Asset Retirement Obligations (Tables)

12 Months Ended

Dec. 31, 2012

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Asset Retirement Obligations [Table Text Block]

AROs consist of the following (in millions):

	As of December 31,
	2012		2011
Trojan decommissioning activities	$	42	$	37
Utility plant	39		38
Non-utility property	13		12
Asset retirement obligations	$	94	$	87

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,
	2012			2011			2010
Balance as of beginning of year	$	87		$	64		$	63
Liabilities incurred	—			1			1
Liabilities settled	(3		)	(4		)	(3		)
Accretion expense	6			4			4
Revisions in estimated cash flows	4			22			(1		)
Balance as of end of year	$	94		$	87		$	64