Asset Retirement Obligations - Pledged Assets and Payables to ZionSolutions (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		$ 113	$ 206
Decommissioning Liability, Noncurrent		14	90
Asset Retirement Obligations, Noncurrent		9,111	8,585
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		113	206
Decommissioning Liability, Noncurrent		14	90
Asset Retirement Obligation, Current		10	7
Asset Retirement Obligations, Noncurrent		8,922	8,431
Decommissioning Funds Withdrawal	[1]	878	786
Exelon Generation Co L L C [Member] | Nuclear Decommissioning Asset Retirement Obligation [Member]
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		113	206
Payable to Zion Solutions	[2]	104	189
Asset Retirement Obligation, Current	[3]	$ 90	$ 99

[1] (c)Includes project expenses to decommission Zion Station and estimated tax payments on Zion Station NDT fund earnings.

[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] Included in Other current liabilities within Exelon’s and Generation’s Consolidated Balance Sheets.