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Commitments and Contingencies - Additional Information 1 (Detail) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Jun. 30, 2013
Dec. 31, 2012
Loss Contingencies [Line Items]    
Receivables for recoverable costs $ 49 $ 51
Contractual commitments to acquire property, plant and equipment and advance funds to equity method investees 870  
Galveston Bay Refinery and Related Assets [Member]
   
Loss Contingencies [Line Items]    
Contingent consideration 700  
Standby Letters Of Credit [Member] | TAME [Member] | Financial Guarantee [Member]
   
Loss Contingencies [Line Items]    
Credit agreement expiration date Dec. 31, 2018  
Maximum potential undiscounted payments $ 25  
Percentage of credit agreement agreed to reimburse 50.00%