Asset Retirement Obligations - Pledged Assets and Payables to ZionSolutions (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		$ 206	$ 319
Exelon Generation Co L L C [Member]
Asset Retirement Obligations [Line Items]
Carrying value of Zion Station pledged assets		206	319
Payable to Zion Solutions	[1]	189	292
Current portion of payable to Zion Solutions	[2]	99	137
Withdrawals by Zion Solutions to pay decommissioning costs	[3]	$ 786	$ 666

[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.

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

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