United States 12 Month Natural Gas Fund (UNL) 10-K 26 Mar 15 2014 FY Annual report Financial data

Document_And_Entity_Informatio

Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Mar. 23, 2015	Jun. 30, 2014
Document Information [Line Items]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	UNL
Entity Common Stock, Shares Outstanding		1,300,000
Entity Registrant Name	United States 12 Month Natural Gas Fund, LP
Entity Central Index Key	1405513
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Public Float			$17,622,000

Statements_of_Financial_Condit

Statements of Financial Condition (USD $)	Dec. 31, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents (Notes 2 and 5)	$15,113,447	$25,514,584
Equity in trading accounts:
Cash and cash equivalents	5,525,172	949,087
Unrealized gain (loss) on open commodity futures contracts	-4,919,890	1,090,050
Receivable for shares sold	733,461	0
Receivable from General Partner (Note 3)	66,266	100,580
Dividends receivable	247	672
Directors' fees and insurance receivable	1,112	835
ETF transaction fees receivable	350	0
Total assets	16,520,165	27,655,808
Liabilities and Partners' Capital
General Partner management fees payable (Note 3)	11,069	18,345
Professional fees payable	80,049	150,502
Brokerage commissions payable	1,581	2,608
License fees payable	998	1,370
Total liabilities	93,697	172,825
Commitments and Contingencies (Notes 3, 4 and 5)
Partners' Capital
General Partner	0	0
Limited Partners	16,426,468	27,482,983
Total Partners' Capital	16,426,468	27,482,983
Total liabilities and partners' capital	$16,520,165	$27,655,808
Limited Partners' shares outstanding	1,200,000	1,500,000
Net asset value per share	$13.69	$18.32
Market value per share	$13.81	$18.35

Schedule_of_Investments

Schedule of Investments (USD $)	Dec. 31, 2014		Dec. 31, 2013
United States [Member] | Money Market Funds [Member]
Unrealized Gain (Loss) on Open Commodity Contracts	$9,510,692
Market Values			19,522,574
% of Partners' Capital	57.90%		71.04%
United States [Member] | Fidelity Institutional Government Portfolio - Class I [Member] | Money Market Funds [Member]
Principal Amount			2,009,115
Market Values			2,009,115
% of Partners' Capital			7.31%
United States [Member] | Goldman Sachs Financial Square Funds - Government Fund - Class FS [Member] | Money Market Funds [Member]
Unrealized Gain (Loss) on Open Commodity Contracts	1	[1]
Principal Amount	1	[1]	1,002,300
Market Values			1,002,300
% of Partners' Capital	0.00%	[1]	3.65%
United States [Member] | Morgan Stanley Institutional Liquidity Fund - Government Portfolio [Member] | Money Market Funds [Member]
Unrealized Gain (Loss) on Open Commodity Contracts	6,510,691
Principal Amount	6,510,691		6,510,691
Market Values			6,510,691
% of Partners' Capital	39.64%		23.69%
United States [Member] | Wells Fargo Advantage Government Money Market Fund - Class I [Member] | Money Market Funds [Member]
Unrealized Gain (Loss) on Open Commodity Contracts	3,000,000
Principal Amount	3,000,000		10,000,468
Market Values			10,000,468
% of Partners' Capital	18.26%		36.39%
Cash Equivalents [Member] | U.S. Treasury Bill, 0.06%, 4/30/15 [Member] | US Treasury Securities [Member]
Principal Amount	3,000,000
Market Values	2,999,455
% of Partners' Capital	18.26%
Cash Equivalents [Member] | U.S. Treasury Bill, 0.07%, 3/27/2014 [Member] | US Treasury Securities [Member]
Principal Amount			3,000,000
Market Values			2,999,504
% of Partners' Capital			10.91%
Cash Equivalents [Member] | United States [Member]
Unrealized Gain (Loss) on Open Commodity Contracts	12,510,147
Market Values			22,522,078
% of Partners' Capital	76.16%		81.95%
Open Futures Contracts, Long [Member] | United States Contracts [Member]
Number of Contracts	537	[2]	656	[3]
Unrealized Gain (Loss) on Open Commodity Contracts	-4,919,890	[2]	1,090,050	[3]
% of Partners' Capital	-29.95%	[2]	3.97%	[3]
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG February 2015 contracts, expiring January 2015 [Member]
Number of Contracts	44
Unrealized Gain (Loss) on Open Commodity Contracts	-575,580
% of Partners' Capital	-3.50%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG March 2015 contracts, expiring February 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-682,500
% of Partners' Capital	-4.15%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG April 2015 contracts, expiring March 2015 (Member)
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-469,990
% of Partners' Capital	-2.86%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG May 2015 contracts, expiring April 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-487,830
% of Partners' Capital	-2.97%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG June 2015 contracts, expiring May 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-431,920
% of Partners' Capital	-2.63%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG July 2015 contracts, expiring June 2015 [Member]
Number of Contracts	44
Unrealized Gain (Loss) on Open Commodity Contracts	-470,800
% of Partners' Capital	-2.87%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG August 2015 contracts, expiring July 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-383,790
% of Partners' Capital	-2.34%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG September 2015 contracts, expiring August 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-340,100
% of Partners' Capital	-2.07%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG October 2015 contracts, expiring September 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-336,770
% of Partners' Capital	-2.05%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG November 2015 contracts, expiring October 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-284,380
% of Partners' Capital	-1.73%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG December 2015 contracts, expiring November 2015 [Member]
Number of Contracts	44
Unrealized Gain (Loss) on Open Commodity Contracts	-277,720
% of Partners' Capital	-1.69%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG January 2016 contracts, expiring December 2015 [Member]
Number of Contracts	45
Unrealized Gain (Loss) on Open Commodity Contracts	-178,510
% of Partners' Capital	-1.09%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG February 2014 contracts, expiring January 2014 [Member]
Number of Contracts			54
Unrealized Gain (Loss) on Open Commodity Contracts			91,970
% of Partners' Capital			0.34%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG March 2014 contracts, expiring February 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			143,450
% of Partners' Capital			0.52%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG April 2014 contracts, expiring March 2014 [Member]
Number of Contracts			54
Unrealized Gain (Loss) on Open Commodity Contracts			69,830
% of Partners' Capital			0.25%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG May 2014 contracts, expiring April 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			34,850
% of Partners' Capital			0.13%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG June 2014 contracts, expiring May 2014 [Member]
Number of Contracts			54
Unrealized Gain (Loss) on Open Commodity Contracts			19,540
% of Partners' Capital			0.07%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG July 2014 contracts, expiring June 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			84,390
% of Partners' Capital			0.31%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG August 2014 contracts, expiring July 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			101,750
% of Partners' Capital			0.37%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG September 2014 contracts, expiring August 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			198,780
% of Partners' Capital			0.72%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG October 2014 contracts, expiring September 2014 [Member]
Number of Contracts			54
Unrealized Gain (Loss) on Open Commodity Contracts			120,580
% of Partners' Capital			0.44%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG November 2014 contracts, expiring October 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			55,320
% of Partners' Capital			0.20%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG December 2014 contracts, expiring November 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			194,730
% of Partners' Capital			0.71%
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG January 2015 contracts, expiring December 2014 [Member]
Number of Contracts			55
Unrealized Gain (Loss) on Open Commodity Contracts			($25,140)
% of Partners' Capital			-0.09%
[1]	Represents less than 0.005%.
[2]	Collateral amounted to $5,525,172 on open futures contracts.
[3]	Collateral amounted to $949,087 on open futures contracts.

