Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Sep. 30, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Total assets	[1]	$ 1,117	$ 427
Total liabilities	[1]	489	147
Exelon's ownership interest in VIE	[1]	193	11
Other ownership interests in VIE	[1]	439	269
Assets Held-in-trust, Noncurrent		135	206
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	586	263
Total liabilities	[1]	181	22
Exelon's ownership interest in VIE	[1]	0	0
Other ownership interests in VIE	[1]	405	241
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	531	164
Total liabilities	[1]	308	125
Exelon's ownership interest in VIE	[1]	193	11
Other ownership interests in VIE	[1]	34	28
Investments [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		225
Investments [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss			21
Investments [Member] | Maximum [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0	0
Investments [Member] | Maximum [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		225	21
Contract Intangible Asset [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Contract Intangible Asset [Member] | Maximum [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		9	9
Contract Intangible Asset [Member] | Maximum [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0
Payment Guarantee [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		3
Payment Guarantee [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss			3
Payment Guarantee [Member] | Maximum [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		0
Payment Guarantee [Member] | Maximum [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		3	3
Asset Held In Trust Noncurrent [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	11	17
Asset Held In Trust Noncurrent [Member] | Maximum [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	11	17
Asset Held In Trust Noncurrent [Member] | Maximum [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss	[2]	0
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Assets Held-in-trust, Noncurrent		135	206
Payable to Zion Solutions	[3]	124	$ 189
Exelon Generation Co L L C [Member] | Investments [Member] | Maximum [Member]
Variable Interest Entity [Line Items]
Registrants' maximum exposure to loss		$ 20

[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 $135 million and $206 million as of September 30, 2016 and December 31, 2015, respectively; offset by payables to ZionSolutions LLC of $124 million and $189 million as of September 30, 2016 and December 31, 2015, 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.