Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Jun. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Total assets	[1]	$ 126,313	$ 124,977
Total liabilities	[1]	91,442	90,404
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets	[2]	47,003	48,995
Total liabilities	[2]	31,776	33,165
Exelon Generation Co L L C [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,122	1,079
Total liabilities		399	260
Exelon's ownership interest in VIE		168	191
Other ownership interests in VIE		555	629
Variable Interest Entity, Not Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets		1,122	1,079
Total liabilities		399	260
Exelon's ownership interest in VIE		168	191
Other ownership interests in VIE		555	629
Equity Investment VIE [Member] | Exelon Generation Co L L C [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement VIE [Member] | Exelon Generation Co L L C [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		705	636
Total liabilities		172	33
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		533	604
Commercial Agreement VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets		705	636
Total liabilities		172	33
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		533	604
Equity Investment VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		417	443
Total liabilities		227	227
Exelon's ownership interest in VIE		168	191
Other ownership interests in VIE		22	25
Equity Investment VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets		417	443
Total liabilities		227	227
Exelon's ownership interest in VIE		168	191
Other ownership interests in VIE		$ 22	$ 25

[1] Exelon’s consolidated assets include $9,937 million and $9,532 million at June 30, 2020 and December 31, 2019, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,542 million and $3,473 million at June 30, 2020 and December 31, 2019, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 16 — Variable Interest Entities for additional information.

[2] Generation’s consolidated assets include $9,916 million and $9,512 million at June 30, 2020 and December 31, 2019, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,505 million and $3,429 million at June 30, 2020 and December 31, 2019, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 16 — Variable Interest Entities for additional information.