Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Total assets	[1]	$ 1,154	$ 1,205
Total liabilities	[1]	268	502
Exelon's ownership interest in VIE	[1]	259	248
Other ownership interests in VIE	[1]	627	455
Registrants' maximum exposure to loss		17
Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		259	264
Contract intangible asset
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Debt and payment guarantees
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Net assets pledged for Zion Station decommissioning(b)
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	4	9
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	635	638
Total liabilities	[1]	39	215
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	596	423
Commercial Agreement Variable Interest Entities [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Contract intangible asset
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Commercial Agreement Variable Interest Entities [Member] | Debt and payment guarantees
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Commercial Agreement Variable Interest Entities [Member] | Net assets pledged for Zion Station decommissioning(b)
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	4	9
Equity Investment VIE [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	519	567
Total liabilities	[1]	229	287
Exelon's ownership interest in VIE	[1]	259	248
Other ownership interests in VIE	[1]	31	32
Equity Investment VIE [Member] | Carrying amount of equity method investments
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		259	264
Equity Investment VIE [Member] | Contract intangible asset
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Equity Investment VIE [Member] | Debt and payment guarantees
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	3
Equity Investment VIE [Member] | Net assets pledged for Zion Station decommissioning(b)
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		17
Held-to-maturity Securities Pledged as Collateral		57	113
Accounts Payable, Interest-bearing, Noncurrent	[3]	$ 53	$ 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 $57 million and $113 million as of September 30, 2017 and December 31, 2016, respectively; offset by payables to ZionSolutions LLC of $53 million and $104 million as of September 30, 2017 and December 31, 2016, respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE. See Note 13 - Nuclear Decommissioning for additional details.

[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.