Balance Sheet Components (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for Doubtful Accounts Receivable, Current	$ 6	$ 6	$ 5	$ 6
Finite-Lived Intangible Assets, Accumulated Amortization	156		151
Amortization of Intangible Assets	5	5
Sale Leaseback Transaction, Construction Cost		10
Line of Credit Facility scheduled to terminate in 2017	400
Credit Facilities - $300 million revolver	300
Debt Instrument, Covenant Description	.65
Ratio of Indebtedness to Net Capital	0.482
Authorized Short-Term Debt	700
Borrowings	0
Letters of Credit Issued	52
Line of Credit Facility, Remaining Borrowing Capacity	648
Commercial Paper	$ 0