Debt (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Line of Credit Facility [Line Items]
Write Off of Unamortized Discount Associated With Redeemed Debt	$ 14	$ 0	$ 0
Junior Subordinated debt [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Description	We issued junior subordinated notes in May 2002. The notes consisted of: (i) a $100 million junior subordinated notes, due July 2012, which carried a 7.5% interest rate (through May 2007, the note was non-interest bearing), and (ii) a $50 million junior subordinated note, due July 2012, which also incurred interest at 7.5%.
Debt Instrument, Issuance Date	May 2002
Debt Instrument, Present Value	61
Debt Instrument, Redemption Date	May 2011
Write Off of Unamortized Discount Associated With Redeemed Debt	13
Junior Subordinated Note 1 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount	100
Debt Instrument, Maturity Date Range, End	July 2012
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Debt Instrument, Discounted Interest Rate	15.625%
Junior Subordinated Note 2 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Face Amount	50
Debt Instrument, Maturity Date Range, End	July 2012
Debt Instrument, Interest Rate, Stated Percentage	7.50%
Debt Instrument, Discounted Interest Rate	14.375%
6 1/4% Senior Notes Due 2012 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Description	We issued $450 million aggregate principal amount of 61/4% senior notes due November 2012 in November 2005. The notes have a seven-year maturity with no sinking fund requirements and are not callable.
Debt Instrument, Issuance Date	November 2005
Debt Instrument, Face Amount	450
Debt Instrument Interest Rate	6 1/4
Debt Instrument, Years to Maturity	7
Debt Instrument, Sinking Fund Description	0
Debt Instrument, Maturity Date Range, End	November 2012
6 5/8% Senior Notes Due 2015 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Description	We issued $450 million aggregate principal amount of 65/8% senior notes due November 2015 in November 2005. The notes have a ten-year maturity with no sinking fund requirements and are subject to optional redemption by Tesoro beginning November 2010 at premiums of 3.3% through October 2011; 2.2% from November 2011 to October 2012; 1.1% from November 2012 to October 2013; and at par thereafter.
Debt Instrument, Issuance Date	November 2005
Debt Instrument, Face Amount	450
Debt Instrument Interest Rate	6 5/8
Debt Instrument, Years to Maturity	10
Debt Instrument, Sinking Fund Description	0
Debt Instrument, Maturity Date Range, End	November 2015
6 1/2% Senior Notes Due 2017 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Description	We issued $500 million aggregate principal amount of 61/2% senior notes due June 2017 in May 2007. The notes have a ten-year maturity with no sinking fund requirements and are subject to optional redemption by Tesoro beginning June 2012 at premiums of 3.25% through May 2013; 2.17% from June 2013 through May 2014; 1.08% from June 2014 through May 2015; and at par thereafter.
Debt Instrument, Issuance Date	May 2007
Debt Instrument, Face Amount	500
Debt Instrument Interest Rate	6 1/2
Debt Instrument, Years to Maturity	10
Debt Instrument, Sinking Fund Description	0
Debt Instrument, Maturity Date Range, End	June 2017
9 3/4% Senior Notes Due 2019 (net of unamortized discount of $10) Member]
Line of Credit Facility [Line Items]
Debt Instrument, Description	We issued $300 million aggregate principal amount of 93/4% senior notes, due June 2019, for general corporate purposes in June 2009. The notes were issued at 96.172% of face value at an effective interest rate of 10.375%. The notes have a ten-year maturity with no sinking fund requirements and are subject to optional redemption by Tesoro beginning June 1, 2014 at premiums of 4.875% through May 31, 2015; 3.25% from June 1, 2015 through May 31, 2016; 1.625% from June 1, 2016 through May 31, 2017; and at par thereafter. We have the right to redeem up to 35% of the aggregate principal amount at 109.75% of face value with proceeds from certain equity issuances through June 1, 2012.
Debt Instrument, Issuance Date	June 2009
Debt Instrument, Face Value Percentage	96.172%
Debt Instrument, Face Amount	300
Debt Instrument Interest Rate	9 3/4
Debt Instrument, Years to Maturity	10
Debt Instrument, Sinking Fund Description	0
Debt Instrument, Maturity Date Range, End	June 2019
Debt Instrument, Interest Rate, Effective Percentage	10.375%
6 1/2% Senior Notes Due 2017 [Member]
Line of Credit Facility [Line Items]
Amount of Debt Redeemed	27
Repayments of Long-term Debt	28
6 1/4% Senior Notes Due 2012 [Member]
Line of Credit Facility [Line Items]
Amount of Debt Redeemed	151
Repayments of Long-term Debt	$ 161