Consolidated Balance Sheets (Unaudited) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents		$ 6,502	$ 1,878
Cash and cash equivalents		6,502	1,878
Restricted cash and cash equivalents		205	271
Accounts receivable, net
Customer		3,187	3,482
Other		912	1,227
Mark-to-market derivative assets		1,365	1,279
Unamortized energy contract assets		86	254
Inventories, net
Fossil fuel		462	579
Materials and supplies		1,104	1,024
Regulatory assets		759	847
Assets held for sale		4	147
Other		748	865
Total current assets		15,334	11,853
Property, plant and equipment, net		57,439	52,170
Deferred debits and other assets
Regulatory assets		6,065	6,076
Nuclear decommissioning trust funds		10,342	10,537
Investments		639	544
Goodwill		2,672	2,672
Mark-to-market derivative assets		758	773
Unamortized energy contract assets		484	549
Pledged assets for Zion Station decommissioning		206	319
Other		1,445	923
Total deferred debits and other assets		22,611	22,393
Total assets	[1]	95,384	86,416
Current liabilities
Short-term borrowings		533	460
Long-term debt due within one year		1,500	1,802
Accounts payable		2,883	3,048
Accrued expenses		2,376	1,539
Payables to affiliates		8	8
Accounts Payable, Related Parties, Current		8	8
Mark-to-market derivative liabilities		205	234
Unamortized energy contract liabilities		100	238
Energy Marketing Accounts Payable		302	192
Regulatory liabilities		369	310
Other		842	931
Total current liabilities		9,118	8,762
Long-term debt		23,645	19,212
Long-term debt to financing trusts	[2]	641	641
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		13,776	12,778
Asset retirement obligations		8,585	7,295
Pension obligations		3,385	3,366
Non-pension postretirement benefit obligations		1,618	1,742
Spent nuclear fuel obligation		1,021	1,021
Regulatory liabilities		4,201	4,550
Mark-to-market derivative liabilities		374	403
Unamortized energy contract liabilities		117	211
Payable for Zion Station decommissioning		90	155
Other		1,491	2,147
Total deferred credits and other liabilities		34,658	33,668
Total liabilities	[1]	68,062	62,283
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount		28	0
Shareholders’ equity
Common stock		18,676	16,709
Treasury stock, at cost (35 shares at December 31, 2015 and 2014, respectively)		(2,327)	(2,327)
Retained earnings		12,068	10,910
Accumulated other comprehensive loss, net		(2,624)	(2,684)	[3]
Total shareholders’ equity		25,793	22,608
BGE preference stock not subject to mandatory redemption		193	193
Noncontrolling interest		1,308	1,332
Total equity		27,294	24,133
Total liabilities and shareholders’ equity		95,384	86,416
Member’s equity
Accumulated other comprehensive loss, net		(2,624)	(2,684)	[3]
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,268	8,159
Deferred credits and other liabilities
Total liabilities		3,264	2,728
Commonwealth Edison Co [Member]
Current assets
Cash and cash equivalents		67	66
Restricted cash and cash equivalents		2	4
Accounts receivable, net
Customer		533	477
Other		272	648
Receivables from affiliates		199	14
Inventories, net
Inventories, net		164	125
Regulatory assets		218	349
Other		63	40
Total current assets		1,518	1,723
Property, plant and equipment, net		17,502	15,793
Deferred debits and other assets
Regulatory assets		895	852
Investments		6	6
Goodwill		2,625	2,625
Receivable from affiliates		2,172	2,571
Prepaid pension asset		1,490	1,551
Other		324	237
Total deferred debits and other assets		7,512	7,842
Total assets		26,532	25,358
Current liabilities
Short-term borrowings		294	304
Long-term debt due within one year		665	260
Accounts payable		660	598
Accrued expenses		706	331
Accounts Payable, Related Parties, Current		62	84
Mark-to-market derivative liabilities		23	20
Customer deposits		131	128
Regulatory liabilities		155	125
Other		70	73
Total current liabilities		2,766	1,923
Long-term debt		5,844	5,665
Long-term debt to financing trusts		205	205
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		4,914	4,561
Asset retirement obligations		111	103
Non-pension postretirement benefit obligations		259	263
Regulatory liabilities		3,459	3,655
Mark-to-market derivative liabilities		224	187
Other		507	889
Total deferred credits and other liabilities		9,474	9,658
Total liabilities		18,289	17,451
Shareholders’ equity
Common stock		1,588	1,588
Other paid-in capital		5,677	5,468
Retained earnings		978	851
Total shareholders’ equity		8,243	7,907
Total liabilities and shareholders’ equity		26,532	25,358
Exelon Generation Co L L C [Member]
Current assets
Cash and cash equivalents		431	780
Cash and cash equivalents		431	780
Restricted cash and cash equivalents		123	158
Accounts receivable, net
Customer		2,095	2,295
Other		360	318
Mark-to-market derivative assets		1,365	1,276
Receivables from affiliates		83	113
Unamortized energy contract assets		86	254
Inventories, net
Fossil fuel		384	465
Materials and supplies		880	847
Assets held for sale		4	147
Other		531	658
Total current assets		6,342	7,311
Property, plant and equipment, net		25,843	23,028
Deferred debits and other assets
Nuclear decommissioning trust funds		10,342	10,537
Investments		210	104
Goodwill		47	47
Mark-to-market derivative assets		733	771
Prepaid pension asset		1,689	1,704
Unamortized energy contract assets		484	549
Deferred income taxes		6	3
Pledged assets for Zion Station decommissioning		206	319
Other		627	578
Total deferred debits and other assets		14,344	14,612
Total assets	[4]	46,529	44,951
Current liabilities
