165		3,065
Electric Revenue													2,490		2,460		2,405
Gas Domestic Regulated Revenue													631		680		647
Operating revenues from affiliates													14		25		13
Income (loss) from continuing operations before income taxes													477		351		344
Income taxes													189		140		134
Net income			74		$ 51	$ 44	$ 106	52	$ 46	$ 16	$ 85		288		211		210
Assets	[18]	$ 8,056	$ 8,295					$ 8,056					8,295		8,056
Utility taxes	[5]												85		86		82
Payments to Acquire Property, Plant, and Equipment													$ 719		$ 620		$ 587

[1] 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.

[2] 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.

[3] {F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmJiZTkxZGVlYTU0NDQzYzU5MmI5ODA2YTIzODFjMGRkfFRleHRTZWxlY3Rpb246NEExNTZFREE4NkYwMUZCQUZDQTExMjI1RThCRDM3QzcM}

[4] Exelon’s consolidated assets include $8,268 million and $8,159 million at December 31, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,264 million and $2,728 million at December 31, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2–Variable Interest Entities.

[5] Generation’s utility tax represents gross receipts tax related to its retail operations and ComEd’s, PECO’s and BGE’s utility taxes represent municipal and state utility taxes and gross receipts taxes related to their operating revenues. The offsetting collection of utility taxes from customers is recorded in revenues on the Registrants’ Consolidated Statements of Operations and Comprehensive Income.

[6] The intersegment profit associated with the 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 Statement of Operations. See Note 3—Regulatory Matters for additional information.

[7] Generation includes the six power marketing reportable segments shown below: Mid-Atlantic, Midwest, New England, New York, ERCOT and Other Power Regions. For the year ended December 31, 2015, intersegment revenues for Generation include revenue from sales to PECO of $224 million and sales to BGE of $502 million in the Mid-Atlantic region, and sales to ComEd of $18 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2014, intersegment revenues for Generation include revenue from sales to PECO of $198 million and sales to BGE of $387 million in the Mid-Atlantic region, and sales to ComEd of $176 million in the Midwest region, which eliminate upon consolidation. For the year ended December 31, 2013, intersegment revenues for Generation include revenue from sales to PECO of $405 million and sales to BGE of $455 million in the Mid-Atlantic region, and sales to ComEd of $506 million in the Midwest region, net of $7 million related to the unrealized mark-to-market losses related to the ComEd swap, which eliminate upon consolidation.

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

[9] (a)On April 1, 2014, Generation assumed operational control of CENG's nuclear fleet. As a result, beginning on April 1, 2014, CENG's revenues are included on a fully consolidated basis.

[10] (c)For the years ended December 31, 2015, 2014 and 2013, utility taxes of $105 million, $89 million and $79 million, respectively, are included in revenues and expenses for Generation. For the years ended December 31, 2015, 2014 and 2013, utility taxes of $236 million, $238 million and $241 million, respectively, are included in revenues and expenses for ComEd. For the years ended December 31, 2015, 2014 and 2013, utility taxes of $133 million, $128 million and $129 million, respectively, are included in revenues and expenses for PECO. For the years ended December 31, 2015, 2014 and 2013, utility taxes of $85 million, $86 million and $82 million are included in revenues and expenses for BGE, respectively.

[11] 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.

[12] PECO provides energy to Generation for Generation’s own use.

[13] BGE provides energy to Generation for Generation’s own use.

[14] Generation’s consolidated assets include $8,235 million and $8,118 million at December 31, 2015 and 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,135 million and $2,512 million at December 31, 2015 and 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2–Variable Interest Entities.

[15] Generation provides electric supply to PECO under contracts executed through PECO’s competitive procurement process. In addition, Generation has five-year and ten-year agreements with PECO to sell non-solar and solar AECs, respectively. See Note 3—Regulatory Matters for additional information.

[16] Generation provides a portion of BGE’s energy requirements under its MDPSC-approved market-based SOS and gas commodity programs. See Note 3—Regulatory Matters for additional information.

[17] Generation has an ICC-approved RFP contract with ComEd to provide a portion of ComEd’s electricity supply requirements. Generation also sells RECs to ComEd. In addition, Generation had revenue from ComEd associated with the settled portion of the financial swap contract established as part of the Illinois Settlement. See Note 3—Regulatory Matters for additional information.

[18] BGE’s consolidated assets include $26 million and $24 million at December 31, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $122 million and $197 million at December 31, 2015 and December 31, 2014, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 2 - Variable Interest Entities.