Condensed_Schedule_of_Investme

Condensed Schedule of Investments (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument, Collateral Amount	5,525,172	949,087
Investment Owned, Percent of Net Assets	0.01%
Cash Equivalents [Member] | U.S. Treasury Bill, 0.06%, 4/30/15 [Member] | Us Treasury Securities [Member]
Expiration date	4/30/15
Interest Rate	0.06%
Cash Equivalents [Member] | U.S. Treasury Bill, 0.07%, 3/27/2014 [Member] | Us Treasury Securities [Member]
Interest Rate		0.07%
Cash Equivalents [Member] | United States Contracts [Member] | U.S. Treasury Bill, 0.07%, 3/27/2014 [Member]
Expiration date		3/27/14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG February 2015 contracts, expiring January 2015 [Member]
Expiration date	Jan-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG March 2015 contracts, expiring February 2015 [Member]
Expiration date	Feb-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG April 2015 contracts, expiring March 2015 (Member)
Expiration date	Mar-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG May 2015 contracts, expiring April 2015 [Member]
Expiration date	Apr-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG June 2015 contracts, expiring May 2015 [Member]
Expiration date	May-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG July 2015 contracts, expiring June 2015 [Member]
Expiration date	Jun-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG August 2015 contracts, expiring July 2015 [Member]
Expiration date	Jul-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG September 2015 contracts, expiring August 2015 [Member]
Expiration date	Aug-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG October 2015 contracts, expiring September 2015 [Member]
Expiration date	Sep-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG November 2015 contracts, expiring October 2015 [Member]
Expiration date	Oct-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG December 2015 contracts, expiring November 2015 [Member]
Expiration date	Nov-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG January 2016 contracts, expiring December 2015 [Member]
Expiration date	Dec-15
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG February 2014 contracts, expiring January 2014 [Member]
Expiration date		Jan-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG March 2014 contracts, expiring February 2014 [Member]
Expiration date		Feb-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG April 2014 contracts, expiring March 2014 [Member]
Expiration date		Mar-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG May 2014 contracts, expiring April 2014 [Member]
Expiration date		Apr-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG June 2014 contracts, expiring May 2014 [Member]
Expiration date		May-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG July 2014 contracts, expiring June 2014 [Member]
Expiration date		Jun-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG September 2014 contracts, expiring August 2014 [Member]
Expiration date		Aug-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG October 2014 contracts, expiring September 2014 [Member]
Expiration date		Sep-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG November 2014 contracts, expiring October 2014 [Member]
Expiration date		Oct-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG December 2014 contracts, expiring November 2014 [Member]
Expiration date		Nov-14
Open Futures Contracts, Long [Member] | United States Contracts [Member] | NYMEX Natural Gas Futures NG January 2015 contracts, expiring December 2014 [Member]
Expiration date		Dec-14

Statements_of_Operations

Statements of Operations (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Gain (loss) on trading of commodity futures contracts:
Realized gain (loss) on closed positions	$2,205,950	$2,395,300	($12,161,650)
Change in unrealized gain (loss) on open positions	-6,009,940	1,996,630	7,676,740
Dividend income	2,798	4,719	4,189
Interest income	2,288	4,481	7,257
ETF transaction fees	5,600	9,450	10,500
Total income (loss)	-3,793,304	4,410,580	-4,462,964
Expenses
General Partner management fees (Note 3)	143,944	250,075	283,719
Professional fees	150,833	150,502	125,273
Brokerage commissions	3,918	8,360	14,360
Directors' fees and insurance	6,009	7,620	5,705
License fees	2,879	5,001	5,674
Total expenses	307,583	421,558	434,731
Expense waiver (Note 3)	-128,906	-100,580	-68,503
Net expenses	178,677	320,978	366,228
Net income (loss)	($3,971,981)	$4,089,602	($4,829,192)
Net income (loss) per limited partnership share	($4.63)	$1.09	($3.98)
Net income (loss) per weighted average limited partnership share	($3.85)	$2.19	($2.26)
Weighted average limited partnership shares outstanding	1,031,781	1,866,712	2,132,514

Statements_of_Changes_in_Partn

Statements of Changes in Partners' Capital (USD $)	Total	General Partner [Member]	Limited Partners [Member]
Balances at Dec. 31, 2011	$21,209,546	$0	$21,209,546
Net asset value, beginning of year at Dec. 31, 2011	$21.21
Addition of partnership shares	33,083,248	0	33,083,248
Redemption of partnership shares	-6,377,911	0	-6,377,911
Net income (loss)	-4,829,192	0	-4,829,192
Balances at Dec. 31, 2012	43,085,691	0	43,085,691
Net asset value, end of year at Dec. 31, 2012	$17.23
Addition of partnership shares	5,962,931	0	5,962,931
Redemption of partnership shares	-25,655,241	0	-25,655,241
Net income (loss)	4,089,602	0	4,089,602
Balances at Dec. 31, 2013	27,482,983	0	27,482,983
Net asset value, end of year at Dec. 31, 2013	$18.32
Addition of partnership shares	4,902,725	0	4,902,725
Redemption of partnership shares	-11,987,259	0	-11,987,259
Net income (loss)	-3,971,981	0	-3,971,981
Balances at Dec. 31, 2014	$16,426,468	$0	$16,426,468
Net asset value, end of year at Dec. 31, 2014	$13.69

Statements_of_Changes_in_Partn1

Statements of Changes in Partners' Capital (Parenthetical)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Addition of partnership share	300,000	350,000	1,850,000
Redemption of partnership units	600,000	1,350,000	350,000

