Asset Retirement Obligation Increase related to Boardman plant due to updated decommissioning study.

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FERC-authorized short-term debt through February 6, 2012

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Portion of $370 million credit facility scheduled to terminate in July 2012

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Preliminary engineering costs transferred to construction work in progress during the period

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A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Total Aggregate Indebtedness divided by Net Capital.

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Balance Sheet Components (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Dec. 31, 2009
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for Doubtful Accounts Receivable, Current	$ 5	$ 5	$ 5	$ 5	$ 5	$ 5
Preliminary engineering transferred to construction work in progress			7	0
Finite-Lived Intangible Assets, Accumulated Amortization	147		147		133
Amortization of Intangible Assets	5	4	14	13
Asset Retirement Obligation Increase related to Boardman plant			23
Credit Facilities - $370 million revolver	370		370
Portion of $370 million credit facility scheduled to terminate in July 2012	10		10
Portion of $370 million credit facility scheduled to terminate in July 2013	360		360
Credit Facility $200 million revolver	200		200
Credit Facility $30 million revolver	30		30
Debt Instrument, Covenant Description			0.65
Ratio of Indebtedness to Net Capital	0.521		0.521
Authorized Short-Term Debt	750		750
Line of Credit Facility, Amount Outstanding	89		89
Commercial Paper	0		0
Line of Credit Facility, Remaining Borrowing Capacity	$ 511		$ 511