Property, Plant and Equipment (Tables)

12 Months Ended

Dec. 31, 2012

Property, Plant and Equipment [Abstract]

Schedule of Property, Plant and Equipment

Property, plant and equipment consisted of the following:

	EME				Midwest Generation
	December 31,				December 31,
(in millions)	2012		2011		2012		2011
Land	$	36	$	36	$	32	$	32
Power plant facilities	4,612		4,560		$	1,293	$	1,309
Leasehold improvements	4		4		—		—
Emission allowances	672		672		639		639
Construction in progress1	495		366		28		8
Equipment, furniture and fixtures	128		129		13		15
Plant and equipment under lease financing	—		—		1,333		1,334
	5,947		5,767		3,338		3,337
Less accumulated depreciation and amortization	1,431		1,295		1,260		1,152
Net property, plant and equipment	$	4,516	$	4,472	$	2,078	$	2,185

¹  Included $466 million and $357 million at December 31, 2012 and 2011, respectively, for EME's new gas and wind projects under construction.

Schedule of Changes in ARO Liability

A reconciliation of the changes in Midwest Generation's ARO liability is as follows:

	Years Ended December 31,
(in millions)	2012		2011			2010
Beginning balance	$	2	$	2		$	2
Accretion expense	—		1			—
Revisions	—		(1		)	—
Ending balance	$	2	$	2		$	2

A reconciliation of the changes in EME's ARO liability is as follows:

	Years Ended December 31,
(in millions)	2012		2011			2010
Beginning balance	$	70	$	47		$	38
Accretion expense	5		5			2
Revisions	—		(1		)	—
Liabilities added	5		19			8
Transfers out1	—		—			(1		)
Ending balance	$	80	$	70		$	47

¹  Transfers out represents the deconsolidation of two wind projects and consolidation of one coal project effective January 1, 2010.