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FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS - Additional Information (Detail) (USD $) | 3 Months Ended | 12 Months Ended
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Dec. 31, 2012 | Sep. 30, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
USCF Management Fee |  |  |  |  |  |  |  |  | US12NG is contractually obligated to pay USCF a fee, which is paid monthly, equal to 0.75% per annum of average daily total net assets. |  |
Percentage of average daily net assets | 0.75% |  |  |  |  |  |  |  | 0.75% |  |
Estimated directors' fees and expenses |  |  |  |  |  |  |  |  | $ 5,704 | $ 607,582 | $ 1,107,140
Licensing fee incurred |  |  |  |  |  |  |  |  | 5,674 | 7,565 | 8,499
Expense waiver (Note 3) | (26,148) | (13,434) | (12,614) | (16,307) | 0 | (39,596) | (35,903) | (37,670) | (68,503) | (113,169) | (151,688)
Portion Of Non Interest Expense Directors Fees |  |  |  |  |  |  |  |  | 0 | 3,808 | 7,517
Licensing Agreements | First $1,000,000,000 of combined net assets of the funds |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Fee percentage |  |  |  |  |  |  |  |  | 0.04% |  |
Licensing Agreements | First $1,000,000,000 of combined net assets of the funds | Maximum |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Combined assets basis for determining fee percentage | 1,000,000,000 |  |  |  |  |  |  |  | 1,000,000,000 |  |
Licensing Agreements | Combined net assets above $1,000,000,000 |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Fee percentage |  |  |  |  |  |  |  |  | 0.02% |  |
Licensing Agreements | Combined net assets above $1,000,000,000 | Minimum |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Combined assets basis for determining fee percentage | 1,000,000,000 |  |  |  |  |  |  |  | 1,000,000,000 |  |
Licensing Agreements | On and after October 20, 2011 |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Fee percentage |  |  |  |  |  |  |  |  | 0.015% |  |
Assets basis for determining fee percentage |  |  |  |  |  |  |  |  | On all net assets |  |
Future Period - for the year ending December 31, 2012 |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimated investor tax reporting cost |  |  |  |  |  |  |  |  | 75,000 | 55,000 | 155,000
Future Period - for the year ending December 31, 2012 | Maximum |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Costs and expenses annual limit for reimbursement |  |  |  |  |  |  |  |  | 0.15% |  |
Us12ng [Member] |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Portion Of Non Interest Expense Directors Fees |  |  |  |  |  |  |  |  | 68,503 |  |
Us12ng [Member] | Related Public Funds [Member] |  |  |  |  |  |  |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimated directors' fees and expenses |  |  |  |  |  |  |  |  | $ 540,586 |  |

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- Definition Description of the nature of payments to managing member or general partner for management of the day-to-day business functions of the limited liability company (LLC) or limited partnership (LP), including the fee rate, basis of calculation, relevant accounting period, whether the fee is paid to an entity other than the managing member or general partner, or whether the fee is waived. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 57 -Paragraph 2 -Subparagraph a, b, c, d -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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