Variable Interest Entities - Assets and Liabilities of VIEs which Creditors or Beneficiaries have No Recourse (Details) - USD ($) $ in Millions		Dec. 31, 2016	Mar. 23, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 635		$ 6,502	$ 1,878	$ 1,609
Customer		4,158		3,187
Other		1,201		912
Mark-to-market derivative assets		917		1,365
Materials and supplies		1,274		1,104
Other current assets		930		752
Total current assets		12,412		15,334
Property, plant and equipment, net		71,555		57,439
Nuclear decommissioning trust funds		11,061		10,342
Goodwill		6,677		2,672	2,672
Mark-to-market derivative assets		492		758
Other noncurrent assets		1,472		1,445
Deferred Costs and Other Assets		30,937		22,611
Total assets (a)	[1]	114,904		95,384
Long-term debt due within one year		2,430		1,500
Accounts payable		3,441		2,883
Accrued expenses		3,460		2,376
Mark-to-market derivative liabilities		282		205
Energy Marketing Contract Liabilities, Current		407		100
Other current liabilities		981		842
Total current liabilities		13,457		9,118
Long-term debt		31,575		23,645
Asset retirement obligations		9,111		8,585
Pension obligations		4,248		3,385
Energy Marketing Contract Liabilities, Noncurrent		830		117
Other noncurrent liabilities		1,827		1,491
Total liabilities	[1]	87,292		68,062
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		150		164
Restricted cash		59		100
Customer		371		219
Other		48		43
Mark-to-market derivative assets		31		140
Materials and supplies		199		181
Other current assets		50		35
Total current assets		908		882
Property, plant and equipment, net		5,415		5,160
Nuclear decommissioning trust funds		2,185		2,036
Goodwill		47		47
Mark-to-market derivative assets		23		53
Other noncurrent assets		315		90
Deferred Costs and Other Assets		7,985		7,386
Total assets (a)		8,893		8,268
Long-term debt due within one year		181		111
Accounts payable		269		216
Accrued expenses		119		115
Mark-to-market derivative liabilities		60		5
Energy Marketing Contract Liabilities, Current		15		12
Other current liabilities		30		13
Total current liabilities		674		472
Long-term debt		641		666
Asset retirement obligations		1,904		1,999
Pension obligations		9		9
Energy Marketing Contract Liabilities, Noncurrent		22		39
Other noncurrent liabilities		106		79
Deferred Credits and Other Liabilities, Noncurrent		2,682		2,792
Total liabilities		3,356		3,264
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		290		431	780	1,258
Restricted cash		158		123
Customer		2,433		2,095
Other		558		360
Mark-to-market derivative assets		917		1,365
Materials and supplies		935		880
Other current assets		701		535
Total current assets		6,528		6,342
Property, plant and equipment, net		25,585		25,843
Nuclear decommissioning trust funds		11,061		10,342
Goodwill		47		47	47
Mark-to-market derivative assets		476		733
Other noncurrent assets		688		627
Deferred Costs and Other Assets		14,861		14,344
Total assets (a)	[2]	46,974		46,529
Long-term debt due within one year		1,117		90
Accounts payable		1,610		1,583
Accrued expenses		989		935
Mark-to-market derivative liabilities		263		182
Energy Marketing Contract Liabilities, Current		72		100
Other current liabilities		313		356
Total current liabilities		5,683		4,933
Long-term debt		7,202		7,936
Asset retirement obligations		8,922		8,431
Energy Marketing Contract Liabilities, Noncurrent		80		117
Other noncurrent liabilities		595		602
Total liabilities	[2]	33,718		33,559
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		150		164
Restricted cash		27		77
Customer		371		219
Other		48		43
Mark-to-market derivative assets		31		140
Materials and supplies		199		181
Other current assets		44		30
Total current assets		870		854
Property, plant and equipment, net		5,415		5,160
Nuclear decommissioning trust funds		2,185		2,036
Goodwill		47		47
Mark-to-market derivative assets		23		53
Other noncurrent assets		277		85
Deferred Costs and Other Assets		7,947		7,381
Total assets (a)		8,817		8,235
Long-term debt due within one year		99		27
Accounts payable		269		216
Accrued expenses		116		113
Mark-to-market derivative liabilities		60		5
Energy Marketing Contract Liabilities, Current		15		12
Other current liabilities		30		13
Total current liabilities		589		386
Long-term debt		540		623
Asset retirement obligations		1,904		1,999
Pension obligations		9		9
Energy Marketing Contract Liabilities, Noncurrent		22		39
Other noncurrent liabilities		106		79
Deferred Credits and Other Liabilities, Noncurrent		2,581		2,749
Total liabilities		3,170		3,135
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		23		9	64	31
Restricted cash		24		24
Customer		395		300
Other		102		112
Materials and supplies		38		33
Other current assets		7		3
Total current assets		842		845
Property, plant and equipment, net		7,040		6,597
Other noncurrent assets		9		8
Deferred Costs and Other Assets		822		853
Total assets (a)	[3]	8,704		8,295
Long-term debt due within one year		41		378
Accounts payable		205		209
Accrued expenses		175		110
Other current liabilities		26		35
Total current liabilities		707		1,134
Long-term debt		2,281		1,480
Asset retirement obligations		21		17
Other noncurrent liabilities		61		61
Total liabilities	[3]	5,856		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		23		23
Customer		0		0
Other		0		0
Mark-to-market derivative assets		0		0
Materials and supplies		0		0
Other current assets		0		0
Total current assets		23		23
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
Deferred Costs and Other Assets		3		3
Total assets (a)		26		26
Long-term debt due within one year		41		79
Accounts payable		0		0
Accrued expenses		1		2
Mark-to-market derivative liabilities		0		0
Energy Marketing Contract Liabilities, Current		0		0
Other current liabilities		0		0
Total current liabilities		42		81
Long-term debt		0		41
Asset retirement obligations		0		0
Pension obligations		0		0
Energy Marketing Contract Liabilities, Noncurrent		0		0
Other noncurrent liabilities		0		0
