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Balance Sheet Components Allowance for Uncollectible Accounts (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Allowance for Uncollectible Accounts
Balance as of begining of period	$ 6	$ 5
Provision, net	6	6
Amounts written off, less recoveries	(6)	(6)
Balance as of end of period	$ 6	$ 5

Amount of the current period expense charged against operations, the offset which is generally to the allowance for doubtful accounts for the purpose of reducing receivables, including notes receivable, to an amount that approximates their net realizable value (the amount expected to be collected).

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