Statements_of_Cash_Flows

Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash Flows from Operating Activities:
Net income (loss)	($3,971,981)	$4,089,602	($4,829,192)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
(Increase) decrease in commodity futures trading account - cash and cash equivalents	-4,576,085	3,466,968	5,715,124
Unrealized (gain) loss on futures contracts	6,009,940	-1,996,630	-7,676,740
(Increase) decrease in receivable from General Partner	34,314	-32,077	44,666
(Increase) decrease in dividends receivable	425	-249	-228
(Increase) decrease in interest receivable	0	0	8
(Increase) decrease in directors' fees and insurance receivable	-277	-688	526
(Increase) decrease in ETF transaction fees receivable	-350	0	0
Increase (decrease) in investment payable	0	0	-8
Increase (decrease) in General Partner management fees payable	-7,276	-10,280	13,964
Increase (decrease) in professional fees payable	-70,453	25,229	-25,802
Increase (decrease) in brokerage commissions payable	-1,027	-1,400	-252
Increase (decrease) in license fees payable	-372	-790	714
Net cash provided by (used in) operating activities	-2,583,142	5,539,685	-6,757,220
Cash Flows from Financing Activities:
Addition of partnership shares	4,169,264	5,962,931	33,083,248
Redemption of partnership shares	-11,987,259	-25,655,241	-6,377,911
Net cash provided by (used in) financing activities	-7,817,995	-19,692,310	26,705,337
Net Increase (Decrease) in Cash and Cash Equivalents	-10,401,137	-14,152,625	19,948,117
Cash and Cash Equivalents, beginning of year	25,514,584	39,667,209	19,719,092
Cash and Cash Equivalents, end of year	$15,113,447	$25,514,584	$39,667,209

ORGANIZATION_AND_BUSINESS

ORGANIZATION AND BUSINESS	12 Months Ended
	Dec. 31, 2014
Organization and Business [Abstract]
Organization and Business	NOTE 1 - ORGANIZATION AND BUSINESS
	The United States 12 Month Natural Gas Fund, LP (“UNL”) was organized as a limited partnership under the laws of the state of Delaware on June 27, 2007. UNL is a commodity pool that issues limited partnership shares (“shares”) that may be purchased and sold on the NYSE Arca, Inc. (the “NYSE Arca”). UNL will continue in perpetuity, unless terminated sooner upon the occurrence of one or more events as described in its Second Amended and Restated Agreement of Limited Partnership dated as of March 1, 2013 (the “LP Agreement”). The investment objective of UNL is for the daily changes in percentage terms of its shares’ per share net asset value (“NAV”) to reflect the daily changes in percentage terms of the spot price of natural gas delivered at the Henry Hub, Louisiana, as measured by the daily changes in the average of the prices of 12 futures contracts on natural gas traded on the New York Mercantile Exchange (the “NYMEX”), consisting of the near month contract to expire and the contracts for the following 11 months for a total of 12 consecutive months’ contracts, except when the near month contract is within two weeks of expiration, in which case it will be measured by the futures contracts that are the next month contract to expire and the contracts for the following 11 consecutive months (the “Benchmark Futures Contracts”), less UNL’s expenses. It is not the intent of UNL to be operated in a fashion such that the per share NAV will equal, in dollar terms, the spot price of natural gas or any particular futures contract based on natural gas. It is not the intent of UNL to be operated in a fashion such that its per share NAV will reflect the percentage change of the price of any particular futures contract as measured over a time period greater than one day. United States Commodity Funds LLC (“USCF”), the general partner of UNL, believes that it is not practical to manage the portfolio to achieve such an investment goal when investing in Futures Contracts (as defined below) and Other Natural Gas-Related Investments (as defined below). UNL accomplishes its objective through investments in futures contracts for natural gas, crude oil, diesel-heating oil, gasoline and other petroleum-based fuels that are traded on the NYMEX, ICE Futures or other U.S. and foreign exchanges (collectively, “Futures Contracts”) and other natural gas-related investments such as cash-settled options on Futures Contracts, forward contracts for natural gas, cleared swap contracts and over-the-counter transactions that are based on the price of natural gas, crude oil and other petroleum-based fuels, Futures Contracts and indices based on the foregoing (collectively, “Other Natural Gas-Related Investments”). As of December 31, 2014, UNL held 537 Futures Contracts for natural gas traded on the NYMEX and did not hold any Futures Contracts traded on ICE Futures.
	UNL commenced investment operations on November 18, 2009 and has a fiscal year ending on December 31. USCF is responsible for the management of UNL. USCF is a member of the National Futures Association (the “NFA”) and became a commodity pool operator registered with the Commodity Futures Trading Commission (the “CFTC”) effective December 1, 2005. USCF is also the general partner of the United States Oil Fund, LP (“USO”), the United States Natural Gas Fund, LP (“UNL”), the United States 12 Month Oil Fund, LP (“USL”), the United States Gasoline Fund, LP (“UGA”) and the United States Diesel-Heating Oil Fund, LP (“UHN”), which listed their limited partnership shares on the AMEX under the ticker symbols “USO” on April 10, 2006, “UNL” on April 18, 2007, “USL” on December 6, 2007, “UGA” on February 26, 2008 and “UHN” on April 9, 2008, respectively. As a result of the acquisition of the American Stock Exchange (the “AMEX”) by NYSE Euronext, each of USO’s, UNL’s, USL’s, UGA’s and UHN’s shares commenced trading on the NYSE Arca on November 25, 2008. USCF is also the general partner of the United States Short Oil Fund, LP (“DNO”) and the United States Brent Oil Fund, LP (“BNO”), which listed their limited partnership shares on the NYSE Arca under the ticker symbols “DNO” on September 24, 2009 and “BNO” on June 2, 2010, respectively. USCF is also the sponsor of the United States Commodity Index Fund (“USCI”), the United States Copper Index Fund (“CPER”), the United States Agriculture Index Fund (“USAG”) and the United States Metals Index Fund (“USMI”), each a series of the United States Commodity Index Funds Trust. USCI, CPER, USAG and USMI listed their shares on the NYSE Arca under the ticker symbol “USCI” on August 10, 2010, “CPER” on November 15, 2011, “USAG” on April 13, 2012 and “USMI” on June 19, 2012, respectively. All funds listed previously are referred to collectively herein as the “Related Public Funds.” On January 30, 2015, USCF as the sponsor of United States Commodity Index Funds Trust (the “Trust”) and its series USMI announced that its officers and members had authorized a plan to (i) liquidate USMI, (ii) terminate the continuous offering of USMI, and (iii) deregister USMI under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and therefore, terminate the Trust’s obligation to include USMI on its periodic and current reports with the Securities and Exchange Commission (“SEC”). USCF has submitted written notice to the NYSE Arca of its decision to liquidate USMI, terminate the offering and to terminate USMI’s obligations under the Exchange Act.
	USCF intends to file a post-effective amendment on behalf of the Trust and USMI to terminate the offering of the registered and unsold shares of USMI. The NYSE Arca will file a Form 25 with the SEC to affect the withdrawal of the listing of USMI from the NYSE Arca. Delisting from the NYSE Arca will become effective 10 days after the filing date of the Form 25. Provided that USMI continues to meet the applicable legal requirements, USCF intends to file a Form 15 on behalf of the Trust and USMI with the SEC in early April 2015 to suspend the Trust’s duty to include USMI on its reports under Sections 13(a) and 15(d) of the Exchange Act. USMI expects the termination of registration will become effective 90 days after the date of the filing of the Form 15 with the SEC.
	UNL issues shares to certain authorized purchasers (“Authorized Participants”) by offering baskets consisting of 50,000 shares (“Creation Baskets”) through ALPS Distributors, Inc. as its marketing agent (“ALPS Distributors” or the “Marketing Agent”). The purchase price for a Creation Basket is based upon the NAV of a share calculated shortly after the close of the core trading session on the NYSE Arca on the day the order to create the basket is properly received.
	From July 1, 2011 through December 31, 2014 (and continuing at least through April 30, 2015), the applicable transaction fee paid by Authorized Participants is $350 to UNL for each order they place to create or redeem one or more baskets (“Redemption Baskets”); prior to July 1, 2011, this fee was $1,000. Shares may be purchased or sold on a nationally recognized securities exchange in smaller increments than a Creation Basket or Redemption Basket. Shares purchased or sold on a nationally recognized securities exchange are not purchased or sold at the per share NAV of UNL but rather at market prices quoted on such exchange.
	In November 2009, UNL initially registered 30,000,000 shares on Form S-1 with the SEC. On November 18, 2009, UNL listed its shares on the NYSE Arca under the ticker symbol “UNL”. On that day, UNL established its initial per share NAV by setting the price at $50.00 and issued 200,000 shares in exchange for $10,000,000. UNL also commenced investment operations on November 18, 2009 by purchasing Futures Contracts traded on the NYMEX based on natural gas. As of December 31, 2014, UNL had registered a total of 25,600,000 shares.

