Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Jun. 30, 2016	Mar. 23, 2016	Dec. 31, 2015		Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,647		$ 6,502		$ 6,014	$ 1,878
Restricted cash		201		205
Accounts receivable, net
Customer		3,671		3,187
Other		988		912
Derivative Asset, Current		759		1,365
Inventory
Materials and supplies		1,183		1,104
Other current assets		1,101		752
Total current assets		11,495		15,334
Property, plant and equipment, net		70,693		57,439
Nuclear decommissioning trust funds		10,737		10,342
Goodwill		6,696		2,672
Derivative Asset, Noncurrent		546		758
Other noncurrent assets		1,366		1,445
Total assets		112,778		95,384
Short-term borrowings		951		533
Long-term debt due within one year		2,693		1,500
Accounts payable		2,826		2,883
Accrued expenses		2,757		2,376
Mark-to-market derivative liabilities (current liabilities)		152		205
Other current liabilities		508		100
Other		1,025		842
Total current liabilities		11,894		9,118
Long-term debt		31,541		23,645
Asset retirement obligations		9,256		8,585
Pension obligation(c)		3,767		3,385
Energy Marketing Contract Liabilities, Noncurrent		1,011		117
Other noncurrent liabilities		1,876		1,491
Total liabilities	[1]	85,456		68,062
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		138		164
Restricted cash		53		100
Accounts receivable, net
Customer		253		219
Other		44		43
Derivative Asset, Current		41		140
Inventory
Materials and supplies		189		181
Other current assets		37		35
Total current assets		755		882
Property, plant and equipment, net		5,147		5,160
Nuclear decommissioning trust funds		2,100		2,036
Goodwill		47		47
Derivative Asset, Noncurrent		24		53
Other noncurrent assets		167		90
Total noncurrent assets		7,485		7,386
Total assets		8,240		8,268
Long-term debt due within one year		312		111
Accounts payable		146		216
Accrued expenses		79		115
Mark-to-market derivative liabilities (current liabilities)		21		5
Other current liabilities		13		12
Other		23		13
Total current liabilities		594		472
Long-term debt		675		666
Asset retirement obligations	[2]	2,053		1,999
Pension obligation(c)		9		9
Energy Marketing Contract Liabilities, Noncurrent		31		39
Other noncurrent liabilities		99		79
Total deferred credits and other liabilities		2,867		2,792
Total liabilities		3,461		3,264
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		373		431		456	780
Restricted cash		98		123
Accounts receivable, net
Customer		2,076		2,095
Other		325		360
Derivative Asset, Current		759		1,365
Inventory
Materials and supplies		840		880
Other current assets		735		535
Total current assets		5,725		6,342
Property, plant and equipment, net		26,656		25,843
Nuclear decommissioning trust funds		10,737		10,342
Goodwill		47		47
Derivative Asset, Noncurrent		499		733
Other noncurrent assets		632		627
Total assets		46,897		46,529
Short-term borrowings		208		29
Long-term debt due within one year		174		90
Accounts payable		1,271		1,583
Accrued expenses		743		935
Mark-to-market derivative liabilities (current liabilities)		134		182
Other current liabilities		75		100
Other		339		356
Total current liabilities		4,187		4,933
Long-term debt		7,965		7,936
Asset retirement obligations		9,081		8,431
Energy Marketing Contract Liabilities, Noncurrent		94		117
Other noncurrent liabilities		634		602
Total liabilities	[3]	33,530		33,559
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		138		164
Restricted cash		26		77
Accounts receivable, net
Customer		253		219
Other		44		43
Derivative Asset, Current		41		140
Inventory
Materials and supplies		189		181
Other current assets		30		30
Total current assets		721		854
Property, plant and equipment, net		5,147		5,160
Nuclear decommissioning trust funds		2,100		2,036
Goodwill		47		47
Derivative Asset, Noncurrent		24		53
Other noncurrent assets		133		85
Total noncurrent assets		7,451		7,381
Total assets		8,172		8,235
Long-term debt due within one year		183		27
Accounts payable		146		216
Accrued expenses		76		113
Mark-to-market derivative liabilities (current liabilities)		21		5
