Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Jun. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total assets	[1]	$ 1,170	$ 1,205
Total liabilities	[1]	293	502
Exelon's ownership interest in VIE	[1]	268	248
Other ownership interests in VIE	[1]	609	455
Registrants' maximum exposure to loss		16
Pledged assets for Zion Station decommissioning		75	113
Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		268	264
Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	6	9
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	641	638
Total liabilities	[1]	64	215
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	577	423
Commercial Agreement Variable Interest Entities [Member] | Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Commercial Agreement Variable Interest Entities [Member] | Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	6	9
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	529	567
Total liabilities	[1]	229	287
Exelon's ownership interest in VIE	[1]	268	248
Other ownership interests in VIE	[1]	32	32
Equity Investment VIE [Member] | Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		268	264
Equity Investment VIE [Member] | Finite-Lived Intangible Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Equity Investment VIE [Member] | Debt [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Equity Investment VIE [Member] | Other Assets [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	0	0
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Other ownership interests in VIE		16
Pledged assets for Zion Station decommissioning		75	113
Payable to Zion Solutions	[3]	$ 69	$ 104

[1] These items represent amounts on the unconsolidated VIE balance sheets, not on Exelon’s or Generation’s Consolidated Balance Sheets. These items are included to provide information regarding the relative size of the unconsolidated VIEs.

[2] These items represent amounts on Exelon’s and Generation’s Consolidated Balance Sheets related to the asset sale agreement with ZionSolutions, LLC. The net assets pledged for Zion Station decommissioning includes gross pledged assets of $75 million and $113 million as of June 30, 2017 and December 31, 2016, respectively; offset by payables to ZionSolutions LLC of $69 million and $104 million as of June 30, 2017 and December 31, 2016, respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE.

[3] Excludes a liability recorded within Exelon’s and Generation’s Consolidated Balance Sheets related to the tax obligation on the unrealized activity associated with the Zion Station NDT funds. The NDT funds will be utilized to satisfy the tax obligations as gains and losses are realized.