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CONTRACTS AND AGREEMENTS - Additional information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Annual Fee for transfer agency services $ 20,000    
Brokerage commissions 14,360 7,002 12,869
Rebalancing Cost 10,995 6,306 10,724
Creation And Redemption Activity Costs 3,365 696 2,145
Average Daily Total Net Asset Percentage 0.04% 0.02% 0.04%
Maximum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Transaction fees per transaction 15    
Commissions per round-turn trade, including applicable exchange and NFA fees for Natural Gas-Related Futures Contracts and options on Futures Contracts 15    
Minimum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Annual Fee for custody, fund accounting and fund administration services 75,000    
Transaction fees per transaction 7    
Commissions per round-turn trade, including applicable exchange and NFA fees for Natural Gas-Related Futures Contracts and options on Futures Contracts 7    
First $500 million of US12NG's, USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Fee percentage 0.06%    
First $500 million of US12NG's, USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets | Maximum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Base amount for determining fee percentage 500,000,000    
US12NG's, USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets greater than $500 million but less than $1 billion
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Fee percentage 0.0465%    
US12NG's, USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets greater than $500 million but less than $1 billion | Maximum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Base amount for determining fee percentage 1,000,000,000    
US12NG's, USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets greater than $500 million but less than $1 billion | Minimum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Base amount for determining fee percentage 500,000,000    
US12NG's, USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets exceed $1 billion
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Fee percentage 0.035%    
US12NG's, USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets exceed $1 billion | Minimum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Base amount for determining fee percentage 1,000,000,000    
Marketing Agreement | US12NG's assets up to $3 billion
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Fee percentage 0.06%    
Marketing Agreement | US12NG's assets up to $3 billion | Maximum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Base amount for determining fee percentage 3,000,000,000    
Marketing Agreement | US12NG's assets in excess of $3 billion
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Fee percentage 0.04%    
Marketing Agreement | US12NG's assets in excess of $3 billion | Minimum
      
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]      
Base amount for determining fee percentage $ 3,000,000,000