Organization and Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014 MBbls	Dec. 31, 2013 MBbls	Dec. 31, 2012	Mar. 31, 2014	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ 1,000,000	$ 1,000,000	$ (6,000,000)		$ (9,000,000)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	(2,000,000)	1,000,000	(1,000,000)		(1,000,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(1,000,000)	2,000,000	(7,000,000)		(10,000,000)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	0		3,000,000
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax	(3,000,000)	2,000,000	0
Other Comprehensive Income (Loss), Net of Tax	(3,000,000)	9,000,000	3,000,000
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(3,000,000)	9,000,000	3,000,000
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Including OTTI		7,000,000
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, Net of Tax		4,000,000
Change in asset retirement obligations [Line Items]
Less: Current portion of ARO	(3,000,000)	(54,000,000)
Asset Retirement Obligations, Noncurrent	183,000,000	201,000,000
Statement [Line Items]
Property, Plant and Equipment, Useful Life	25 years 0 months 0 days
Crude oil inventory in barrels	240,000	23,000
Capitalization of internal costs per full cost method of accounting	199,000,000	198,000,000	191,000,000
Document Fiscal Year Focus	2014
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)	4.35	3.67	2.76
Unweighted average commodity price of oil based on first-day-of-the-month prices for the prior 12 months (per barrel)	94.98	96.82	94.84
Capitalized Costs Exceeding Ceiling, Net			948,000,000
Unrealized loss on post-retirement benefits	(2,000,000)	1,000,000	(1,000,000)		(1,000,000)
Inventory Write-down	9,000,000		8,000,000
Asset retirement obligation liabilities settled through property sales	10,000,000		28,000,000
Primary Derivative Counterparties	10
Total Derivative Counterparties	16
Percent of future hedged production with primary counterparties	85.00%
Number of counterparties holding more than 25 percent of future hedge position.	0
Concentraction Of Future Hedged Production	15.00%
ConcentrationOfCounterpartiesUnderCreditFacility	40.00%
China [Member]
Statement [Line Items]
UnamortizedCostCapitalizedLessRelatedDeferredIncomeTaxesCeilingLimitationCushion	150,000,000
Domestic [Member]
Statement [Line Items]
UnamortizedCostCapitalizedLessRelatedDeferredIncomeTaxesCeilingLimitationCushion	400,000,000
Capitalized Cost Exceeding Ceiling, Gross			1,500,000,000
Sunoco Logistics Partners [Member]
Statement [Line Items]
Sales of oil and gas to customer	10.00%	13.00%
Royal Dutch Shell [Member]
Statement [Line Items]
Sales of oil and gas to customer		12.00%	14.00%
Tesoro Corporation [Member]
Statement [Line Items]
Sales of oil and gas to customer	12.00%	11.00%	14.00%
Big West Oil [Member]
Statement [Line Items]
Sales of oil and gas to customer			10.00%
Minimum [Member]
Statement [Line Items]
Property, Plant and Equipment, Useful Life	3 years 0 months 0 days
Maximum [Member]
Statement [Line Items]
Property, Plant and Equipment, Useful Life	7 years 0 months 0 days
Auction Rate Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Proceeds from Sale of Available-for-sale Securities	39,000,000			39,000,000
Continuing Operations [Member]
Change in asset retirement obligations [Line Items]
Beginning Balance	122,000,000	102,000,000	108,000,000	122,000,000
Accretion expense	8,000,000	8,000,000	8,000,000
Additions	58,000,000	12,000,000	20,000,000
Revisions	16,000,000	8,000,000	12,000,000
Settlements	(18,000,000)	(8,000,000)	(46,000,000)
Ending Balance	186,000,000	122,000,000	102,000,000
Less: Current portion of ARO	(3,000,000)	(5,000,000)	(5,000,000)
Asset Retirement Obligations, Noncurrent	183,000,000	117,000,000	97,000,000
China [Member]
Change in asset retirement obligations [Line Items]
Additions	28,000,000
Domestic [Member]
Change in asset retirement obligations [Line Items]
Additions	30,000,000
Reclassification out of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		0
Other Comprehensive Income (Loss), Net of Tax		4,000,000
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Including OTTI		4,000,000
Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive (Income) Loss, Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax		2,000,000
Other Comprehensive Income (Loss), Net of Tax		5,000,000
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Including OTTI		$ 3,000,000