Other current liabilities		13		12
Other		23		13
Total current liabilities		462		386
Long-term debt		557		623
Asset retirement obligations		2,053		1,999	[2]
Pension obligation(c)		9		9
Energy Marketing Contract Liabilities, Noncurrent		31		39
Other noncurrent liabilities		99		79
Total deferred credits and other liabilities		2,749		2,749
Total liabilities		3,211		3,135
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		5		9		24	64
Restricted cash		19		24
Accounts receivable, net
Customer		289		300
Other		70		112
Inventory
Materials and supplies		41		33
Other current assets		7		3
Total current assets		714		845
Property, plant and equipment, net		6,747		6,597
Other noncurrent assets		9		8
Total assets		8,325		8,295
Short-term borrowings		208		210
Long-term debt due within one year		380		378
Accounts payable		222		209
Accrued expenses		101		110
Other		30		35
Total current liabilities		1,165		1,134
Long-term debt		1,440		1,480
Asset retirement obligations		15		17
Other noncurrent liabilities		71		61
Total liabilities	[4]	5,395		5,418
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		17		23
Accounts receivable, net
Customer		0		0
Other		0		0
Derivative Asset, Current		0		0
Inventory
Materials and supplies		0		0
Other current assets		0		0
Total current assets		17		23
Property, plant and equipment, net		0		0
Nuclear decommissioning trust funds		0		0
Goodwill		0		0
Derivative Asset, Noncurrent		0		0
Other noncurrent assets		3		3
Total noncurrent assets		3		3
Total assets		20		26
Long-term debt due within one year		81		79
Accounts payable		0		0
Accrued expenses		1		2
Mark-to-market derivative liabilities (current liabilities)		0		0
Other current liabilities		0		0
Other		0		0
Total current liabilities		82		81
Long-term debt				41
Asset retirement obligations		0		0
Pension obligation(c)	[2]	0		0
Energy Marketing Contract Liabilities, Noncurrent		0		0
Other noncurrent liabilities		0		0
Total deferred credits and other liabilities		0		41
Total liabilities		82		122
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			$ 319	26		34	15
Restricted cash				14
Accounts receivable, net
Customer				581
Other				319
Derivative Asset, Current				18
Inventory
Materials and supplies				122
Other current assets				80
Total current assets				1,474
Property, plant and equipment, net				10,864
Goodwill				1,406
Derivative Asset, Noncurrent				0
Other noncurrent assets				69
Total assets				16,188
Short-term borrowings				958
Long-term debt due within one year				456
Accounts payable				404
Accrued expenses				266
Mark-to-market derivative liabilities (current liabilities)				0
Other current liabilities				0
Other				70
Total current liabilities				2,327
Long-term debt				4,823
Asset retirement obligations				8
Pension obligation(c)				466
Energy Marketing Contract Liabilities, Noncurrent				0
Other noncurrent liabilities				200
Total liabilities				11,592
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		294	$ 319
Restricted cash		44
Accounts receivable, net
Customer		501
Other		237
Derivative Asset, Current		0
Inventory
Materials and supplies		121
Other current assets		87
Total current assets		2,019
Property, plant and equipment, net		11,148
Goodwill		4,024
Derivative Asset, Noncurrent		0
Other noncurrent assets		57
Total assets		20,921
Short-term borrowings		500
Long-term debt due within one year		551
Accounts payable		344
Accrued expenses		306
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		433
Other		31
Total current liabilities		2,636
Long-term debt		5,522
Asset retirement obligations		12
Pension obligation(c)		0
Energy Marketing Contract Liabilities, Noncurrent		918
Other noncurrent liabilities		280
Total liabilities		13,150
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents				0
Restricted cash				12
Accounts receivable, net
Customer				0
Other				0
Derivative Asset, Current				0
Inventory
Materials and supplies				0
Other current assets				0
Total current assets				12
Property, plant and equipment, net				0
Nuclear decommissioning trust funds				0
