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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Credit Facilities - $370 million revolver, with $10 million scheduled to terminate in July 2012 and $360 million scheduled to terminate in July 2013.

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Credit Facility $200 million revolver

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Credit Facility $30 million revolver

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

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Portion of $370 million credit facility scheduled to terminate in July 2013

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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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Total Aggregate Indebtedness divided by Net Capital.

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Balance Sheet Components (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010	Dec. 31, 2009
Valuation and Qualifying Accounts Disclosure [Line Items]
Preliminary engineering transferred to construction work in progress			$ 7	$ 0
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	0.522		0.522
Finite-Lived Intangible Assets, Accumulated Amortization	143		143		133
Allowance for Doubtful Accounts Receivable, Current	5	5	5	5	5	5
Amortization of Intangible Assets	5	4	9	7
Authorized Short-Term Debt	750		750
Line of Credit Facility, Amount Outstanding	126		126
Line of Credit Facility, Remaining Borrowing Capacity	$ 474		$ 474