XML 52 R27.htm IDEA: XBRL DOCUMENT v2.4.0.6
Per Unit Performance Data and Other Supplemental Financial Data (Detail) (USD $)
 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Dec. 06, 2007
Per Unit Operating Performance:      
Net Asset Value Per Unit, Beginning $ 43.46 $ 42.91 $ 50.00
Total income (loss) $ (5.40) $ 1.07  
Net expenses $ (0.16) $ (0.19)  
Net increase (decrease) in net asset value $ (5.56) $ 0.88  
Net Asset Value Per Unit, Ending $ 37.90 $ 43.79 $ 50.00
Total Return (12.79%) 2.05%  
Ratios to Average Net Assets      
Total income (loss) (10.50%) 2.93%  
Expenses excluding management fees 0.15% [1] 0.23% [1]  
Management fees 0.60% [1] 0.60% [1]  
Net income (loss) (10.87%) 2.52%  
[1] Annualized