Variable Interest Entities - Assets and Liabilities of VIES which Creditors or Beneficiaries have no Recourse (Details) - USD ($) $ in Millions		Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Cash and cash equivalents		$ 735	$ 1,349	$ 694	$ 898
Restricted cash and cash equivalents		252	247	206	207
Accounts receivable, net
Customer		4,125	4,607
Other		1,008	1,256
Inventory, net
Materials and Supplies		1,412	1,351
Other current assets		1,218	1,238
Total current assets		11,655	13,360
Property, plant and equipment, net		78,030	76,707
NDT funds		12,513	11,661
Other Assets, Noncurrent		3,038	1,575
Total assets	[1]	121,596	119,666
Long-term debt due within one year		3,776	1,349
Accounts payable		3,248	3,800
Accrued expenses		1,706	2,112
Unamortized energy contract liabilities		145	149
Other Liabilities, Current		1,367	1,035
Total current liabilities		12,934	11,404
Long-term debt		31,909	34,075
Asset retirement obligations		10,023	9,679
Unamortized energy contract liabilities		398	463
Other Liabilities, Noncurrent		3,053	2,130
Total liabilities	[1]	87,689	86,596
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		106	414
Restricted cash and cash equivalents		75	66
Accounts receivable, net
Customer		161	146
Other		39	23
Inventory, net
Materials and Supplies		217	212
Other current assets		28	52
Total current assets		626	913
Property, plant and equipment, net		6,084	6,145
NDT funds		2,589	2,351
Other Assets, Noncurrent		227	258
Total noncurrent assets		8,900	8,754
Total assets		9,526	9,667
Long-term debt due within one year		560	87
Accounts payable		89	96
Accrued expenses		52	72
Unamortized energy contract liabilities		11	15
Other Liabilities, Current		3	3
Total current liabilities		715	273
Long-term debt		558	1,072
Asset retirement obligations		2,218	2,160
Unamortized energy contract liabilities		0	1
Other Liabilities, Noncurrent		77	42
Total noncurrent liabilities		2,853	3,275
Total liabilities		3,568	3,548
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		575	750	420	416
Restricted cash and cash equivalents		122	153	130	138
Accounts receivable, net
Customer		2,528	2,941
Other		326	562
Inventory, net
Materials and Supplies		984	963
Other current assets		849	883
Total current assets		7,376	8,433
Property, plant and equipment, net		23,810	23,981
NDT funds		12,513	11,661
Other Assets, Noncurrent		1,841	755
Total assets	[2]	48,402	47,556
Long-term debt due within one year		2,733	906
Accounts payable		1,517	1,847
Accrued expenses		767	898
Unamortized energy contract liabilities		26	31
Other Liabilities, Current		481	279
Total current liabilities		6,842	5,769
Long-term debt		5,079	6,989
Asset retirement obligations		9,792	9,450
Unamortized energy contract liabilities		13	20
Other Liabilities, Noncurrent		1,449	610
Total liabilities	[2]	32,810	32,048
Exelon Generation Co L L C [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		106	414
Restricted cash and cash equivalents		73	62
Accounts receivable, net
Customer		161	146
Other		39	23
Inventory, net
Materials and Supplies		217	212
Other current assets		27	49
Total current assets		623	906
Property, plant and equipment, net		6,084	6,145
NDT funds		2,589	2,351
Other Assets, Noncurrent		207	232
Total noncurrent assets		8,880	8,728
Total assets		9,503	9,634
Long-term debt due within one year		540	66
Accounts payable		89	96
Accrued expenses		51	72
Unamortized energy contract liabilities		11	15
Other Liabilities, Current		3	3
Total current liabilities		694	252
Long-term debt		524	1,025
Asset retirement obligations		2,218	2,160
Unamortized energy contract liabilities		0	1
Other Liabilities, Noncurrent		77	42
Total noncurrent liabilities		2,819	3,228
Total liabilities		3,513	3,480
Pepco Holdings LLC [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		54	124	195	30
Restricted cash and cash equivalents		37	43	38	42
Accounts receivable, net
Customer		489	453
Other		196	177
Inventory, net
Materials and Supplies		195	163
Other current assets		74	75
Total current assets		1,546	1,533
Property, plant and equipment, net		13,788	13,446
Other Assets, Noncurrent		360	60
Total assets	[3]	22,454	21,984
Long-term debt due within one year		118	125
Accounts payable		426	496
Accrued expenses		224	256
Unamortized energy contract liabilities		119	119
Other Liabilities, Current		133	123
Total current liabilities		1,328	1,592
Long-term debt		6,391	6,134
Asset retirement obligations		53	52
Unamortized energy contract liabilities		385	442
Other Liabilities, Noncurrent		617	369
Total liabilities	[3]	12,882	12,702
Pepco Holdings LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		2	4
Accounts receivable, net
Customer		0	0
Other		0	0
Inventory, net
Materials and Supplies		0	0
Other current assets		1	3
Total current assets		3	7
Property, plant and equipment, net		0	0
NDT funds		0	0
Other Assets, Noncurrent		20	26
Total noncurrent assets		20	26
Total assets		23	33
Long-term debt due within one year		20	21
Accounts payable		0	0
Accrued expenses		1	1
Unamortized energy contract liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		21	22
Long-term debt		34	47
Asset retirement obligations		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Noncurrent		0	0
Total noncurrent liabilities		34	47
Total liabilities		55	69
Atlantic City Electric Company [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		4	7	6	2
Restricted cash and cash equivalents		2	4	$ 5	$ 6
Accounts receivable, net
Customer		112	95
Other		50	55
Inventory, net
Other current assets		7	5
Total current assets		299	240
Property, plant and equipment, net		3,093	2,966
Other Assets, Noncurrent		60	40
Total assets	[4]	3,886	3,699
Long-term debt due within one year		19	18
Accounts payable		135	154
Accrued expenses		36	35
Other Liabilities, Current		10	4
Total current liabilities		299	422
Long-term debt		1,310	1,170
Other Liabilities, Noncurrent		44	27
Total liabilities	[4]	2,605	2,573
Atlantic City Electric Company [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents		0	0
Restricted cash and cash equivalents		2	4
Accounts receivable, net
Customer		0	0
Other		0	0
Inventory, net
Materials and Supplies		0	0
Other current assets		0	0
Total current assets		2	4
Property, plant and equipment, net		0	0
NDT funds		0	0
Other Assets, Noncurrent		17	19
Total noncurrent assets		17	19
Total assets		19	23
Long-term debt due within one year		19	18
Accounts payable		0	0
Accrued expenses		1	1
Unamortized energy contract liabilities		0	0
Other Liabilities, Current		0	0
Total current liabilities		20	19
Long-term debt		31	40
Asset retirement obligations		0	0
Unamortized energy contract liabilities		0	0
Other Liabilities, Noncurrent		0	0
Total noncurrent liabilities		31	40
Total liabilities		$ 51	$ 59

