Nuclear Decommissioning (Tables)

6 Months Ended

Jun. 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		129
Costs incurred to decommission retired plants		(2)
Nuclear decommissioning ARO at June 30, 2013 (a)	$	4,868

Unrealized Gains (Losses) on nuclear decommissioning trust funds

		Exelon and Generation
			Three Months Ended				Six Months Ended
			June 30,				June 30,
			2013		2012		2013		2012
Net unrealized gains (losses) on decommissioning trust funds —
	Regulatory Agreement Units (a)	$	(102)	$	(96)	$	92	$	150
Net unrealized gains (losses) on decommissioning trust funds —
	Non-Regulatory Agreement Units (b)(c)		(40)		(35)		24		30

Zion Station pledged assets

	Exelon and Generation
	June 30,		December 31,
	2013		2012
Carrying value of Zion Station pledged assets	$	538	$	614
Payable to Zion Solutions (a)		491		564
Current portion of payable to Zion Solutions (b)		118		132
Withdrawals by Zion Solutions to pay decommissioning costs (c)		414		335

(a) 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.

(b) Included in Other current liabilities within Exelon's and Generation's Consolidated Balance Sheets.

(c) 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		129
Costs incurred to decommission retired plants		(2)
Nuclear decommissioning ARO at June 30, 2013 (a)	$	4,868

Unrealized Gains (Losses) on nuclear decommissioning trust funds

		Exelon and Generation
			Three Months Ended				Six Months Ended
			June 30,				June 30,
			2013		2012		2013		2012
Net unrealized gains (losses) on decommissioning trust funds —
	Regulatory Agreement Units (a)	$	(102)	$	(96)	$	92	$	150
Net unrealized gains (losses) on decommissioning trust funds —
	Non-Regulatory Agreement Units (b)(c)		(40)		(35)		24		30

Zion Station pledged assets

	Exelon and Generation
	June 30,		December 31,
	2013		2012
Carrying value of Zion Station pledged assets	$	538	$	614
Payable to Zion Solutions (a)		491		564
Current portion of payable to Zion Solutions (b)		118		132
Withdrawals by Zion Solutions to pay decommissioning costs (c)		414		335

(a) 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.

(b) Included in Other current liabilities within Exelon's and Generation's Consolidated Balance Sheets.

(c) Cumulative withdrawals since September 1, 2010.