Asset Retirement Obilgations Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2011

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Asset Retirement Obligations [Table Text Block]

AROs, which are included in Other noncurrent liabilities in the consolidated balance sheets, consist of the following (in millions):

	As of December 31,
	2011		2010
Trojan decommissioning activities	$	37	$	38
Utility plant	38		16
Non-utility property	12		10
Asset retirement obligations	$	87	$	64

Schedule of Change in Asset Retirement Obligation [Table Text Block]

The following is a summary of the changes in the Company’s AROs (in millions):

	Years Ended December 31,
	2011			2010			2009
Balance as of beginning of year	$	64		$	63		$	58
Liabilities incurred	1			1			—
Liabilities settled	(4		)	(3		)	(4		)
Accretion expense	4			4			4
Revisions in estimated cash flows	22			(1		)	5
Balance as of end of year	$	87		$	64		$	63