SUMMARY_OF_SIGNIFICANT_ACCOUNT

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2014
Summary Of Significant Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE 2 - SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Revenue Recognition
	Commodity futures contracts, forward contracts, physical commodities and related options are recorded on the trade date. All such transactions are recorded on the identified cost basis and marked to market daily. Unrealized gains or losses on open contracts are reflected in the statements of financial condition and represent the difference between the original contract amount and the market value (as determined by exchange settlement prices for futures contracts and related options and cash dealer prices at a predetermined time for forward contracts, physical commodities, and their related options) as of the last business day of the year or as of the last date of the financial statements. Changes in the unrealized gains or losses between periods are reflected in the statements of operations. UNL earns interest on its assets denominated in U.S. dollars on deposit with the futures commission merchant (“FCM”) at the overnight Federal Funds Rate less 32 basis points. In addition, UNL earns income on funds held at the custodian or FCM at prevailing market rates earned on such investments.
	Brokerage Commissions
	Brokerage commissions on all open commodity futures contracts are accrued on a full-turn basis.
	Income Taxes
	UNL is not subject to federal income taxes; each partner reports his/her allocable share of income, gain, loss deductions or credits on his/her own income tax return.
	In accordance with accounting principles generally accepted in the United States of America (“GAAP”), UNL is required to determine whether a tax position is more likely than not to be sustained upon examination by the applicable taxing authority, including resolution of any tax related appeals or litigation processes, based on the technical merits of the position. UNL files an income tax return in the U.S. federal jurisdiction, and may file income tax returns in various U.S. states. UNL is not subject to income tax return examinations by major taxing authorities for years before 2011. The tax benefit recognized is measured as the largest amount of benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. De-recognition of a tax benefit previously recognized results in UNL recording a tax liability that reduces net assets. However, UNL’s conclusions regarding this policy may be subject to review and adjustment at a later date based on factors including, but not limited to, on-going analysis of and changes to tax laws, regulations and interpretations thereof. UNL recognizes interest accrued related to unrecognized tax benefits and penalties related to unrecognized tax benefits in income tax fees payable, if assessed. No interest expense or penalties have been recognized as of and for the year ended December 31, 2014.
	Creations and Redemptions
	Authorized Participants may purchase Creation Baskets or redeem Redemption Baskets only in blocks of 50,000 shares at a price equal to the NAV of the shares calculated shortly after the close of the core trading session on the NYSE Arca on the day the order is placed.
	UNL receives or pays the proceeds from shares sold or redeemed within three business days after the trade date of the purchase or redemption. The amounts due from Authorized Participants are reflected in UNL’s statements of financial condition as receivable for shares sold, and amounts payable to Authorized Participants upon redemption are reflected as payable for shares redeemed.
	Partnership Capital and Allocation of Partnership Income and Losses
	Profit or loss shall be allocated among the partners of UNL in proportion to the number of shares each partner holds as of the close of each month. USCF may revise, alter or otherwise modify this method of allocation as described in the LP Agreement.
	Calculation of Per Share Net Asset Value (“NAV”)
	UNL’s per share NAV is calculated on each NYSE Arca trading day by taking the current market value of its total assets, subtracting any liabilities and dividing that amount by the total number of shares outstanding. UNL uses the closing price for the contracts on the relevant exchange on that day to determine the value of contracts held on such exchange.
	Net Income (Loss) Per Share
	Net income (loss) per share is the difference between the per share NAV at the beginning of each period and at the end of each period. The weighted average number of shares outstanding was computed for purposes of disclosing net income (loss) per weighted average share. The weighted average shares are equal to the number of shares outstanding at the end of the period, adjusted proportionately for shares added and redeemed based on the amount of time the shares were outstanding during such period. There were no shares held by USCF at December 31, 2014.
	Offering Costs
	Offering costs incurred in connection with the registration of additional shares after the initial registration of shares are borne by UNL. These costs include registration fees paid to regulatory agencies and all legal, accounting, printing and other expenses associated with such offerings. These costs are accounted for as a deferred charge and thereafter amortized to expense over twelve months on a straight-line basis or a shorter period, if warranted.
	Cash Equivalents
	Cash equivalents include money market funds and overnight deposits or time deposits with original maturity dates of six months or less.
	Reclassification
	Certain amounts in the accompanying financial statements were reclassified to conform with the current presentation.
	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires USCF to make estimates and assumptions that affect the reported amount of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of the revenue and expenses during the reporting period. Actual results may differ from those estimates and assumptions.

