Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Sep. 30, 2015	Dec. 31, 2014
Assets, Current [Abstract]
Cash and cash equivalents		$ 7,265	$ 1,878
Restricted cash and cash equivalents		341	271
Accounts receivable, net
Customer		3,215	3,482
Other		1,107	1,227
Mark-to-market derivative assets		1,116	1,279
Unamortized energy contract assets		135	254
Inventories, net
Fossil fuel and emission allowances		442	579
Materials and supplies		1,074	1,024
Deferred income taxes		211	244
Regulatory assets		779	847
Disposal Group, Including Discontinued Operation, Assets, Current		4	147
Other		1,178	865
Total current assets		16,867	12,097
Property, plant and equipment, net		55,814	52,087
Deferred debits and other assets
Regulatory assets		6,000	6,076
Nuclear decommissioning trust funds		10,103	10,537
Investments		620	544
Goodwill		2,672	2,672
Mark-to-market derivative assets		801	773
Unamortized energy contracts assets		513	549
Deferred Tax Assets, Net, Noncurrent		2	0
Pledged assets for Zion Station decommissioning		237	319
Other		1,499	1,160
Total deferred debits and other assets		22,447	22,630
Total assets		95,128	86,814
Liabilities, Current [Abstract]
Short-term borrowings		675	460
Long-term debt due within one year		897	1,802
Accounts payable		2,987	3,048
Accrued expenses		1,576	1,539
Regulatory liabilities		365	310
Mark-to-market derivative liabilities (current liabilities)		204	234
Unamortized energy contract liabilities		118	238
Other Liabilities, Current		1,017	1,123
Due to Affiliate, Current		8	8
Total current liabilities		7,847	8,762
Long-term debt		24,541	19,362
Long-term debt to financing trusts		648	648
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		13,480	13,019
Asset retirement obligations		8,405	7,295
Pension obligations		3,014	3,366
Non-pension postretirement benefit obligations		1,877	1,742
Spent nuclear fuel obligation		1,021	1,021
Regulatory liabilities		4,180	4,550
Mark-to-market derivative liabilities (noncurrent liabilities)		360	403
Unamortized energy contract liabilities		136	211
Payable for Zion Station decommissioning		99	155
Other		2,231	2,147
Total deferred credits and other liabilities		34,803	33,909
Total liabilities	[1]	$ 67,839	$ 62,681
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 18,647	$ 16,709
Treasury stock, at cost (35 shares at both September 30, 2015 and December 31, 2014)		(2,327)	(2,327)
Retained earnings		12,046	10,910
Accumulated other comprehensive loss, net	[2]	(2,596)	(2,684)
Total shareholders’ equity		25,770	22,608
BGE preference stock not subject to mandatory redemption		193	193
Noncontrolling interest		1,326	1,332
Total equity		27,289	24,133
Total liabilities and shareholders’ equity		95,128	86,814
Member’s equity
Accumulated other comprehensive loss, net	[2]	(2,596)	(2,684)
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,190	8,160
Deferred credits and other liabilities
Total liabilities		3,242	2,723
Exelon Generation Co L L C [Member]
Assets, Current [Abstract]
Cash and cash equivalents		545	780
Restricted cash and cash equivalents		242	158
Accounts receivable, net
Customer		2,056	2,295
Other		487	318
Mark-to-market derivative assets		1,116	1,276
Unamortized energy contract assets		135	254
Receivables from affiliates		84	113
Inventories, net
Fossil fuel and emission allowances		357	465
Materials and supplies		863	847
Deferred income taxes		201	327
Disposal Group, Including Discontinued Operation, Assets, Current		4	147
Other		960	658
Total current assets		7,050	7,638
Property, plant and equipment, net		24,982	22,945
Deferred debits and other assets
Nuclear decommissioning trust funds		10,103	10,537
Investments		197	104
Goodwill		47	47
Mark-to-market derivative assets		764	771
Unamortized energy contracts assets		513	549
Deferred Tax Assets, Net, Noncurrent		2	3
Pledged assets for Zion Station decommissioning		237	319
Other		881	731
Prepaid pension asset		1,703	1,704
Total deferred debits and other assets		14,447	14,765
Total assets	[3]	46,479	45,348
Liabilities, Current [Abstract]
Short-term borrowings		21	36
Long-term debt due within one year		97	58
Accounts payable		1,676	1,759
Accrued expenses		835	886
Mark-to-market derivative liabilities (current liabilities)		182	214
Unamortized energy contract liabilities		118	238
Other Liabilities, Current		546	605
Payables to affiliates		106	107
Related Party Transaction, Due from (to) Related Party		1,205	0
Due to Affiliate, Current		0	556
Total current liabilities		4,786	4,459
Long-term debt		7,964	6,709
Long-term debt to affiliate		935	943
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		6,030	6,034
Asset retirement obligations		8,254	7,146
Non-pension postretirement benefit obligations		926	915
Spent nuclear fuel obligation		1,021	1,021
Mark-to-market derivative liabilities (noncurrent liabilities)		139	105
Unamortized energy contract liabilities		136	211
Payable for Zion Station decommissioning		99	155
Other		727	719
Payables to affiliates		2,538	2,880
Total deferred credits and other liabilities		19,870	19,186
Total liabilities	[3]	33,555	31,297
Stockholders' Equity Attributable to Parent [Abstract]
Accumulated other comprehensive loss, net	[2]	(60)	(36)
Noncontrolling interest		1,325	1,333
Total equity		12,924	14,051
Member’s equity
Membership interest		9,006	8,951
Undistributed earnings		2,653	3,803
Accumulated other comprehensive loss, net	[2]	(60)	(36)
Total member's equity		11,599	12,718
Total equity		12,924	14,051
Total liabilities and equity		46,479	45,348
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,130	8,119
Deferred credits and other liabilities
Total liabilities		3,070	2,507
Commonwealth Edison Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		51	66