Goodwill				0
Derivative Asset, Noncurrent				0
Other noncurrent assets				18
Total noncurrent assets				18
Total assets				30
Long-term debt due within one year				46
Accounts payable				0
Accrued expenses				2
Mark-to-market derivative liabilities (current liabilities)				0
Other current liabilities				0
Other				0
Total current liabilities				48
Long-term debt				124
Asset retirement obligations				0
Pension obligation(c)	[2]			0
Energy Marketing Contract Liabilities, Noncurrent				0
Other noncurrent liabilities				0
Total deferred credits and other liabilities				124
Total liabilities				172
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0
Restricted cash		10
Accounts receivable, net
Customer		0
Other		0
Derivative Asset, Current		0
Inventory
Materials and supplies		0
Other current assets		4
Total current assets		14
Property, plant and equipment, net		0
Nuclear decommissioning trust funds		0
Goodwill		0
Derivative Asset, Noncurrent		0
Other noncurrent assets		31
Total noncurrent assets		31
Total assets		45
Long-term debt due within one year		46
Accounts payable		0
Accrued expenses		2
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		0
Other		0
Total current liabilities		48
Long-term debt		118
Asset retirement obligations		0
Pension obligation(c)	[2]	0
Energy Marketing Contract Liabilities, Noncurrent		0
Other noncurrent liabilities		0
Total deferred credits and other liabilities		118
Total liabilities		166
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		151		3		$ 3	$ 2
Restricted cash		10		12
Accounts receivable, net
Customer		122		156
Other		69		242
Inventory
Materials and supplies		23		23
Other current assets		4		12
Total current assets		513		546
Property, plant and equipment, net		2,427		2,322
Other noncurrent assets		23		19
Total assets		3,461		3,387
Short-term borrowings		0		5
Long-term debt due within one year		44		48
Accounts payable		107		96
Accrued expenses		86		70
Other		7		14
Total current liabilities		375		297
Long-term debt		1,136		1,153
Other noncurrent liabilities		23		12
Total liabilities		2,430		2,387
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0		0
Restricted cash		10		12
Accounts receivable, net
Customer		0		0
Other		0		0
Derivative Asset, Current		0		0
Inventory
Materials and supplies		0		0
Other current assets		0		0
Total current assets		10		12
Property, plant and equipment, net		0		0
Nuclear decommissioning trust funds		0		0
Goodwill		0		0
Derivative Asset, Noncurrent		0		0
Other noncurrent assets		19		18
Total noncurrent assets		19		18
Total assets		29		30
Long-term debt due within one year		42		46
Accounts payable		0		0
Accrued expenses		2		2
Mark-to-market derivative liabilities (current liabilities)		0		0
Other current liabilities		0		0
Other		0		0
Total current liabilities		44		48
Long-term debt		106		124
Asset retirement obligations		0		0
Pension obligation(c)	[2]	0		0
Energy Marketing Contract Liabilities, Noncurrent		0		0
Other noncurrent liabilities		0		0
Total deferred credits and other liabilities		106		124
Total liabilities		$ 150		$ 172

[1] Exelon’s consolidated assets include $8,240 million and $8,268 million at June 30, 2016 and December 31, 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,461 million and $3,264 million at June 30, 2016 and December 31, 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 3 - Variable Interest Entities.

[2] Includes the 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 13 - Retirement Benefits for additional details.

[3] Generation’s consolidated assets include $8,172 million and $8,235 million at June 30, 2016 and December 31, 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,211 million and $3,135 million at June 30, 2016 and December 31, 2015, 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 $20 million and $26 million at June 30, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $82 million and $122 million at June 30, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 - Variable Interest Entities.