FEES_PAID_BY_THE_FUND_AND_RELA

FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS	12 Months Ended
	Dec. 31, 2014
Fees Paid By Fund and Related Party Transactions [Abstract]
Fees Paid by the Fund and Related Party Transactions	NOTE 3 - FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS
	USCF Management Fee
	Under the LP Agreement, USCF is responsible for investing the assets of UNL in accordance with the objectives and policies of UNL. In addition, USCF has arranged for one or more third parties to provide administrative, custody, accounting, transfer agency and other necessary services to UNL. For these services, UNL is contractually obligated to pay USCF a fee, which is paid monthly, that is equal to 0.75% per annum of average daily total net assets.
	Ongoing Registration Fees and Other Offering Expenses
	UNL pays all costs and expenses associated with the ongoing registration of its shares subsequent to the initial offering. These costs include registration or other fees paid to regulatory agencies in connection with the offer and sale of shares, and all legal, accounting, printing and other expenses associated with such offer and sale. For the years ended December 31, 2014, 2013 and 2012, UNL did not incur any registration fees and other offering expenses.
	Directors’ Fees and Expenses
	UNL is responsible for paying its portion of the directors’ and officers’ liability insurance for UNL and the Related Public Funds and the fees and expenses of the independent directors who also serve as audit committee members of UNL and the Related Public Funds. UNL shares the fees and expenses on a pro rata basis with each Related Public Fund, as described above, based on the relative assets of each fund, computed on a daily basis. These fees and expenses for the year ended December 31, 2014 were $567,863 for UNL and the Related Public Funds. UNL’s portion of such fees and expenses for the year ended December 31, 2014 was $6,009. For the years ended December 31, 2013 and 2012, these fees and expenses were $555,465 and $540,586, respectively, for UNL and the Related Public Funds. UNL’s portion of such fees and expenses was $7,620 and $5,705, respectively.
	Licensing Fees
	UNL and the Related Public Funds, other than BNO, USCI, CPER, USAG and USMI, pay a licensing fee that is equal to 0.015% on all net assets. During the years ended December 31, 2014, 2013 and 2012, UNL incurred $2,879, $5,001 and $5,674, respectively, under this arrangement.
	Investor Tax Reporting Cost
	The fees and expenses associated with UNL’s audit expenses and tax accounting and reporting requirements are paid by UNL. These costs were approximately $86,000, $125,000 and $75,000, respectively, for the years ended December 31, 2014, 2013 and 2012.
	Other Expenses and Fees and Expense Waivers
	In addition to the fees described above, UNL pays all brokerage fees and other expenses in connection with the operation of UNL, excluding costs and expenses paid by USCF as outlined in Note 4 below. USCF has voluntarily agreed to pay certain expenses typically borne by UNL, to the extent that such expenses exceeded 0.15% (15 basis points) of UNL’s NAV, on an annualized basis, through at least June 30, 2015. USCF has no obligation to continue such payment into subsequent periods. For the year ended December 31, 2014, USCF waived $ 128,906 of UNL’s expenses. This voluntary expense waiver is in addition to those amounts USCF is contractually obligated to pay as described in Note 4 – Contracts and Agreements.

CONTRACTS_AND_AGREEMENTS

CONTRACTS AND AGREEMENTS	12 Months Ended
	Dec. 31, 2014
Contracts and Agreements [Abstract]
Contracts and Agreements	NOTE 4 - CONTRACTS AND AGREEMENTS
	UNL is party to a marketing agent agreement, dated as of October 30, 2009, as amended from time to time, with the Marketing Agent and USCF, whereby the Marketing Agent provides certain marketing services for UNL as outlined in the agreement. The fee of the Marketing Agent, which is borne by USCF, is equal to 0.06% on UNL’s assets up to $3 billion; and 0.04% on UNL’s assets in excess of $3 billion. In no event may the aggregate compensation paid to the Marketing Agent and any affiliate of USCF for distribution-related services exceed ten percent (10%) of the gross proceeds of UNL’s offering.
	The above fee does not include website construction and development, which are borne by USCF.
	UNL is also party to a custodian agreement, dated November 3, 2009, as amended from time to time, with Brown Brothers Harriman & Co. (“BBH&Co.”) and USCF, whereby BBH&Co. holds investments on behalf of UNL. USCF pays the fees of the custodian, which are determined by the parties from time to time. In addition, UNL is party to an administrative agency agreement, dated as of November 3, 2009, as amended from time to time, with USCF and BBH&Co., whereby BBH&Co. acts as the administrative agent, transfer agent and registrar for UNL. USCF also pays the fees of BBH&Co. for its services under such agreement and such fees are determined by the parties from time to time.
	Currently, USCF pays BBH&Co. for its services, in the foregoing capacities, a minimum amount of $75,000 annually for its custody, fund accounting and fund administration services rendered to UNL and each of the Related Public Funds, as well as a $20,000 annual fee for its transfer agency services. In addition, USCF pays BBH&Co. an asset-based charge of (a)  0.06% for the first $500 million of the Related Public Funds’ combined net assets, (b)  0.0465% for the Related Public Funds’ combined net assets greater than $500 million but less than $1 billion, and (c)  0.035% once the Related Public Funds’ combined net assets exceed $1 billion. The annual minimum amount will not apply if the asset-based charge for all accounts in the aggregate exceeds $75,000. USCF also pays transaction fees ranging from $7 to $15 per transaction.
	On October 8, 2013, UNL entered into a brokerage agreement with RBC Capital Markets, LLC (“RBC Capital” or “RBC”) to serve as UNL’s futures commission merchant (“FCM”), effective October 10, 2013. Prior to October 10, 2013, the FCM was UBS Securities LLC (“UBS Securities”). The agreements require RBC Capital and UBS Securities to provide services to UNL in connection with the purchase and sale of Futures Contracts and Other Natural Gas-Related Investments that may be purchased and sold by or through RBC Capital and/or UBS Securities for UNL’s account. In accordance with each agreement, RBC Capital and UBS Securities charge UNL commissions of approximately $7 to $15 per round-turn trade, including applicable exchange and NFA fees for Futures Contracts and options on Futures Contracts. Such fees include those incurred when purchasing Futures Contracts and options on Futures Contracts when UNL issues shares as a result of a Creation Basket, as well as fees incurred when selling Futures Contracts and options on Futures Contracts when UNL redeems shares as a result of a Redemption Basket. Such fees are also incurred when Futures Contracts and options on Futures Contracts are purchased or redeemed for the purpose of rebalancing the portfolio. UNL also incurs commissions to brokers for the purchase and sale of Futures Contracts, Other Natural Gas-Related Investments or short term obligations of the United States of two years or less (“Treasuries”).
		For the Year Ended			For the Year Ended			For the Year Ended
		December 31, 2014			December 31, 2013			December 31, 2012
	Total commissions accrued to brokers	$	3,918		$	8,360		$	14,360
	Total commissions as annualized percentage of average total net assets		0.02	%		0.03	%		0.04	%
	Commissions accrued as a result of rebalancing	$	2,126		$	4,484		$	10,995
	Percentage of commissions accrued as a result of rebalancing		54.26	%		53.64	%		76.57	%
	Commissions accrued as a result of creation and redemption activity	$	1,792		$	3,876		$	3,365
	Percentage of commissions accrued as a result of creation and redemption activity		45.74	%		46.36	%		23.43	%
	UNL’s total commissions accrued to brokers for the year ended December 31, 2104, compared to the year ended December 31, 2013, was similar; and was similar for the year ended December 31, 2013, compared to the year ended December 31, 2012, as measured as an annualized percentage of average total net assets. However, there can be no assurance that commission costs and portfolio turnover will not cause commission expenses to rise in future quarters.
	UNL and the NYMEX entered into a licensing agreement on December 4, 2007, as amended on October 20, 2011, whereby UNL was granted a non-exclusive license to use certain of the NYMEX’s settlement prices and service marks. Under the licensing agreement, UNL and the Related Public Funds, other than BNO, USCI, CPER, USAG and USMI, pay the NYMEX an asset-based fee for the license, the terms of which are described in Note 3. UNL expressly disclaims any association with the NYMEX or endorsement of UNL by the NYMEX and acknowledges that “NYMEX” and “New York Mercantile Exchange” are registered trademarks of the NYMEX.