Deferred Credits and Other Liabilities, Noncurrent		0		41
Total liabilities		42		122
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			$ 319	26	15	24
Restricted cash				14
Customer				581
Other				319
Mark-to-market derivative assets				18
Materials and supplies				122
Other current assets				80
Total current assets				1,474
Property, plant and equipment, net				10,864
Goodwill			1,406	1,406	1,407
Mark-to-market derivative assets				0
Other noncurrent assets				69
Deferred Costs and Other Assets				3,850
Total assets (a)	[4]			16,188
Long-term debt due within one year				456
Accounts payable				404
Accrued expenses				266
Mark-to-market derivative liabilities				0
Energy Marketing Contract Liabilities, Current				0
Other current liabilities				70
Total current liabilities				2,327
Long-term debt				4,823
Asset retirement obligations				8
Pension obligations				466
Energy Marketing Contract Liabilities, Noncurrent				0
Other noncurrent liabilities				200
Total liabilities	[4]			11,592
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		170	319
Restricted cash		43
Customer		496
Other		283
Mark-to-market derivative assets		0
Materials and supplies		116
Other current assets		71
Total current assets		1,838
Property, plant and equipment, net		11,598
Goodwill		4,005	$ 0
Other noncurrent assets		81
Deferred Costs and Other Assets		7,589
Total assets (a)	[4]	21,025
Long-term debt due within one year		253
Accounts payable		458
Accrued expenses		272
Energy Marketing Contract Liabilities, Current		335
Other current liabilities		47
Total current liabilities		2,284
Long-term debt		5,645
Asset retirement obligations		14
Pension obligations		0
Energy Marketing Contract Liabilities, Noncurrent		750
Other noncurrent liabilities		249
Total liabilities	[4]	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Restricted cash				12
Other current assets				0
Total current assets				12
Other noncurrent assets				18
Deferred Costs and Other Assets				18
Total assets (a)				30
Long-term debt due within one year				46
Accounts payable				0
Accrued expenses				2
Mark-to-market derivative liabilities				0
Energy Marketing Contract Liabilities, Current				0
Other current liabilities				0
Total current liabilities				48
Long-term debt				124
Asset retirement obligations				0
Pension obligations				0
Energy Marketing Contract Liabilities, Noncurrent				0
Other noncurrent liabilities				0
Deferred Credits and Other Liabilities, Noncurrent				124
Total liabilities				172
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Restricted cash		9
Other current assets		5
Total current assets		14
Other noncurrent assets		35
Deferred Costs and Other Assets		35
Total assets (a)		49
Long-term debt due within one year		40
Accounts payable		0
Accrued expenses		2
Mark-to-market derivative liabilities		0
Energy Marketing Contract Liabilities, Current		0
Other current liabilities		0
Total current liabilities		42
Long-term debt		101
Asset retirement obligations		0
Pension obligations		0
Energy Marketing Contract Liabilities, Noncurrent		0
Other noncurrent liabilities		0
Deferred Credits and Other Liabilities, Noncurrent		101
Total liabilities		143
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		101		3	$ 2	$ 3
Restricted cash		9		12
Customer		125		156
Other		44		242
Other current assets		2		12
Total current assets		399		546
Property, plant and equipment, net		2,521		2,322
Other noncurrent assets		44		19
Deferred Costs and Other Assets		537		519
Total assets (a)	[5]	3,457		3,387
Long-term debt due within one year		35		48
Accounts payable		132		96
Accrued expenses		38		70
Other current liabilities		8		14
Total current liabilities		320		297
Long-term debt		1,120		1,153
Other noncurrent liabilities		32		12
Total liabilities	[5]	2,423		2,387
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Restricted cash		9		12
Total current assets		9		12
Other noncurrent assets		23		18
Deferred Costs and Other Assets		23		18
Total assets (a)		32		30
Long-term debt due within one year		35		46
Accounts payable		0		0
Accrued expenses		2		2
Mark-to-market derivative liabilities		0		0
Energy Marketing Contract Liabilities, Current		0		0
Other current liabilities		0		0
Total current liabilities		37		48
Long-term debt		89		124
Asset retirement obligations		0		0
Pension obligations		0		0
Energy Marketing Contract Liabilities, Noncurrent		0		0
Other noncurrent liabilities		0		0
Deferred Credits and Other Liabilities, Noncurrent		89		124
Total liabilities		$ 126		$ 172

[1] Exelon’s consolidated assets include $8,893 million and $8,268 million at December 31, 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 $3,356 million and $3,264 million at December 31, 2016 and December 31, 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2–Variable Interest Entities.

[2] Generation’s consolidated assets include $8,817 million and $8,235 million at December 31, 2016 and 2015, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,170 million and $3,135 million at December 31, 2016 and 2015, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2–Variable Interest Entities.

[3] BGE’s consolidated assets include $26 million and $26 million at December 31, 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 $42 million and $122 million at December 31, 2016 and December 31, 2015, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 2 - Variable Interest Entities.

[4] PHI’s consolidated total assets include $49 million and $30 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $143 million and $172 million at December 31, 2016 and 2015, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 - Variable Interest Entities.

[5] ACE’s consolidated assets include $32 million and $30 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated liabilities include $126 million and $172 million at December 31, 2016 and 2015, respectively, of ACE’s consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 - Variable Interest Entities.