Organization and Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Change in ARO (asset retirement obligation)
Beginning Balance			$ 145
Accretion expense			8
Additions			8
Revisions			12
Settlements			(24)
Ending Balance	149		149
Less: Current portion of ARO	(6)		(6)		(10)
Total long-term ARO	143		143		135
Organization and Summary of Significant Accounting Policies (Textuals) [Abstract]
Realized interest income and gains on investment securities	1.0	0.3	2.0	1.0
Crude oil inventory (in barrels)	740,000		740,000		239,000
Crude oil inventory	49		49		19
Capitalization of internal costs per full cost method of accouting	$ 29	$ 30	$ 87	$ 81
Discount rate			10.00%
Unweighted average commodity price of natural gas based on first-day-of-the-month prices for the prior 12 months (per MMBtu)	2.83		2.83
Unweighted average commodity price of oil based on first-day-of-the-month prices for the prior 12 months (per barrel)	95.05		95.05