FINANCIAL_INSTRUMENTS_OFFBALAN

FINANCIAL INSTRUMENTS, OFF-BALANCE SHEET RISKS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2014
Financial Instruments Off Balance Sheet Risks and Contingencies [Abstract]
Financial Instruments, Off-Balance Sheet Risks and Contingencies	NOTE 5 - FINANCIAL INSTRUMENTS, OFF-BALANCE SHEET RISKS AND CONTINGENCIES
	UNL engages in the trading of futures contracts, options on futures contracts and cleared swap contracts (collectively, “derivatives”). UNL is exposed to both market risk, which is the risk arising from changes in the market value of the contracts, and credit risk, which is the risk of failure by another party to perform according to the terms of a contract.
	UNL may enter into futures contracts and options on futures contracts and may engage in cleared swap contracts to gain exposure to changes in the value of an underlying commodity. A futures contract obligates the seller to deliver (and the purchaser to accept) the future delivery of a specified quantity and type of a commodity at a specified time and place. Some futures contracts may call for physical delivery of the asset, while others are settled in cash. The contractual obligations of a buyer or seller may generally be satisfied by taking or making physical delivery of the underlying commodity or by making an offsetting sale or purchase of an identical futures contract on the same or linked exchange before the designated date of delivery. Cleared swaps are over-the-counter agreements that are eligible to be cleared by a clearinghouse, but are not traded on an exchange. A cleared swap is created when the parties to an off-exchange over-the-counter swap transaction agree to extinguish their OTC contract and replace with a cleared swap. Cleared swaps are intended to provide the efficiencies and benefits that centralized clearing or an exchange offers to traders of futures contracts, including credit risk intermediation and the ability to offset positions initiated with different counterparties.
	The purchase and sale of futures contracts, options on futures contracts and cleared swaps require margin deposits with a FCM. Additional deposits may be necessary for any loss on contract value. The Commodity Exchange Act requires a FCM to segregate all customer transactions and assets from the FCM’s proprietary activities.
	Futures contracts and cleared swaps involve, to varying degrees, elements of market risk (specifically commodity price risk) and exposure to loss in excess of the amount of variation margin. The face or contract amounts reflect the extent of the total exposure UNL has in the particular classes of instruments. Additional risks associated with the use of futures contracts are an imperfect correlation between movements in the price of the futures contracts and the market value of the underlying securities and the possibility of an illiquid market for a futures contract. Buying and selling options on futures contracts exposes investors to the risks of purchasing or selling futures contracts.
	All of the Futures Contracts held by UNL were exchange-traded futures contracts through December 31, 2014. The risks associated with exchange-traded contracts are generally perceived to be less than those associated with over-the-counter transactions, since, in over-the-counter transactions, a party must rely solely on the credit of its respective individual counterparties. When UNL enters into non-exchange traded contracts (including Exchange for Related Position or EFRP transactions), it is subject to credit risks associated with counterparty non-performance. Over-the-counter transactions subject UNL to the credit risk associated with counterparty non-performance. The credit risk from counterparty non-performance associated with such instruments is the net unrealized gain, if any, on the transaction. UNL has credit risk under its futures contracts since the sole counterparty to all domestic and foreign futures contracts is the clearinghouse for the exchange on which the relevant contracts are traded. In addition, UNL bears the risk of financial failure by the clearing broker.
	UNL’s cash and other property, such as Treasuries, deposited with a FCM are considered commingled with all other customer funds, subject to the FCM’s segregation requirements. In the event of a FCM’s insolvency, recovery may be limited to a pro rata share of segregated funds available. It is possible that the recovered amount could be less than the total of cash and other property deposited. The insolvency of a FCM could result in the complete loss of UNL’s assets posted with that FCM; however, the majority of UNL’s assets are held in cash and/or cash equivalents with UNL’s custodian and would not be impacted by the insolvency of a FCM. The failure or insolvency of UNL’s custodian, however, could result in a substantial loss of UNL’s assets.
	USCF invests a portion of UNL’s cash in money market funds that seek to maintain a stable per share NAV. UNL is exposed to any risk of loss associated with an investment in such money market funds. As of December 31, 2014 and December 31, 2013, UNL held investments in money market funds in the amounts of $9,510,692 and $19,522,574, respectively. UNL also holds cash deposits with its custodian. Pursuant to a written agreement with BBH&Co., uninvested overnight cash balances are swept to offshore branches of U.S. regulated and domiciled banks located in Toronto, Canada; London, United Kingdom; Grand Cayman, Cayman Islands; and Nassau, Bahamas; which are subject to U.S. regulation and regulatory oversight. As of December 31, 2014 and December 31, 2013, UNL held cash deposits and investments in Treasuries in the amounts of $11,127,927 and $6,941,097, respectively, with the custodian and FCM. Some or all of these amounts may be subject to loss should UNL’s custodian and/or FCM cease operations.
	For derivatives, risks arise from changes in the market value of the contracts. Theoretically, UNL is exposed to market risk equal to the value of futures contracts purchased and unlimited liability on such contracts sold short. As both a buyer and a seller of options, UNL pays or receives a premium at the outset and then bears the risk of unfavorable changes in the price of the contract underlying the option.
	UNL’s policy is to continuously monitor its exposure to market and counterparty risk through the use of a variety of financial, position and credit exposure reporting controls and procedures. In addition, UNL has a policy of requiring review of the credit standing of each broker or counterparty with which it conducts business.
	The financial instruments held by UNL are reported in its statements of financial condition at market or fair value, or at carrying amounts that approximate fair value, because of their highly liquid nature and short-term maturity.

