Variable Interest Entities - Summary of Significant Unconsolidated VIEs (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Variable Interest Entity [Line Items]
Total assets		$ 1,205	$ 427
Total liabilities		502	147
Our ownership interest		248	11
Other ownership interests		455	269
Our maximum exposure to loss		18
Pledged assets for Zion Station decommissioning		113	206
Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Our ownership interest		18
Pledged assets for Zion Station decommissioning		113	206
Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets		638	263
Total liabilities		215	22
Our ownership interest		0	0
Other ownership interests		423	241
Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Total assets		567	164
Total liabilities		287	125
Our ownership interest		248	11
Other ownership interests		32	28
Investments [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		264	21
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		264	21
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		9	17
Asset Held In Trust Noncurrent [Member] | Commercial Agreement Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		9	17
Asset Held In Trust Noncurrent [Member] | Equity Method Investment Variable Interest Entities [Member]
Variable Interest Entity [Line Items]
Our maximum exposure to loss		0	0
Nuclear Decommissioning Asset Retirement Obligation [Member] | Exelon Generation Co L L C [Member]
Variable Interest Entity [Line Items]
Pledged assets for Zion Station decommissioning		113	206
Asset Retirement Obligations, Noncurrent	[1]	$ 104	$ 189

[1] 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.