Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Mar. 23, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 536	$ 635	$ 1,647		$ 6,502
Restricted cash		252	253
Accounts receivable, net
Customer		3,825	4,158
Other		958	1,201
Mark-to-market derivatives assets		833	917
Inventory
Materials and supplies		1,267	1,274
Other current assets		1,600	930
Total current assets		12,232	12,412
Property, plant and equipment, net		72,748	71,555
Nuclear decommissioning trust funds		12,641	11,061
Goodwill		6,677	6,677
Mark-to-market derivative assets		464	492
Other noncurrent assets		1,265	1,472
Total Deferred Debits And Other Assets		32,124	30,937
Total assets		117,104	114,904
Long-term debt due within one year		3,619	2,430
Accounts payable		3,134	3,441
Accrued expenses		2,878	3,460
Mark-to-market derivative liabilities (current liabilities)		244	282
Unamortized energy contract liabilities		340	407
Other		977	981
Total current liabilities		13,965	13,457
Long-term debt		30,315	31,575
Asset retirement obligations		9,848	9,111
Pension obligation(c)		4,082	4,248
Unamortized energy contract liabilities		705	830
Other noncurrent liabilities		1,828	1,827
Total liabilities	[1]	87,814	87,292
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	[2],[3]	68	150
Restricted cash	[2],[3]	55	59
Accounts receivable, net
Customer	[2],[3]	106	371
Other	[2],[3]	24	48
Mark-to-market derivatives assets	[2],[3]	0	31
Inventory
Materials and supplies	[2],[3]	193	199
Other current assets	[2],[3]	38	50
Total current assets	[2],[3]	484	908
Property, plant and equipment, net	[2],[3]	5,293	5,415
Nuclear decommissioning trust funds	[2],[3]	2,341	2,185
Goodwill	[2],[3]	0	47
Mark-to-market derivative assets	[2],[3]	0	23
Other noncurrent assets	[2],[3]	267	315
Total noncurrent assets	[2],[3]	7,901	7,985
Total assets	[2],[3]	8,385	8,893
Long-term debt due within one year	[2],[3]	191	181
Accounts payable	[2],[3]	80	269
Accrued expenses	[2],[3]	48	119
Mark-to-market derivative liabilities (current liabilities)	[2],[3]	0	60
Unamortized energy contract liabilities	[2],[3]	16	15
Other	[2],[3]	5	30
Total current liabilities	[2],[3]	340	674
Long-term debt	[2],[3]	616	641
Asset retirement obligations	[2],[3]	1,954	1,904
Pension obligation(c)	[2],[3],[4]	0	9
Unamortized energy contract liabilities	[2],[3]	13	22
Other noncurrent liabilities	[2],[3]	98	106
Total noncurrent liabilities	[2],[3]	2,681	2,682
Total liabilities	[2],[3]	3,021	3,356
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		265	290	373		431
Restricted cash		166	158
Accounts receivable, net
Customer		2,242	2,433
Other		447	558
Mark-to-market derivatives assets		833	917
Inventory
Materials and supplies		901	935
Other current assets		1,241	701
Total current assets		6,594	6,528
Property, plant and equipment, net		25,261	25,585
Nuclear decommissioning trust funds		12,641	11,061
Goodwill		47	47
Mark-to-market derivative assets		453	476
Other noncurrent assets		620	688
Total Deferred Debits And Other Assets		16,275	14,861
Total assets		48,130	46,974
Long-term debt due within one year		1,828	1,117
Accounts payable		1,527	1,610
Accrued expenses		722	989
Mark-to-market derivative liabilities (current liabilities)		225	263
Unamortized energy contract liabilities		61	72
Other		294	313
Total current liabilities		6,064	5,683
Long-term debt		7,010	7,202
Asset retirement obligations		9,655	8,922
Unamortized energy contract liabilities		67	80
Other noncurrent liabilities		598	595
Total liabilities	[5]	35,000	33,718
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		68	150
Restricted cash		48	27
Accounts receivable, net
Customer		106	371
Other		24	48
Mark-to-market derivatives assets		0	31
Inventory
Materials and supplies		193	199
Other current assets		34	44
Total current assets		473	870
Property, plant and equipment, net		5,293	5,415
Nuclear decommissioning trust funds		2,341	2,185
Goodwill		0	47
Mark-to-market derivative assets		0	23
Other noncurrent assets		235	277
Total noncurrent assets		7,869	7,947
Total assets		8,342	8,817
Long-term debt due within one year		154	99
Accounts payable		80	269
Accrued expenses		47	116
Mark-to-market derivative liabilities (current liabilities)		0	60
Unamortized energy contract liabilities		16	15
Other		5	30
Total current liabilities		302	589
Long-term debt		533	540
Asset retirement obligations		1,954	1,904
Pension obligation(c)	[4]	0	9
Unamortized energy contract liabilities		13	22
Other noncurrent liabilities		98	106
Total noncurrent liabilities		2,598	2,581
Total liabilities		2,900	3,170
Baltimore Gas and Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		12	23	5		9
Restricted cash		6	24
Accounts receivable, net
Customer		312	395
Other		75	102
Inventory
Materials and supplies		42	38
Other current assets		4	7
Total current assets		680	842
Property, plant and equipment, net		7,283	7,040
Other noncurrent assets		5	9
Total Deferred Debits And Other Assets		823	822
Total assets	[6]	8,786	8,704
Long-term debt due within one year		0	41
Accounts payable		205	205
Accrued expenses		100	175
Other		21	26
Total current liabilities		640	707
Long-term debt		2,282	2,281
Asset retirement obligations		22	21
Other noncurrent liabilities		59	61
Total liabilities	[6]	5,868	5,856
Baltimore Gas and Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents			0
Restricted cash			23
Accounts receivable, net
Customer			0
Other			0
Mark-to-market derivatives assets			0
Inventory
Materials and supplies			0
Other current assets			0
Total current assets			23
Property, plant and equipment, net			0
Nuclear decommissioning trust funds			0
Goodwill			0
Mark-to-market derivative assets			0
Other noncurrent assets			3
Total noncurrent assets			3
Total assets			26
Long-term debt due within one year			41
Accounts payable			0
Accrued expenses			1
Mark-to-market derivative liabilities (current liabilities)			0
Unamortized energy contract liabilities			0
Other			0
Total current liabilities			42
Long-term debt			0
Asset retirement obligations			0
Pension obligation(c)	[4]		0
Unamortized energy contract liabilities			0
Other noncurrent liabilities			0
Total noncurrent liabilities			0
Total liabilities			42
Pepco Holdings LLC [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		151	170	294	$ 319
Restricted cash		40	43
Accounts receivable, net
Customer		484	496
Other		199	283
Mark-to-market derivatives assets		0	0
Inventory
Materials and supplies		134	116
Other current assets		86	71
Total current assets		1,706	1,838
Property, plant and equipment, net		12,014	11,598
Goodwill		4,005	4,005
Mark-to-market derivative assets		0	0
Other noncurrent assets		79	81
Total Deferred Debits And Other Assets		7,470	7,589
Total assets	[7]	21,190	21,025
Long-term debt due within one year		160	253
Accounts payable		415	458
Accrued expenses		259	272
Mark-to-market derivative liabilities (current liabilities)		0	0
Unamortized energy contract liabilities		279	335
Other		36	47
Total current liabilities		1,562	2,284
Long-term debt		5,792	5,645
Asset retirement obligations		14	14
Unamortized energy contract liabilities		638	750
Other noncurrent liabilities		213	249
Total liabilities		12,349	13,009
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] | Successor [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents	[2]	0	0
Restricted cash	[2]	7	9
Accounts receivable, net
Customer	[2]	0	0
Other	[2]	0	0
Mark-to-market derivatives assets	[2]	0	0
Inventory
Materials and supplies	[2]	0	0
Other current assets	[2]	4	5
Total current assets	[2]	11	14
Property, plant and equipment, net	[2]	0	0
Nuclear decommissioning trust funds	[2]	0	0
Goodwill	[2]	0	0
Mark-to-market derivative assets	[2]	0	0
Other noncurrent assets	[2]	32	35
Total noncurrent assets	[2]	32	35
Total assets	[2]	43	49
Long-term debt due within one year	[2]	37	40
Accounts payable	[2]	0	0
Accrued expenses	[2]	1	2
Mark-to-market derivative liabilities (current liabilities)	[2]	0	0
Unamortized energy contract liabilities	[2]	0	0
Other	[2]	0	0
Total current liabilities	[2]	38	42
Long-term debt	[2]	83	101
Asset retirement obligations	[2]	0	0
Pension obligation(c)	[2],[4]	0	0
Unamortized energy contract liabilities	[2]	0	0
Other noncurrent liabilities	[2]	0	0
Total noncurrent liabilities	[2]	83	101
Total liabilities	[2]	121	143
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		7	101	$ 151		$ 3
Restricted cash		7	9
Accounts receivable, net
Customer		103	125
Other		46	44
Inventory
Materials and supplies		25	22
Other current assets		4	2
Total current assets		318	399
Property, plant and equipment, net		2,628	2,521
Other noncurrent assets		43	44
Total Deferred Debits And Other Assets		532	537
Total assets	[8]	3,478	3,457
Long-term debt due within one year		33	35
Accounts payable		122	132
Accrued expenses		56	38
Other		8	8
Total current liabilities		356	320
Long-term debt		1,105	1,120
Other noncurrent liabilities		23	32
Total liabilities		2,430	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
Mark-to-market derivatives assets		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
Mark-to-market derivative assets		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
Unamortized energy contract liabilities		0	0
Other		0	0
Total current liabilities		34	37
Long-term debt		74	89
Asset retirement obligations		0	0
Pension obligation(c)	[4]	0	0
Unamortized energy contract liabilities		0	0
Other noncurrent liabilities		0	0
Total noncurrent liabilities		74	89
Total liabilities		$ 108	$ 126

