Balance Sheet Components Other Current Assets (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Other Current Assets [Line Items]
Prepaid expenses	$ 25	$ 37
Current deferred income tax asset	37	51
Assets from price risk management activities	1	4
Other	0	1
Other current assets	$ 63	$ 93