Consolidated Balance Sheets (Unaudited) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Assets, Current [Abstract]
Cash and cash equivalents	$ 1,825		$ 1,878
Restricted cash and cash equivalents	297		271
Accounts receivable, net
Customer	3,702		3,482
Other	1,077		1,227
Mark-to-market derivative assets	1,117		1,279
Unamortized energy contract assets	209		254
Inventories, net
Fossil fuel and emission allowances	266		579
Materials and supplies	1,035		1,024
Deferred income taxes	231		244
Regulatory assets	804		847
Disposal Group, Including Discontinued Operation, Assets, Current	1		147
Other	793		865
Total current assets	11,357		12,097
Property, plant and equipment, net	53,001		52,087
Deferred debits and other assets
Regulatory assets	6,068		6,076
Nuclear decommissioning trust funds	10,712		10,537
Investments	568		544
Goodwill	2,672		2,672
Mark-to-market derivative assets	913		773
Unamortized energy contracts assets	558		549
Pledged assets for Zion Station decommissioning	308		319
Other	1,234		1,160
Total deferred debits and other assets	23,033		22,630
Total assets	87,391		86,814
Liabilities, Current [Abstract]
Short-term borrowings	309		460
Long-term debt due within one year	1,260		1,802
Accounts payable	2,839		3,048
Accrued expenses	1,230		1,539
Regulatory liabilities	421		310
Mark-to-market derivative liabilities (current liabilities)	117		234
Unamortized energy contract liabilities	172		238
Other	1,018		1,123
Due to Affiliate, Current	8		8
Total current liabilities	7,374		8,762
Long-term debt	20,519		19,362
Long-term debt to financing trusts	648		648
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits	13,218		13,019
Asset retirement obligations	7,446		7,295
Pension obligations	3,154		3,366
Non-pension postretirement benefit obligations	1,825		1,742
Spent nuclear fuel obligation	1,021		1,021
Regulatory liabilities	4,566		4,550
Mark-to-market derivative liabilities (noncurrent liabilities)	491		403
Unamortized energy contract liabilities	189		211
Payable for Zion Station decommissioning	136		155
Other	2,166		2,147
Total deferred credits and other liabilities	34,212		33,909
Total liabilities	62,753	[1]	62,681	[1]
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock	16,731		16,709
Treasury stock, at cost (35 shares at both March 31, 2015 and December 31, 2014)	(2,327)		(2,327)
Retained earnings	11,334		10,910
Accumulated other comprehensive loss, net	(2,673)	[2]	(2,684)	[2]
Total shareholders’ equity	23,065		22,608
BGE preference stock not subject to mandatory redemption	193		193
Noncontrolling interest	1,380		1,332
Total equity	24,638		24,133
Total liabilities and shareholders’ equity	87,391		86,814
Member’s equity
Accumulated other comprehensive loss, net	(2,673)	[2]	(2,684)	[2]
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets	8,182		8,160
Deferred credits and other liabilities
Total liabilities	2,702		2,723
Exelon Generation Co L L C [Member]
Assets, Current [Abstract]
Cash and cash equivalents	532		780
Restricted cash and cash equivalents	179		158
Accounts receivable, net
Customer	2,320		2,295
Other	378		318
Mark-to-market derivative assets	1,116		1,276
Unamortized energy contract assets	209		254
Receivables from affiliates	115		113
Inventories, net
Fossil fuel and emission allowances	232		465
Materials and supplies	841		847
Deferred income taxes	266		327
Disposal Group, Including Discontinued Operation, Assets, Current	1		147
Other	530		658
Total current assets	6,719		7,638
Property, plant and equipment, net	23,414		22,945
Deferred debits and other assets
Nuclear decommissioning trust funds	10,712		10,537
Investments	122		104
Goodwill	47		47
Mark-to-market derivative assets	911		771
Unamortized energy contracts assets	558		549
Deferred Tax Assets, Net, Noncurrent	3		3
Pledged assets for Zion Station decommissioning	308		319
Other	776		731
Prepaid pension asset	1,748		1,704
Total deferred debits and other assets	15,185		14,765
Total assets	45,318	[3]	45,348	[3]
Liabilities, Current [Abstract]
Short-term borrowings	25		36
Long-term debt due within one year	75		58
Accounts payable	1,634		1,759
Accrued expenses	694		886
Mark-to-market derivative liabilities (current liabilities)	97		214
Unamortized energy contract liabilities	172		238
Other	532		605
Payables to affiliates	110		107
Related Party Transaction, Due from (to) Related Party	936
Due to Affiliate, Current	0		556
Total current liabilities	4,275		4,459
Long-term debt	7,477		6,709
Long-term debt to affiliate	940		943
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits	6,091		6,034
Asset retirement obligations	7,296		7,146
Non-pension postretirement benefit obligations	919		915
Spent nuclear fuel obligation	1,021		1,021
Mark-to-market derivative liabilities (noncurrent liabilities)	121		105
Unamortized energy contract liabilities	189		211
Payable for Zion Station decommissioning	136		155
Other	764		719
Payables to affiliates	2,921		2,880
Total deferred credits and other liabilities	19,458		19,186
Total liabilities	32,150	[3]	31,297	[3]
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Accumulated other comprehensive loss, net	(53)	[2]	(36)	[2]
Noncontrolling interest	1,380		1,333
Member’s equity
Membership interest	8,951		8,951
Undistributed earnings	2,890		3,803
Accumulated other comprehensive loss, net	(53)	[2]	(36)	[2]
Total member's equity	11,788		12,718
Total equity	13,168		14,051
Total liabilities and equity	45,318		45,348
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets	8,118		8,119
Deferred credits and other liabilities
Total liabilities	2,486		2,507
Commonwealth Edison Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents	108		66
Restricted cash and cash equivalents	4		4
Accounts receivable, net
Customer	503		477
Other	512		648
Receivables from affiliates	17		14
Inventories, net
Regulatory assets	317		349
Other	41		40