[1] Exelon’s consolidated assets include $8,385 million and $8,893 million at June 30, 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 $3,021 million and $3,356 million at June 30, 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 certain purchase accounting adjustments not pushed down to the ACE standalone entity.

[3] Includes certain purchase accounting adjustments not pushed down to the BGE standalone entity.

[4] 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.

[5] Generation’s consolidated assets include $8,342 million and $8,817 million at June 30, 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 $2,900 million and $3,170 million at June 30, 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.

[6] BGE’s consolidated assets include $26 million at December 31, 2016 of BGE’s consolidated VIE that can only be used to settle the liabilities of the VIE. BGE’s consolidated liabilities include $42 million at December 31, 2016 of BGE’s consolidated VIE for which the VIE creditors do not have recourse to BGE. BGE has no interests in any VIEs as of June 30, 2017. See Note 3 - Variable Interest Entities.

[7] PHI’s consolidated total assets include $43 million and $49 million at June 30, 2017 and December 31, 2016, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $121 million and $143 million at June 30, 2017 and December 31, 2016, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 3 - Variable Interest Entities.

[8] ACE’s consolidated total assets include $30 million and $32 million at June 30, 2017 and December 31, 2016, respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $108 million and $126 million at June 30, 2017 and December 31, 2016, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 3 - Variable Interest Entities.