Asset Retirement Obligations (Tables)

6 Months Ended

Jun. 30, 2014

Asset Retirement Obligations Tables [Line Items]

Nuclear decommissioning asset retirement obligation rollforward

Nuclear decommissioning ARO at December 31, 2013 (a)	$	4,855
Consolidation of CENG (b)		1,701
Accretion expense		154
Costs incurred to decommission retired plants		(3)
Nuclear decommissioning ARO at June 30, 2014 (a)	$	6,707

(a)Includes $9 million as the current portion of the ARO at June 30, 2014 and December 31, 2013 which is included in Other current liabilities on Exelon's and Generation's Consolidated Balance Sheets.

(b)Includes the fair value of the CENG ARO liability as of April 1, 2014, the date of consolidation. See Note 6 - Investment in Constellation Energy Nuclear Group, LLC for additional information.

Unrealized Gains (Losses) on nuclear decommissioning trust funds

		Exelon and Generation
			Three Months Ended				Six Months Ended
			June 30,				June 30,
			2014		2013		2014		2013
Net unrealized gains (losses) on decommissioning trust funds —
	Regulatory Agreement Units (a)	$	172	$	(102)	$	234	$	92
Net unrealized gains (losses) on decommissioning trust funds —
	Non-Regulatory Agreement Units (b)(c)		128		(40)		141		24

(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 $ 10 million and $2 million of net unrealized gains related to the Zion Station pledged assets for the three months ended June 30, 2014 and 2013, respectively, and $20 million and $3 million of net unrealized gains related to the Zion Station pledged assets for the six months ended June 30, 2014 and 2013, respectively. Net unrealized gains (losses) related to Zion Station pledged assets are included in the 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 with Non-Regulatory Agreement Units are included within Other, net in Exelon's and Generation's Consolidated Statements of Operations and Comprehensive Income.

Zion Station pledged assets

	Exelon and Generation
	June 30,		December 31,
	2014		2013
Carrying value of Zion Station pledged assets	$	402	$	458
Payable to Zion Solutions (a)		357		414
Current portion of payable to Zion Solutions (b)		93		109
Withdrawals by Zion Solutions to pay decommissioning costs (c)		575		498

• 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]

Asset Retirement Obligations Tables [Line Items]

Nuclear decommissioning asset retirement obligation rollforward

Nuclear decommissioning ARO at December 31, 2013 (a)	$	4,855
Consolidation of CENG (b)		1,701
Accretion expense		154
Costs incurred to decommission retired plants		(3)
Nuclear decommissioning ARO at June 30, 2014 (a)	$	6,707

Unrealized Gains (Losses) on nuclear decommissioning trust funds

		Exelon and Generation
			Three Months Ended				Six Months Ended
			June 30,				June 30,
			2014		2013		2014		2013
Net unrealized gains (losses) on decommissioning trust funds —
	Regulatory Agreement Units (a)	$	172	$	(102)	$	234	$	92
Net unrealized gains (losses) on decommissioning trust funds —
	Non-Regulatory Agreement Units (b)(c)		128		(40)		141		24

Zion Station pledged assets

	Exelon and Generation
	June 30,		December 31,
	2014		2013
Carrying value of Zion Station pledged assets	$	402	$	458
Payable to Zion Solutions (a)		357		414
Current portion of payable to Zion Solutions (b)		93		109
Withdrawals by Zion Solutions to pay decommissioning costs (c)		575		498

• 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.