Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 6,014	$ 1,878	$ 1,362	$ 1,609
Restricted cash		274	271
Accounts receivable, net
Customer		3,227	3,482
Other		1,304	1,227
Inventory
Materials and supplies		1,068	1,024
Other current assets		654	865
Mark-to-market derivative assets (current assets)		1,405	1,279
Total current assets		15,425	12,097
Property, plant and equipment, net		53,935	52,087
Nuclear decommissioning trust funds		10,607	10,537
Goodwill		2,672	2,672
Mark-to-market derivative assets		811	773
Other noncurrent assets		1,388	1,160
Total assets		92,213	86,814
Short-term borrowings		543	460
Long-term debt due within one year		226	1,802
Accounts payable		2,727	3,048
Accrued expenses		1,366	1,539
Mark-to-market derivative liabilities (current liabilities)		165	234
Other current liabilities		141	238
Other Liabilities, Current		941	1,123
Total current liabilities		6,526	8,762
Long-term debt		25,220	19,362
Asset retirement obligations		7,550	7,295
Pension obligation(a)		3,134	3,366
Energy Marketing Contract Liabilities, Noncurrent		166	211
Other noncurrent liabilities		2,528	2,147
Total deferred credits and other liabilities		34,750	33,909
Total liabilities	[1]	67,144	62,681
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		240	392
Restricted cash		145	117
Accounts receivable, net
Customer		179	297
Other		29	57
Inventory
Materials and supplies		178	172
Other current assets		32	33
Mark-to-market derivative assets (current assets)		96	171
Total current assets		899	1,239
Property, plant and equipment, net		4,811	4,638
Nuclear decommissioning trust funds		2,096	2,097
Goodwill		47	47
Mark-to-market derivative assets		45	44
Other noncurrent assets		91	95
Total noncurrent assets		7,090	6,921
Total assets		7,989	8,160
Long-term debt due within one year		88	87
Accounts payable		143	292
Accrued expenses		87	111
Mark-to-market derivative liabilities (current liabilities)		8	24
Other current liabilities		9	22
Other Liabilities, Current		13	25
Total current liabilities		348	561
Long-term debt		166	212
Asset retirement obligations		1,865	1,763
Pension obligation(a)	[2]	9	9
Energy Marketing Contract Liabilities, Noncurrent		45	51
Other noncurrent liabilities		122	127
Total deferred credits and other liabilities		2,207	2,162
Total liabilities		2,555	2,723
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		456	780	305	1,258
Restricted cash		174	158
Accounts receivable, net
Customer		2,045	2,295
Other		299	318
Inventory
Materials and supplies		860	847
Other current assets		451	658
Mark-to-market derivative assets (current assets)		1,405	1,276
Total current assets		6,443	7,638
Property, plant and equipment, net		23,766	22,945
Nuclear decommissioning trust funds		10,607	10,537
Goodwill		47	47
Mark-to-market derivative assets		790	771
Other noncurrent assets		798	731
Total assets	[3]	45,125	45,348
Short-term borrowings		40	36
Long-term debt due within one year		89	58
Accounts payable		1,528	1,759
Accrued expenses		732	886
Mark-to-market derivative liabilities (current liabilities)		145	214
Other current liabilities		141	238
Other Liabilities, Current		453	605
Total current liabilities		3,864	4,459
Long-term debt		7,974	6,709
Asset retirement obligations		7,399	7,146
Energy Marketing Contract Liabilities, Noncurrent		166	211
Other noncurrent liabilities		817	719
Total deferred credits and other liabilities		19,693	19,186
Total liabilities	[3]	32,469	31,297
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		240	392
Restricted cash		121	96
Accounts receivable, net
Customer		179	297
Other		29	57
Inventory
Materials and supplies		178	172
Other current assets		25	26
Mark-to-market derivative assets (current assets)		96	171
Total current assets		868	1,211
Property, plant and equipment, net		4,811	4,638
Nuclear decommissioning trust funds		2,096	2,097
Goodwill		47	47
Mark-to-market derivative assets		45	44
Other noncurrent assets		82	82
Total noncurrent assets		7,081	6,908
Total assets		7,949	8,119
Long-term debt due within one year		5	5
Accounts payable		143	292
Accrued expenses		84	108
Mark-to-market derivative liabilities (current liabilities)		8	24
Other current liabilities		9	22
Other Liabilities, Current		13	25
Total current liabilities		262	476
Long-term debt		79	81
Asset retirement obligations		1,865	1,763
Pension obligation(a)	[2]	9	9
Energy Marketing Contract Liabilities, Noncurrent		45	51
Other noncurrent liabilities		122	127
Total deferred credits and other liabilities		2,120	2,031
Total liabilities		2,382	2,507
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		24	64	$ 15	$ 31
Restricted cash		29	50
Accounts receivable, net
Customer		360	390
Other		76	82
Inventory
Materials and supplies		35	30
Other current assets		4	5
Total current assets		776	957
Property, plant and equipment, net		6,373	6,204
Other noncurrent assets		25	25
Total assets	[4]	8,017	8,078
Short-term borrowings		0	120
Long-term debt due within one year		77	75
Accounts payable		194	215
Accrued expenses		108	131
Other Liabilities, Current		33	51
Total current liabilities		700	846
Long-term debt		1,828	1,867
Asset retirement obligations		18	17
Other noncurrent liabilities		62	60
Total deferred credits and other liabilities		2,404	2,354
Total liabilities	[4]	5,190	5,325
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash		24	21
Accounts receivable, net
Customer		0	0
Other		0	0
Inventory
Materials and supplies		0	0
Other current assets		0	0
Mark-to-market derivative assets (current assets)		0	0
Total current assets		24	21
Property, plant and equipment, net		0	0
Nuclear decommissioning trust funds		0	0
Goodwill		0	0
Mark-to-market derivative assets		0	0
Other noncurrent assets		3	3
Total noncurrent assets		3	3
Total assets		27	24
Long-term debt due within one year		77	75
Accounts payable		0	0
Accrued expenses		1	2
Mark-to-market derivative liabilities (current liabilities)		0	0
Other current liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		78	77
Long-term debt		81	120
Asset retirement obligations		0	0
Pension obligation(a)		0	0
Energy Marketing Contract Liabilities, Noncurrent		0	0
Other noncurrent liabilities		0	0
Total deferred credits and other liabilities		81	120
Total liabilities		$ 159	$ 197

[1] Exelon’s consolidated assets include $7,989 million and $8,160 million at June 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 $2,555 million and $2,723 million at June 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] Includes CNEG retail gas pension obligation, which is presented as a net asset balance within the Prepaid Pension asset line item on Generation’s balance sheet. See Note 14 — Retirement Benefits for additional details.

[3] Generation’s consolidated assets include $7,949 million and $8,119 million at June 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 $2,435 million and $2,507 million at June 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 $27 million and $24 million at June 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 $160 million and $197 million at June 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.