Short-term borrowings		29	36
Long-term debt due within one year		90	58
Accounts payable		1,583	1,759
Accrued expenses		935	886
Payables to affiliates		0	556
Accounts Payable, Related Parties, Current		104	107
Mark-to-market derivative liabilities		182	214
Unamortized energy contract liabilities		100	238
Energy Marketing Accounts Payable		302	192
Other		356	413
Exelon Money Pool Borrowing Current		1,252	0
Total current liabilities		4,933	4,459
Long-term debt		7,936	6,639
Long-term debt to financing trusts		933	943
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		5,845	5,707
Asset retirement obligations		8,431	7,146
Non-pension postretirement benefit obligations		924	915
Spent nuclear fuel obligation		1,021	1,021
Mark-to-market derivative liabilities		150	105
Unamortized energy contract liabilities		117	211
Payable for Zion Station decommissioning		90	155
Other		602	719
Due to Affiliate, Noncurrent		2,577	2,880
Total deferred credits and other liabilities		19,757	18,859
Total liabilities	[4]	33,559	30,900
Redeemable Noncontrolling Interest, Equity, Common, Carrying Amount		28
Shareholders’ equity
Accumulated other comprehensive loss, net		(63)	(36)	[3]
Noncontrolling interest		1,307	1,333
Member’s equity
Membership interest		8,997	8,951
Undistributed earnings		2,701	3,803
Accumulated other comprehensive loss, net		(63)	(36)	[3]
Total member’s equity		11,635	12,718
Total equity		12,942	14,051
Total liabilities and equity		46,529	44,951
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		8,235	8,118
Deferred credits and other liabilities
Total liabilities		3,135	2,512
PECO Energy Co [Member]
Current assets
Cash and cash equivalents		295	30
Restricted cash and cash equivalents		3	2
Accounts receivable, net
Customer		258	320
Other		146	141
Receivables from affiliates		2	3
Inventories, net
Fossil fuel		43	57
Materials and supplies		26	22
Prepaid utility taxes		11	10
Regulatory assets		34	29
Other		24	31
Total current assets		842	645
Property, plant and equipment, net		7,141	6,801
Deferred debits and other assets
Regulatory assets		1,583	1,529
Investments		28	31
Receivable from affiliates		405	490
Prepaid pension asset		347	344
Other		21	20
Total deferred debits and other assets		2,384	2,414
Total assets		10,367	9,860
Current liabilities
Long-term debt due within one year		300	0
Accounts payable		281	337
Accrued expenses		109	91
Accounts Payable, Related Parties, Current		55	52
Customer deposits		58	52
Regulatory liabilities		112	90
Other		29	31
Total current liabilities		944	653
Long-term debt		2,280	2,232
Long-term debt to financing trusts		184	184
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,792	2,602
Asset retirement obligations		27	29
Non-pension postretirement benefit obligations		287	287
Regulatory liabilities		527	657
Mark-to-market derivative liabilities		12
Other		90	95
Total deferred credits and other liabilities		3,723	3,670
Total liabilities		7,131	6,739
Shareholders’ equity
Common stock		2,455	2,439
Retained earnings		780	681
Accumulated other comprehensive loss, net		1	1	[3]
Total shareholders’ equity		3,236	3,121
Total liabilities and shareholders’ equity		10,367	9,860
Member’s equity
Accumulated other comprehensive loss, net		1	1	[3]
Baltimore Gas and Electric Company [Member]
Current assets
Cash and cash equivalents		9	64
Restricted cash and cash equivalents		24	50
Accounts receivable, net
Customer		300	390
Other		112	82
Inventories, net
Fossil fuel		36	57
Materials and supplies		33	30
Prepaid utility taxes		61	59
Regulatory assets		267	214
Other		3	5
Total current assets		845	951
Property, plant and equipment, net		6,597	6,204
Deferred debits and other assets
Regulatory assets		514	510
Investments		12	12
Prepaid pension asset		319	370
Other		8	9
Total deferred debits and other assets		853	901
Total assets	[5]	8,295	8,056
Current liabilities
Short-term borrowings		210	120
Long-term debt due within one year		378	75
Accounts payable		209	215
Accrued expenses		110	131
Accounts Payable, Related Parties, Current		52	66
Customer deposits		102	92
Regulatory liabilities		38	44
Other		35	51
Total current liabilities		1,134	794
Long-term debt		1,480	1,857
Long-term debt to financing trusts		252	252
Deferred credits and other liabilities
Deferred income taxes and unamortized investment tax credits		2,081	1,911
Asset retirement obligations		17	17
Non-pension postretirement benefit obligations		209	212
Regulatory liabilities		184	200
Other		61	60
Total deferred credits and other liabilities		2,552	2,400
Total liabilities	[5]	5,418	5,303
Shareholders’ equity
Common stock		1,367	1,360
Retained earnings		1,320	1,203
Total shareholders’ equity		2,687	2,563
BGE preference stock not subject to mandatory redemption		190	190
Total equity		2,877	2,753
Total liabilities and shareholders’ equity		8,295	8,056
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure [Member]
Deferred debits and other assets
Total assets		26	24
Deferred credits and other liabilities
Total liabilities		122	$ 197
Constellation Energy Group LLC [Member]
Deferred debits and other assets
Total assets		$ 187

[1] 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.

[2] Amounts owed to these financing trusts are recorded as Long-term debt to financing trusts within Exelon’s Consolidated Balance Sheets.

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

[4] 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.

[5] 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.