Schedule of Investments (Parenthetical) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
NYMEX RBOB Gasoline Futures RB February 2014 contracts, expiring January 2014 | Open Cleared Swap and Futures Contracts | Open Futures Contracts, Long
   
Expiration date January 2014  
NYMEX RBOB Gasoline Futures RB February 2013 contracts, expiring January 2013 | Open Cleared Swap and Futures Contracts | Open Futures Contracts, Long
   
Expiration date   January 2013
US Treasury Bill Securities | US Treasury Securities | Cash Equivalents
   
Expiration date 3/27/2014 1/17/2013
Interest rate 0.07% 0.10%
United States | NYMEX RBOB Gasoline Futures RB February 2014 contracts, expiring January 2014 | Open Cleared Swap and Futures Contracts
   
Debt Instrument, Collateral Amount $ 2,053,484  
United States | NYMEX RBOB Gasoline Futures RB February 2013 contracts, expiring January 2013 | Open Cleared Swap and Futures Contracts
   
Debt Instrument, Collateral Amount   $ 5,170,256