Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Sep. 30, 2016	Mar. 23, 2016	Dec. 31, 2015		Sep. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 1,897		$ 6,502		$ 7,265	$ 1,878
Restricted cash		321		205
Accounts receivable, net
Customer		4,061		3,187
Other		1,013		912
Derivative Asset, Current		754		1,365
Inventory
Materials and supplies		1,188		1,104
Other current assets		1,064		752
Total current assets		12,208		15,334
Property, plant and equipment, net		71,214		57,439
Nuclear decommissioning trust funds		11,076		10,342
Goodwill		6,672		2,672
Derivative Asset, Noncurrent		669		758
Other noncurrent assets		1,474		1,445
Total assets		114,535		95,384
Short-term borrowings		567		533
Long-term debt due within one year		2,512		1,500
Accounts payable		3,044		2,883
Accrued expenses		3,236		2,376
Mark-to-market derivative liabilities (current liabilities)		222		205
Other current liabilities		452		100
Other		1,068		842
Total current liabilities		12,158		9,118
Long-term debt		32,330		23,645
Asset retirement obligations		9,348		8,585
Pension obligation(c)		3,765		3,385
Energy Marketing Contract Liabilities, Noncurrent		927		117
Other noncurrent liabilities		1,928		1,491
Total liabilities	[1]	87,049		68,062
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		160		164
Restricted cash		101		100
Accounts receivable, net
Customer		264		219
Other		42		43
Derivative Asset, Current		49		140
Inventory
Materials and supplies		192		181
Other current assets		58		35
Total current assets		866		882
Property, plant and equipment, net		5,139		5,160
Nuclear decommissioning trust funds		2,173		2,036
Goodwill		47		47
Derivative Asset, Noncurrent		32		53
Other noncurrent assets		257		90
Total noncurrent assets		7,648		7,386
Total assets		8,514		8,268
Long-term debt due within one year		191		111
Accounts payable		201		216
Accrued expenses		102		115
Mark-to-market derivative liabilities (current liabilities)		24		5
Other current liabilities		14		12
Other		34		13
Total current liabilities		566		472
Long-term debt		661		666
Asset retirement obligations	[2]	2,070		1,999
Pension obligation(c)		9		9
Energy Marketing Contract Liabilities, Noncurrent		26		39
Other noncurrent liabilities		106		79
Total deferred credits and other liabilities		2,872		2,792
Total liabilities		3,438		3,264
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		375		431		545	780
Restricted cash		162		123
Accounts receivable, net
Customer		2,318		2,095
Other		301		360
Derivative Asset, Current		754		1,365
Inventory
Materials and supplies		849		880
Other current assets		788		535
Total current assets		6,135		6,342
Property, plant and equipment, net		26,374		25,843
Nuclear decommissioning trust funds		11,076		10,342
Goodwill		47		47
Derivative Asset, Noncurrent		630		733
Other noncurrent assets		692		627
Total assets		47,568		46,529
Short-term borrowings		40		29
Long-term debt due within one year		254		90
Accounts payable		1,465		1,583
Accrued expenses		942		935
Mark-to-market derivative liabilities (current liabilities)		203		182
Other current liabilities		76		100
Other		392		356
Total current liabilities		4,307		4,933
Long-term debt		8,077		7,936
Asset retirement obligations		9,160		8,431
Energy Marketing Contract Liabilities, Noncurrent		97		117
Other noncurrent liabilities		691		602
Total liabilities	[3]	33,829		33,559
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		160		164
Restricted cash		43		77
Accounts receivable, net
Customer		264		219
Other		42		43
Derivative Asset, Current		49		140
Inventory
Materials and supplies		192		181
Other current assets		51		30
Total current assets		801		854
Property, plant and equipment, net		5,139		5,160
Nuclear decommissioning trust funds		2,173		2,036
Goodwill		47		47
Derivative Asset, Noncurrent		32		53
Other noncurrent assets		223		85
Total noncurrent assets		7,614		7,381
Total assets		8,415		8,235
Long-term debt due within one year		64		27
Accounts payable		201		216
Accrued expenses		98		113
Mark-to-market derivative liabilities (current liabilities)		24		5
Other current liabilities		14		12
Other		34		13
Total current liabilities		435		386
Long-term debt		550		623
Asset retirement obligations		2,070		1,999	[2]
Pension obligation(c)		9		9
Energy Marketing Contract Liabilities, Noncurrent		26		39
Other noncurrent liabilities		106		79
Total deferred credits and other liabilities		2,761		2,749
Total liabilities		3,196		3,135
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		341		9		27	64
Restricted cash		46		24
Accounts receivable, net
Customer		332		300
Other		100		112
Inventory
Materials and supplies		39		33
Other current assets		5		3
Total current assets		1,114		845
Property, plant and equipment, net		6,904		6,597
Other noncurrent assets		9		8
Total assets	[4]	8,857		8,295
Short-term borrowings		0		210
Long-term debt due within one year		381		378
Accounts payable		239		209
Accrued expenses		144		110
Other		35		35
Total current liabilities		1,003		1,134
Long-term debt		2,281		1,480
Asset retirement obligations		21		17
Other noncurrent liabilities		72		61
Total liabilities	[4]	6,100		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		44		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		44		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		47		26
Long-term debt due within one year		81		79
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		83		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		83		122
Pepco Holdings LLC [Member]
Inventory
Goodwill		4,000		0
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			$ 319	26		272	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		299	$ 319
Restricted cash		49
Accounts receivable, net
Customer		595
Other		345
Derivative Asset, Current		0
Inventory
Materials and supplies		118
Other current assets		54
Total current assets		2,118
Property, plant and equipment, net		11,311
Goodwill		4,000
Derivative Asset, Noncurrent		0
Other noncurrent assets		76
Total assets		21,063
Short-term borrowings		517
Long-term debt due within one year		545
Accounts payable		335
Accrued expenses		325
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		376
Other		36
Total current liabilities		2,547
Long-term debt		5,499
Asset retirement obligations		14
Pension obligation(c)		0
Energy Marketing Contract Liabilities, Noncurrent		830
Other noncurrent liabilities		234
Total liabilities		13,176
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		15
Accounts receivable, net
Customer		0
Other		0
Derivative Asset, Current		0
Inventory
Materials and supplies		0
Other current assets		5
Total current assets		20
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		51
Long-term debt due within one year		43
Accounts payable		0
Accrued expenses		2
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		0
Other		0
Total current liabilities		45
Long-term debt		111
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		111
Total liabilities		156
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		165		3		$ 4	$ 2
Restricted cash		15		12
Accounts receivable, net
Customer		168		156
Other		46		242
Inventory
Materials and supplies		22		23
Other current assets		3		12
Total current assets		520		546
Property, plant and equipment, net		2,456		2,322
Other noncurrent assets		42		19
Total assets		3,507		3,387
Short-term borrowings		0		5
Long-term debt due within one year		38		48
Accounts payable		110		96
Accrued expenses		72		70
Other		7		14
Total current liabilities		338		297
Long-term debt		1,129		1,153
Other noncurrent liabilities		31		12
Total liabilities		2,442		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		15		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		15		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		34		30
Long-term debt due within one year		38		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		40		48
Long-term debt		99		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		99		124
Total liabilities		$ 139		$ 172

[1] Exelon’s consolidated assets include $8,514 million and $8,268 million at September 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 $3,438 million and $3,264 million at September 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 $8,415 million and $8,235 million at September 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 $3,196 million and $3,135 million at September 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 $47 million and $26 million at September 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 $83 million and $122 million at September 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.