XML 27 R1.htm IDEA: XBRL DOCUMENT v2.4.0.6
Document and Entity Information
 3 Months Ended
Mar. 31, 2012
Apr. 10, 2012
Document Information [Line Items]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Mar. 31, 2012  
Document Fiscal Year Focus 2012  
Document Fiscal Period Focus Q1  
Trading Symbol USL  
Entity Registrant Name UNITED STATES 12 MONTH OIL FUND, LP  
Entity Central Index Key 0001405528  
Current Fiscal Year End Date --12-31  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   0