Nuclear Decommissioning (Tables)

12 Months Ended

Dec. 31, 2012

Schedule Of Nuclear Decommissioning [Line Items]

Nuclear decommissioning asset retirement obligation rollforward

		Exelon and Generation
Nuclear decommissioning ARO at January 1, 2011	$	3,276
Accretion expense		209
Net increase due to changes in, and timing of, estimated future cash flows		198
Costs incurred to decommission retired plants		(3)
Nuclear decommissioning ARO at December 31, 2011 (a)		3,680
Accretion expense		231
Net increase due to changes in, and timing of, estimated future cash flows		833
Costs incurred to decommission retired plants		(3)
Nuclear decommissioning ARO at December 31, 2012 (a)	$	4,741

(a) Includes $10million and $5 million as the current portion of the ARO at December 31, 2012and 2011, respectively, which isincluded in other current liabilities on Exelon's and Generation's Consolidated Balance Sheets.

Unrealized Gains (Losses) on nuclear decommissioning trust funds

		Exelon and Generation
		For the Years Ended December 31,
		2012		2011		2010
Net unrealized gains (losses) on decommissioning
	trust funds — Regulatory Agreement Units (a) (b) (c)	$	386	$	(74)	$	294
Net unrealized gains (losses) on decommissioning
	trust funds — Non-Regulatory Agreement Units (c)		105		(4)		104

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(a)       Net unrealized gains (losses) related to Generation's NDT funds associated with Regulatory Agreement Units are included in regulatory liabilities on Exelon's Consolidated Balance Sheets and noncurrent payables to affiliates on Generation's Consolidated Balance Sheets.

(b)       Excludes$73million and $48 million of net unrealized gains (losses) related to the Zion Station pledged assets in 2012 and 2011. Net unrealized gains (losses) related to Zion Station pledged assets are included inthe payable for Zion Station decommissioning on Exelon's and Generation's Consolidated Balance Sheets.

(c)       Net unrealized gains (losses) related to Generation's NDT funds are included within other, net in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income.