Balance Sheet Components (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Valuation and Qualifying Accounts Disclosure [Line Items]
Allowance for Doubtful Accounts Receivable, Current	$ 6	$ 5	$ 6	$ 5	$ 6	$ 5
Finite-Lived Intangible Assets, Accumulated Amortization	164		164		153
Amortization of Intangible Assets	6	5	11	9
Sale Leaseback Transaction, Construction Cost			10
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 Facilities - $300 million revolver	300		300
Debt Instrument, Covenant Description			0.650
Ratio of Indebtedness to Net Capital	0.505		0.505
Authorized Short-Term Debt	700		700
Borrowings	0		0
Letters of Credit Issued	115		115
Line of Credit Facility, Remaining Borrowing Capacity	$ 555		$ 555