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Asset Retirement Obligations (Details) (ARIZONA PUBLIC SERVICE COMPANY, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Apr. 21, 2011 Y	Dec. 31, 2008 Y
ARIZONA PUBLIC SERVICE COMPANY
Asset Retirement Obligations
License extension approved by the NRC (in years)			20	20
Change in asset retirement obligations
Asset retirement obligations at the beginning of year	$ 329	$ 302
Changes attributable to:
Accretion expense	19	22
Estimated cash flow revisions	(68)	5
Asset retirement obligations at the end of year	$ 280	$ 329

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

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- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

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