Restricted cash and cash equivalents		2	4
Accounts receivable, net
Customer		557	477
Other		334	648
Receivables from affiliates		14	14
Inventories, net
Regulatory assets		232	349
Other		84	40
Inventories, net		148	125
Total current assets		1,422	1,723
Property, plant and equipment, net		17,001	15,793
Deferred debits and other assets
Regulatory assets		913	852
Goodwill		2,625	2,625
Other		295	277
Receivable from affiliate		2,336	2,571
Prepaid pension asset		1,537	1,551
Total deferred debits and other assets		7,706	7,876
Total assets		26,129	25,392
Liabilities, Current [Abstract]
Short-term borrowings		604	304
Long-term debt due within one year		665	260
Accounts payable		693	598
Accrued expenses		337	331
Deferred income taxes		0	63
Regulatory liabilities		144	125
Mark-to-market derivative liabilities (current liabilities)		22	20
Other Liabilities, Current		68	73
Customer deposits		130	128
Due to Affiliate, Current		60	84
Total current liabilities		2,723	1,986
Long-term debt		5,435	5,698
Long-term debt to financing trusts		206	206
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,677	4,498
Asset retirement obligations		110	103
Non-pension postretirement benefit obligations		262	263
Regulatory liabilities		3,441	3,655
Mark-to-market derivative liabilities (noncurrent liabilities)		221	187
Other		954	889
Total deferred credits and other liabilities		9,665	9,595
Total liabilities		$ 18,029	$ 17,485
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 1,588	$ 1,588
Retained earnings		964	851
Other paid-in capital		5,548	5,468
Total shareholders’ equity		8,100	7,907
Total equity		8,100	7,907
Total liabilities and shareholders’ equity		26,129	25,392
PECO Energy Co [Member]
Assets, Current [Abstract]
Cash and cash equivalents		32	30
Restricted cash and cash equivalents		3	2
Accounts receivable, net
Customer		283	320
Other		122	141
Receivables from affiliates		4	3
Inventories, net
Fossil fuel and emission allowances		43	57
Materials and supplies		28	22
Deferred income taxes		69	69
Regulatory assets		32	29
Other		25	31
Prepaid utility taxes		42	10
Total current assets		683	714
Property, plant and equipment, net		7,027	6,801
Deferred debits and other assets
Regulatory assets		1,557	1,529
Investments		28	31
Other		36	34
Receivable from affiliate		388	490
Prepaid pension asset		353	344
Total deferred debits and other assets		2,362	2,428
Total assets		10,072	9,943
Liabilities, Current [Abstract]
Accounts payable		298	337
Accrued expenses		123	91
Regulatory liabilities		104	90
Other Liabilities, Current		30	31
Payables to affiliates		55	0
Customer deposits		56	52
Due to Affiliate, Current		53	52
Total current liabilities		719	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		2,752	2,671
Asset retirement obligations		26	29
Non-pension postretirement benefit obligations		288	287
Regulatory liabilities		536	657
Other		94	95
Total deferred credits and other liabilities		3,696	3,739
Total liabilities		$ 6,845	$ 6,822
Commitments and contingencies
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		$ 2,455	$ 2,439
Retained earnings		771	681
Accumulated other comprehensive loss, net	[2]	1	1
Total shareholders’ equity		3,227	3,121
Total equity		3,227	3,121
Total liabilities and shareholders’ equity		10,072	9,943
Member’s equity
Accumulated other comprehensive loss, net	[2]	1	1
Baltimore Gas and Electric Company [Member]
Assets, Current [Abstract]
Cash and cash equivalents		27	64
Restricted cash and cash equivalents		48	50
Accounts receivable, net
Customer		318	390
Other		77	82
Receivables from affiliates		1
Inventories, net
Fossil fuel and emission allowances		42	57
Materials and supplies		35	30
Deferred income taxes		8	6
Regulatory assets		257	214
Other		5	5
Prepaid utility taxes		4	59
Total current assets		822	957
Property, plant and equipment, net		6,459	6,204
Deferred debits and other assets
Regulatory assets		485	510
Investments		12	12
Other		25	25
Prepaid pension asset		331	370
Total deferred debits and other assets		853	917
Total assets	[4]	8,134	8,078
Liabilities, Current [Abstract]
Short-term borrowings		50	120
Long-term debt due within one year		77	75
Accounts payable		201	215
Accrued expenses		159	131
Deferred income taxes		63	52
Regulatory liabilities		69	44
Other Liabilities, Current		32	51
Customer deposits		99	92
Due to Affiliate, Current		47	66
Total current liabilities		797	846
Long-term debt		1,828	1,867
Long-term debt to financing trusts		258	258
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		1,937	1,865
Asset retirement obligations		15	17
Non-pension postretirement benefit obligations		209	212
Regulatory liabilities		186	200
Other		59	60
Total deferred credits and other liabilities		2,406	2,354
Total liabilities	[4]	5,289	5,325
Stockholders' Equity Attributable to Parent [Abstract]
Common stock		1,366	1,360
Retained earnings		1,289	1,203
Total shareholders’ equity		2,655	2,563
BGE preference stock not subject to mandatory redemption		190	190
Total equity		2,845	2,753
Total liabilities and shareholders' equity		8,134	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		$ 162	$ 197	[4]

[1] Exelon’s consolidated assets include $8,190 million and $8,160 million at September 30, 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 $3,242 million and $2,723 million at September 30, 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 $8,130 million and $8,119 million at September 30, 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 $3,070 million and $2,507 million at September 30, 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 September 30, 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 $162 million and $197 million at September 30, 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.