FINANCIAL_HIGHLIGHTS

FINANCIAL HIGHLIGHTS	12 Months Ended
	Dec. 31, 2014
Financial Highlights [Abstract]
Financial Highlights	NOTE 6 - FINANCIAL HIGHLIGHTS
	The following table presents per share performance data and other supplemental financial data for the years ended December 31, 2014, 2013 and 2012. This information has been derived from information presented in the financial statements.
		Year Ended			Year Ended			Year Ended
		December 31, 2014			December 31, 2013			December 31, 2012
	Per Share Operating Performance:
	Net asset value, beginning of year	$	18.32		$	17.23		$	21.21
	Total income (loss)		-4.33			1.32			-3.78
	Net expenses		-0.3			-0.23			-0.2
	Net increase (decrease) in net asset value		-4.63			1.09			-3.98
	Net asset value, end of year	$	13.69		$	18.32		$	17.23
	Total Return		-25.27	%		6.33	%		-18.76	%
	Ratios to Average Net Assets
	Total income (loss)		-19.76	%		13.23	%		-11.8	%
	Management fees		0.75	%		0.75	%		0.75	%
	Total expenses excluding management fees		0.85	%		0.51	%		0.4	%
	Expenses waived		-0.67	%		-0.3	%		-0.18	%
	Net expenses excluding management fees		0.18	%		0.21	%		0.22	%
	Net income (loss)		-20.7	%		12.27	%		-12.77	%
	Total returns are calculated based on the change in value during the period. An individual shareholder’s total return and ratio may vary from the above total returns and ratios based on the timing of contributions to and withdrawals from UNL.

QUARTERLY_FINANCIAL_DATA_Unaud

QUARTERLY FINANCIAL DATA (Unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	NOTE 7 - QUARTERLY FINANCIAL DATA (Unaudited)
	The following summarized (unaudited) quarterly financial information presents the results of operations and other data for the three-month periods ended March 31, June 30, September 30 and December 31, 2014 and 2013.
				Second				Fourth
		First Quarter		Quarter		Third Quarter		Quarter
		2014		2014		2014		2014
	Total income (loss)	$	2,154,963	$	59,752	$	-1,333,315	$	-4,674,704
	Total expenses		96,400		85,090		75,491		50,602
	Expense waivers		-38,045		-40,700		-39,383		-10,778
	Net expenses		58,355		44,390		36,108		39,824
	Net income (loss)	$	2,096,608	$	15,362	$	-1,369,423	$	-4,714,528
	Net income (loss) per share	$	1.31	$	-0.07	$	-1.52	$	-4.35
				Second				Fourth
		First Quarter		Quarter		Third Quarter		Quarter
		2013		2013		2013		2013
	Total income (loss)	$	5,182,801	$	-2,870,767	$	-352,278	$	2,450,824
	Total expenses		121,121		100,767		94,831		104,839
	Expense waivers		-14,464		-18,323		-30,231		-37,562
	Net expenses		106,657		82,444		64,600		67,277
	Net income (loss)	$	5,076,144	$	-2,953,211	$	-416,878	$	2,383,547
	Net income (loss) per share	$	2.05	$	-2.07	$	-0.3	$	1.41

FAIR_VALUE_OF_FINANCIAL_INSTRU

FAIR VALUE OF FINANCIAL INSTRUMENTS

12 Months Ended

Dec. 31, 2014

Fair Value Of Financial Instruments [Abstract]

Fair Value of Financial Instruments

NOTE 8 - FAIR VALUE OF FINANCIAL INSTRUMENTS

UNL values its investments in accordance with Accounting Standards Codification 820 – Fair Value Measurements and Disclosures (“ASC 820”). ASC 820 defines fair value, establishes a framework for measuring fair value in generally accepted accounting principles, and expands disclosures about fair value measurement. The changes to past practice resulting from the application of ASC 820 relate to the definition of fair value, the methods used to measure fair value, and the expanded disclosures about fair value measurement. ASC 820 establishes a fair value hierarchy that distinguishes between: (1) market participant assumptions developed based on market data obtained from sources independent of UNL (observable inputs) and (2) UNL’s own assumptions about market participant assumptions developed based on the best information available under the circumstances (unobservable inputs). The three levels defined by the ASC 820 hierarchy are as follows:

Level I – Quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date.

Level II – Inputs other than quoted prices included within Level I that are observable for the asset or liability, either directly or indirectly. Level II assets include the following: quoted prices for  similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the asset or liability, and inputs that are derived principally from or corroborated by observable market data by correlation or other means (market-corroborated inputs).

Level III – Unobservable pricing input at the measurement date for the asset or liability. Unobservable inputs shall be used to measure fair value to the extent that observable inputs are not available.

In some instances, the inputs used to measure fair value might fall within different levels of the fair value hierarchy. The level in the fair value hierarchy within which the fair value measurement in its entirety falls shall be determined based on the lowest input level that is significant to the fair value measurement in its entirety.

The following table summarizes the valuation of UNL’s securities at December 31, 2014 using the fair value hierarchy:

At December 31, 2014

Total

Level I

Level II

Level III

Short-Term Investments

$

12,510,147

$

12,510,147

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

-4,919,890

-4,919,890

—

—

During the year ended December 31, 2014, there were no transfers between Level I and Level II.

The following table summarizes the valuation of UNL’s securities at December 31, 2013 using the fair value hierarchy:

At December 31, 2013

Total

Level I

Level II

Level III

Short-Term Investments

$

22,522,078

$

22,522,078

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

1,090,050

1,090,050

—

—

During the year ended December 31, 2013, there were no transfers between Level I and Level II.

Effective January 1, 2009, UNL adopted the provisions of Accounting Standards Codification 815 – Derivatives and Hedging (“ASC 815”), which require presentation of qualitative disclosures about objectives and strategies for using derivatives, quantitative disclosures about fair value amounts and gains and losses on derivatives.

