Nuclear Decommissioning (Tables)

9 Months Ended

Sep. 30, 2013

Schedule Of Nuclear Decommissioning [Line Items]

Nuclear decommissioning asset retirement obligation rollforward

Nuclear decommissioning ARO at December 31, 2012 (a)	$	4,741
Accretion expense		194
Net decrease due to changes in, and timing of, estimated cash flows		(141)
Costs incurred to decommission retired plants		(2)
Nuclear decommissioning ARO at September 30, 2013 (a)	$	4,792

Unrealized Gains (Losses) on nuclear decommissioning trust funds

		Exelon and Generation
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
			2013		2012		2013		2012
Net unrealized gains on decommissioning trust funds —
	Regulatory Agreement Units (a)	$	103	$	202	$	196	$	352
Net unrealized gains on decommissioning trust funds —
	Non-Regulatory Agreement Units (b)(c)		46		71		70		101

Zion Station pledged assets

	Exelon and Generation
	September 30,		December 31,
	2013		2012
Carrying value of Zion Station pledged assets	$	486	$	614
Payable to Zion Solutions (a)		443		564
Current portion of payable to Zion Solutions (b)		104		132
Withdrawals by Zion Solutions to pay decommissioning costs (c)		458		335

• 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.
• Included in Other current liabilities within Exelon's and Generation's Consolidated Balance Sheets.
• Cumulative withdrawals since September 1, 2010.

Exelon Generation Co L L C [Member]

Schedule Of Nuclear Decommissioning [Line Items]

Nuclear decommissioning asset retirement obligation rollforward

Nuclear decommissioning ARO at December 31, 2012 (a)	$	4,741
Accretion expense		194
Net decrease due to changes in, and timing of, estimated cash flows		(141)
Costs incurred to decommission retired plants		(2)
Nuclear decommissioning ARO at September 30, 2013 (a)	$	4,792

Unrealized Gains (Losses) on nuclear decommissioning trust funds

		Exelon and Generation
			Three Months Ended				Nine Months Ended
			September 30,				September 30,
			2013		2012		2013		2012
Net unrealized gains on decommissioning trust funds —
	Regulatory Agreement Units (a)	$	103	$	202	$	196	$	352
Net unrealized gains on decommissioning trust funds —
	Non-Regulatory Agreement Units (b)(c)		46		71		70		101

Zion Station pledged assets

	Exelon and Generation
	September 30,		December 31,
	2013		2012
Carrying value of Zion Station pledged assets	$	486	$	614
Payable to Zion Solutions (a)		443		564
Current portion of payable to Zion Solutions (b)		104		132
Withdrawals by Zion Solutions to pay decommissioning costs (c)		458		335

• 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.
• Included in Other current liabilities within Exelon's and Generation's Consolidated Balance Sheets.
• Cumulative withdrawals since September 1, 2010.