Inventories, net	135		125
Total current assets	1,637		1,723
Property, plant and equipment, net	16,099		15,793
Deferred debits and other assets
Regulatory assets	866		852
Investments	6		6
Goodwill	2,625		2,625
Other	276		271
Receivable from affiliate	2,603		2,571
Prepaid pension asset	1,619		1,551
Total deferred debits and other assets	7,995		7,876
Total assets	25,731		25,392
Liabilities, Current [Abstract]
Short-term borrowings	283		304
Long-term debt due within one year	260		260
Accounts payable	534		598
Accrued expenses	223		331
Deferred income taxes	44		63
Regulatory liabilities	131		125
Mark-to-market derivative liabilities (current liabilities)	20		20
Other	69		73
Customer deposits	128		128
Due to Affiliate, Current	84		84
Total current liabilities	1,776		1,986
Long-term debt	6,099		5,698
Long-term debt to financing trusts	206		206
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits	4,553		4,498
Asset retirement obligations	103		103
Non-pension postretirement benefit obligations	262		263
Regulatory liabilities	3,692		3,655
Mark-to-market derivative liabilities (noncurrent liabilities)	221		187
Other	881		889
Total deferred credits and other liabilities	9,712		9,595
Total liabilities	17,793		17,485
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock	1,588		1,588
Retained earnings	866		851
Other paid-in capital	5,484		5,468
Total shareholders’ equity	7,938		7,907
Total liabilities and shareholders’ equity	25,731		25,392
PECO Energy Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents	38		30
Restricted cash and cash equivalents	2		2
Accounts receivable, net
Customer	390		320
Other	123		141
Receivables from affiliates	3		3
Inventories, net
Fossil fuel and emission allowances	19		57
Materials and supplies	26		22
Deferred income taxes	70		69
Regulatory assets	41		29
Other	30		31
Prepaid utility taxes	107		10
Total current assets	849		714
Property, plant and equipment, net	6,867		6,801
Deferred debits and other assets
Regulatory assets	1,543		1,529
Investments	31		31
Other	32		34
Receivable from affiliate	500		490
Prepaid pension asset	347		344
Total deferred debits and other assets	2,453		2,428
Total assets	10,169		9,943
Liabilities, Current [Abstract]
Accounts payable	334		337
Accrued expenses	109		91
Regulatory liabilities	119		90
Other	31		31
Payables to affiliates	65		0
Customer deposits	53		52
Due to Affiliate, Current	57		52
Total current liabilities	768		653
Long-term debt	2,246		2,246
Long-term debt to financing trusts	184		184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits	2,708		2,671
Asset retirement obligations	29		29
Non-pension postretirement benefit obligations	287		287
Regulatory liabilities	662		657
Other	95		95
Total deferred credits and other liabilities	3,781		3,739
Total liabilities	6,979		6,822
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock	2,439		2,439
Retained earnings	750		681
Accumulated other comprehensive loss, net	1	[2]	1	[2]
Total shareholders’ equity	3,190		3,121
Total liabilities and shareholders’ equity	10,169		9,943
Member’s equity
Accumulated other comprehensive loss, net	1	[2]	1	[2]
Baltimore Gas and Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents	41		64
Restricted cash and cash equivalents	48		50
Accounts receivable, net
Customer	489		390
Other	99		82
Inventories, net
Fossil fuel and emission allowances	16		57
Materials and supplies	33		30
Deferred income taxes	15		6
Regulatory assets	187		214
Other	4		5
Prepaid utility taxes	30		59
Total current assets	962		957
Property, plant and equipment, net	6,280		6,204
Deferred debits and other assets
Regulatory assets	491		510
Investments	12		12
Other	28		25
Prepaid pension asset	357		370
Total deferred debits and other assets	888		917
Total assets	8,130		8,078
Liabilities, Current [Abstract]
Short-term borrowings	0		120
Long-term debt due within one year	75		75
Accounts payable	222		215
Accrued expenses	155		131
Deferred income taxes	36		52
Regulatory liabilities	124		44
Other	27		51
Customer deposits	95		92
Due to Affiliate, Current	46		66
Total current liabilities	780		846
Long-term debt	1,867		1,867
Long-term debt to financing trusts	258		258
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits	1,924		1,865
Asset retirement obligations	18		17
Non-pension postretirement benefit obligations	211		212
Regulatory liabilities	187		200
Other	62		60
Total deferred credits and other liabilities	2,402		2,354
Total liabilities	5,307	[4]	5,325	[4]
Stockholders' Equity Attributable to Parent [Abstract]
Common stock	1,360		1,360
Retained earnings	1,273		1,203
Total shareholders’ equity	2,633		2,563
BGE preference stock not subject to mandatory redemption	190		190
Total equity	2,823		2,753
Total liabilities and shareholders' equity	8,130		8,078
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets	49		24
Deferred credits and other liabilities
Total liabilities	$ 200		$ 197

[1] Exelon’s consolidated assets include $8,182 million and $8,160 million at March 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 $2,702 million and $2,723 million at March 31, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 - Variable Interest Entities.

[2] All amounts are net of tax. Amounts in parentheses represent a decrease in accumulated other comprehensive income.

[3] Generation’s consolidated assets include $8,118 million and $8,119 million at March 31, 2015 and December 31, 2014, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $2,486 million and $2,507 million at March 31, 2015 and December 31, 2014, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 3 - Variable Interest Entities.

[4] BGE’s consolidated assets include $49 million and $24 million at March 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 $200 million and $197 million at March 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 3 — Variable Interest Entities.