[1] Exelon’s consolidated assets include $9,526 million and $9,667 million at June 30, 2019 and December 31, 2018, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,568 million and $3,548 million at June 30, 2019 and December 31, 2018, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 2 — Variable Interest Entities for additional information.

[2] Generation’s consolidated assets include $9,503 million and $9,634 million at June 30, 2019 and December 31, 2018, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,513 million and $3,480 million at June 30, 2019 and December 31, 2018, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 2 — Variable Interest Entities for additional information.

[3] PHI’s consolidated total assets include $23 million and $33 million at June 30, 2019 and December 31, 2018, respectively, of PHI's consolidated VIE that can only be used to settle the liabilities of the VIE. PHI’s consolidated total liabilities include $55 million and $69 million at June 30, 2019 and December 31, 2018, respectively, of PHI's consolidated VIE for which the VIE creditors do not have recourse to PHI. See Note 2 — Variable Interest Entities for additional information.

[4] ACE’s consolidated total assets include $19 million and $23 million at June 30, 2019 and December 31, 2018, respectively, of ACE's consolidated VIE that can only be used to settle the liabilities of the VIE. ACE’s consolidated total liabilities include $51 million and $59 million at June 30, 2019 and December 31, 2018, respectively, of ACE's consolidated VIE for which the VIE creditors do not have recourse to ACE. See Note 2 — Variable Interest Entities for additional information.