Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Mar. 31, 2017	Dec. 31, 2016		Mar. 31, 2016	Mar. 23, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 609	$ 635		$ 960		$ 6,502
Restricted cash		254	253
Accounts receivable, net
Customer		3,886	4,158
Other		1,133	1,201
Derivative Asset, Current		847	917
Inventory
Materials and supplies		1,312	1,274
Other current assets		1,221	930
Total current assets		12,194	12,412
Property, plant and equipment, net		72,630	71,555
Nuclear decommissioning trust funds		12,362	11,061
Goodwill		6,677	6,677
Derivative Asset, Noncurrent		539	492
Other noncurrent assets		1,440	1,472
Total assets		117,068	114,904
Short-term borrowings		2,048	1,267
Long-term debt due within one year		3,645	2,430
Accounts payable		3,011	3,441
Accrued expenses		3,007	3,460
Mark-to-market derivative liabilities (current liabilities)		228	282
Other current liabilities		388	407
Other		942	981
Total current liabilities		14,437	13,457
Long-term debt		31,044	31,575
Asset retirement obligations		9,634	9,111
Pension obligation(c)		4,082	4,248
Energy Marketing Contract Liabilities, Noncurrent		779	830
Other noncurrent liabilities		1,853	1,827
Total liabilities	[1]	88,777	87,292
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		199	150
Restricted cash		124	59
Accounts receivable, net
Customer		347	371
Other		23	48
Derivative Asset, Current		41	31
Inventory
Materials and supplies		191	199
Other current assets		58	50
Total current assets		983	908
Property, plant and equipment, net		5,425	5,415
Nuclear decommissioning trust funds		2,286	2,185
Goodwill		47	47
Derivative Asset, Noncurrent		57	23
Other noncurrent assets		350	315
Total noncurrent assets		8,165	7,985
Total assets		9,148	8,893
Long-term debt due within one year		237	181
Accounts payable		275	269
Accrued expenses		85	119
Mark-to-market derivative liabilities (current liabilities)		18	60
Other current liabilities		16	15
Other		11	30
Total current liabilities		642	674
Long-term debt		626	641
Asset retirement obligations	[2]	1,929	1,904
Pension obligation(c)		8	9
Energy Marketing Contract Liabilities, Noncurrent		18	22
Other noncurrent liabilities		122	106
Total deferred credits and other liabilities		2,703	2,682
Total liabilities		3,345	3,356
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		400	290		377		431
Restricted cash		140	158
Accounts receivable, net
Customer		2,278	2,433
Other		545	558
Derivative Asset, Current		847	917
Inventory
Materials and supplies		957	935
Other current assets		881	701
Total current assets		6,514	6,528
Property, plant and equipment, net		25,893	25,585
Nuclear decommissioning trust funds		12,362	11,061
Goodwill		47	47
Derivative Asset, Noncurrent		527	476
Other noncurrent assets		648	688
Total assets		48,609	46,974
Short-term borrowings		717	699
Long-term debt due within one year		1,156	1,117
Accounts payable		1,482	1,610
Accrued expenses		720	989
Mark-to-market derivative liabilities (current liabilities)		209	263
Other current liabilities		68	72
Other		286	313
Total current liabilities		5,237	5,683
Long-term debt		7,904	7,202
Asset retirement obligations		9,444	8,922
Energy Marketing Contract Liabilities, Noncurrent		78	80
Other noncurrent liabilities		615	595
Total liabilities	[3]	35,045	33,718
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		199	150
Restricted cash		75	27
Accounts receivable, net
Customer		347	371
Other		23	48
Derivative Asset, Current		41	31
Inventory
Materials and supplies		191	199
Other current assets		54	44
Total current assets		930	870
Property, plant and equipment, net		5,425	5,415
Nuclear decommissioning trust funds		2,286	2,185
Goodwill		47	47
Derivative Asset, Noncurrent		57	23
Other noncurrent assets		314	277
Total noncurrent assets		8,129	7,947
Total assets		9,059	8,817
Long-term debt due within one year		159	99
Accounts payable		275	269
Accrued expenses		83	116
Mark-to-market derivative liabilities (current liabilities)		18	60
Other current liabilities		16	15
Other		11	30
Total current liabilities		562	589
Long-term debt		535	540
Asset retirement obligations		1,929	1,904	[2]
Pension obligation(c)		8	9
Energy Marketing Contract Liabilities, Noncurrent		18	22
Other noncurrent liabilities		122	106
Total deferred credits and other liabilities		2,612	2,581
Total liabilities		3,174	3,170
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		11	23		5		9
Restricted cash		43	24
Accounts receivable, net
Customer		393	395
Other		79	102
Inventory
Materials and supplies		41	38
Other current assets		11	7
Total current assets		812	842
Property, plant and equipment, net		7,166	7,040
Other noncurrent assets		10	9
Total assets	[4]	8,821	8,704
Short-term borrowings		95	45
Long-term debt due within one year		41	41
Accounts payable		186	205
Accrued expenses		120	175
Other		23	26
Total current liabilities		693	707
Long-term debt		2,282	2,281
Asset retirement obligations		20	21
Other noncurrent liabilities		59	61
Total liabilities	[4]	5,897	5,856
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		42	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		42	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		45	26
