Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Jun. 30, 2021	Dec. 31, 2020
Variable Interest Entity [Line Items]
Total assets	[1]	$ 129,396	$ 129,317
Total liabilities	[1]	94,896	94,449
Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,164	1,178
Total liabilities		305	284
Exelon's ownership interest in VIE		149	157
Other ownership interests in VIE		710	737
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Total assets	[2]	45,821	48,094
Total liabilities	[2]	32,836	33,418
Exelon Generation Co L L C [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		1,164	1,178
Total liabilities		305	284
Exelon's ownership interest in VIE		149	157
Other ownership interests in VIE		710	737
Commercial Agreement VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		786	777
Total liabilities		95	61
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		691	716
Commercial Agreement VIE [Member] | Exelon Generation Co L L C [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		786	777
Total liabilities		95	61
Exelon's ownership interest in VIE		0	0
Other ownership interests in VIE		691	716
Equity Investment VIE [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		378	401
Total liabilities		210	223
Exelon's ownership interest in VIE		149	157
Other ownership interests in VIE		19	21
Equity Investment VIE [Member] | Exelon Generation Co L L C [Member] | Variable Interest Entity, Not Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Total assets		378	401
Total liabilities		210	223
Exelon's ownership interest in VIE		149	157
Other ownership interests in VIE		$ 19	$ 21

[1] Exelon’s consolidated assets include $10,093 million and $10,200 million at June 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Exelon’s consolidated liabilities include $3,578 million and $3,598 million at June 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Exelon. See Note 17 — Variable Interest Entities for additional information.

[2] Generation’s consolidated assets include $10,077 million and $10,182 million at June 30, 2021 and December 31, 2020, respectively, of certain VIEs that can only be used to settle the liabilities of the VIE. Generation’s consolidated liabilities include $3,563 million and $3,572 million at June 30, 2021 and December 31, 2020, respectively, of certain VIEs for which the VIE creditors do not have recourse to Generation. See Note 17 — Variable Interest Entities for additional information.