Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Total assets	[1]	$ 427	$ 205
Total liabilities	[1]	147	52
Our ownership interest	[1]	11	9
Other ownership interests	[1]	269	144
Pledged assets for Zion Station decommissioning		206	319
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Pledged assets for Zion Station decommissioning		206	319
Payable To Thirdparty To Decommission Nuclear Plant Funded By Pledged Assets	[2]	189	292
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	263	114
Total liabilities	[1]	22	3
Our ownership interest	[1]	0	0
Other ownership interests	[1]	241	111
Commercial Agreement Variable Interest Entities [Member] | Scenario, Adjustment [Member]
Variable Interest Entity [Line Items]
Total assets			392
Total liabilities			234
Other ownership interests			158
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets	[1]	164	91
Total liabilities	[1]	125	49
Our ownership interest	[1]	11	9
Other ownership interests	[1]	28	33
Investments [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		21	13
Investments [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Investments [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		21	13
Contract Intangible Asset [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		9	9
Contract Intangible Asset [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		9	9
Contract Intangible Asset [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Payment Guarantee [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		3	3
Payment Guarantee [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Payment Guarantee [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		3	3
Asset Held In Trust Noncurrent [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss	[3]	17	27
Asset Held In Trust Noncurrent [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss	[3]	17	27
Asset Held In Trust Noncurrent [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss	[3]	$ 0	$ 0

[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] 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.

[3] 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 $206 million and $319 million as of December 31, 2015 and December 31, 2014, respectively; offset by payables to ZionSolutions LLC of $189 million and $292 million as of December 31, 2015 and December 31, 2014, respectively. These items are included to provide information regarding the relative size of the ZionSolutions LLC unconsolidated VIE.