Long-term debt due within one year		41	41
Accounts payable		0	0
Accrued expenses		1	1
Mark-to-market derivative liabilities (current liabilities)		0	0
Other current liabilities		0	0
Other		0	0
Total current liabilities		42	42
Long-term debt			0
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	0
Total liabilities		42	42
Pepco Holdings LLC [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents						$ 319	26
Accounts receivable, net
Derivative Asset, Current			0
Inventory
Derivative Asset, Noncurrent			0
Mark-to-market derivative liabilities (current liabilities)			0
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		109	170		151	$ 319
Restricted cash		41	43
Accounts receivable, net
Customer		440	496
Other		210	283
Derivative Asset, Current		0
Inventory
Materials and supplies		131	116
Other current assets		64	71
Total current assets		1,650	1,838
Property, plant and equipment, net		11,801	11,598
Goodwill		4,005	4,005
Derivative Asset, Noncurrent		0
Other noncurrent assets		80	81
Total assets		21,018	21,025
Short-term borrowings		167	522
Long-term debt due within one year		241	253
Accounts payable		386	458
Accrued expenses		269	272
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		320	335
Other		43	47
Total current liabilities		1,800	2,284
Long-term debt		5,619	5,645
Asset retirement obligations		14	14
Energy Marketing Contract Liabilities, Noncurrent		701	750
Other noncurrent liabilities		225	249
Total liabilities		12,431	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Predecessor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			0
Restricted cash			9
Accounts receivable, net
Customer			0
Other			0
Derivative Asset, Current			0
Inventory
Materials and supplies			0
Other current assets			5
Total current assets			14
Property, plant and equipment, net			0
Nuclear decommissioning trust funds			0
Goodwill			0
Derivative Asset, Noncurrent			0
Other noncurrent assets			35
Total noncurrent assets			35
Total assets			49
Long-term debt due within one year			40
Accounts payable			0
Accrued expenses			2
Mark-to-market derivative liabilities (current liabilities)			0
Other current liabilities			0
Other			0
Total current liabilities			42
Long-term debt			101
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			101
Total liabilities			143
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0
Restricted cash		7
Accounts receivable, net
Customer		0
Other		0
Derivative Asset, Current		0
Inventory
Materials and supplies		0
Other current assets		4
Total current assets		11
Property, plant and equipment, net		0
Nuclear decommissioning trust funds		0
Goodwill		0
Derivative Asset, Noncurrent		0
Other noncurrent assets		33
Total noncurrent assets		33
Total assets		44
Long-term debt due within one year		37
Accounts payable		0
Accrued expenses		1
Mark-to-market derivative liabilities (current liabilities)		0
Other current liabilities		0
Other		0
Total current liabilities		38
Long-term debt		91
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		91
Total liabilities		129
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		54	101		$ 122		$ 3
Restricted cash		7	9
Accounts receivable, net
Customer		111	125
Other		41	44
Inventory
Materials and supplies		23	22
Other current assets		3	2
Total current assets		333	399
Property, plant and equipment, net		2,583	2,521
Other noncurrent assets		42	44
Total assets		3,451	3,457
Long-term debt due within one year		33	35
Accounts payable		125	132
Accrued expenses		50	38
Other		9	8
Total current liabilities		320	320
Long-term debt		1,112	1,120
Other noncurrent liabilities		23	32
Total liabilities		2,399	2,423
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash		7	9
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		7	9
Property, plant and equipment, net		0	0
Nuclear decommissioning trust funds		0	0
Goodwill		0	0
Derivative Asset, Noncurrent		0	0
Other noncurrent assets		23	23
Total noncurrent assets		23	23
Total assets		30	32
Long-term debt due within one year		33	35
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		34	37
Long-term debt		81	89
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		81	89
Total liabilities		$ 115	$ 126

[1] Exelon’s consolidated assets include $9,148 million and $8,893 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,345 million and $3,356 million at March 31, 2017 and December 31, 2016, 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 Consolidated Balance Sheets. See Note 13 - Retirement Benefits for additional details.

[3] Generation’s consolidated assets include $9,059 million and $8,817 million at March 31, 2017 and December 31, 2016, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,174 million and $3,170 million at March 31, 2017 and December 31, 2016, 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 $45 million and $26 million at March 31, 2017 and December 31, 2016, 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 $42 million at March 31, 2017 and December 31, 2016, respectively, of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. See Note 3 - Variable Interest Entities.