Fair Value of Derivative Instruments

Derivatives not Accounted

Statements of

Fair Value At

Fair Value At

for as Hedging Instruments

Financial Condition

December 31, 2014

December 31, 2013

Location

Futures - Commodity Contracts

Assets

$

-4,919,890

$

1,090,050

The Effect of Derivative Instruments on the Statements of Operations

For the year ended

For the year ended

For the year ended

December 31, 2014

December 31, 2013

December 31, 2012

Derivatives not Accounted

Location of

Realized

Change in

Realized

Change in

Realized

Change in

for as Hedging Instruments

Gain (Loss)

Gain

Unrealized

Gain

Unrealized

Gain

Unrealized

on Derivatives

(Loss) on

Gain

(Loss) on

Gain

(Loss) on

Gain

Recognized

Derivatives

(Loss) on

Derivatives

(Loss) on

Derivatives

(Loss) on

in Income

Recognized

Derivatives

Recognized

Derivatives

Recognized

Derivatives

in Income

Recognized

in Income

Recognized

in Income

Recognized

in Income

in Income

in Income

Futures -

Realized gain

$

2,205,950

$

2,395,300

$

-12,161,650

Commodity Contracts

(loss) on closed

positions

Change in

-6,009,940

$

1,996,630

$

7,676,740

unrealized

gain (loss) on

open positions

RECENT_ACCOUNTING_PRONOUNCEMEN

RECENT ACCOUNTING PRONOUNCEMENTS	12 Months Ended
	Dec. 31, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	NOTE 9 - RECENT ACCOUNTING PRONOUNCEMENTS
	In December 2011, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2011-11, “Balance Sheet (Topic 210): Disclosures about Offsetting Assets and Liabilities.” The amendments in ASU No. 2011-11 require an entity to disclose information about offsetting and related arrangements to enable users of its financial statements to understand the effect of those arrangements on its financial position. ASU No. 2011-11 is effective for annual reporting periods beginning on or after January 1, 2013, and interim periods within those annual periods.

SUBSEQUENT_EVENTS

SUBSEQUENT EVENTS	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	NOTE 10 - SUBSEQUENT EVENTS
	UNL has performed an evaluation of subsequent events through the date the financial statements were issued. This evaluation did not result in any subsequent events that necessitated disclosures and/or adjustments other than noted below:
	On January 14, 2015, Mr. Howard Mah, Management Director, Chief Financial Officer (Principal Accounting Officer), Secretary and Treasurer of USCF, general partner of United States 12 Month Natural Gas Fund, LP, tendered his resignation effective as soon as the Board of Directors of USCF accepts and appoints a suitable replacement, but no later than the close of business July 15, 2015. In order to ensure an orderly transition, Mr. Mah will remain as the Management Director and Chief Financial Officer (Principal Accounting Officer) of USCF until such time.
	On January 26, 2015, Mr. Nicholas D. Gerber was appointed Chief Executive Officer, President and Secretary of Concierge Technologies, Inc. (“Concierge”), a supplier of mobile video recording devices through its wholly owned subsidiary Janus Cam. Concierge is not affiliated with USCF and the Related Public Funds, other than through ownership by common control. Concierge is a publicly traded company under the ticker symbol “CNCG.”

SUMMARY_OF_SIGNIFICANT_ACCOUNT1

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2014
Summary Of Significant Accounting Policies [Abstract]
Revenue Recognition	Revenue Recognition
	Commodity futures contracts, forward contracts, physical commodities and related options are recorded on the trade date. All such transactions are recorded on the identified cost basis and marked to market daily. Unrealized gains or losses on open contracts are reflected in the statements of financial condition and represent the difference between the original contract amount and the market value (as determined by exchange settlement prices for futures contracts and related options and cash dealer prices at a predetermined time for forward contracts, physical commodities, and their related options) as of the last business day of the year or as of the last date of the financial statements. Changes in the unrealized gains or losses between periods are reflected in the statements of operations. UNL earns interest on its assets denominated in U.S. dollars on deposit with the futures commission merchant (“FCM”) at the overnight Federal Funds Rate less 32 basis points. In addition, UNL earns income on funds held at the custodian or FCM at prevailing market rates earned on such investments.
Brokerage Commissions	Brokerage Commissions
	Brokerage commissions on all open commodity futures contracts are accrued on a full-turn basis.
Income Taxes	Income Taxes
	UNL is not subject to federal income taxes; each partner reports his/her allocable share of income, gain, loss deductions or credits on his/her own income tax return.
	In accordance with accounting principles generally accepted in the United States of America (“GAAP”), UNL is required to determine whether a tax position is more likely than not to be sustained upon examination by the applicable taxing authority, including resolution of any tax related appeals or litigation processes, based on the technical merits of the position. UNL files an income tax return in the U.S. federal jurisdiction, and may file income tax returns in various U.S. states. UNL is not subject to income tax return examinations by major taxing authorities for years before 2011. The tax benefit recognized is measured as the largest amount of benefit that has a greater than fifty percent likelihood of being realized upon ultimate settlement. De-recognition of a tax benefit previously recognized results in UNL recording a tax liability that reduces net assets. However, UNL’s conclusions regarding this policy may be subject to review and adjustment at a later date based on factors including, but not limited to, on-going analysis of and changes to tax laws, regulations and interpretations thereof. UNL recognizes interest accrued related to unrecognized tax benefits and penalties related to unrecognized tax benefits in income tax fees payable, if assessed. No interest expense or penalties have been recognized as of and for the year ended December 31, 2014.
Creations and Redemptions	Creations and Redemptions
	Authorized Participants may purchase Creation Baskets or redeem Redemption Baskets only in blocks of 50,000 shares at a price equal to the NAV of the shares calculated shortly after the close of the core trading session on the NYSE Arca on the day the order is placed.
	UNL receives or pays the proceeds from shares sold or redeemed within three business days after the trade date of the purchase or redemption. The amounts due from Authorized Participants are reflected in UNL’s statements of financial condition as receivable for shares sold, and amounts payable to Authorized Participants upon redemption are reflected as payable for shares redeemed.
Partnership Capital and Allocation of Partnership Income and Losses	Partnership Capital and Allocation of Partnership Income and Losses
	Profit or loss shall be allocated among the partners of UNL in proportion to the number of shares each partner holds as of the close of each month. USCF may revise, alter or otherwise modify this method of allocation as described in the LP Agreement.
Calculation of Per Unit Net Asset Value	Calculation of Per Share Net Asset Value (“NAV”)
	UNL’s per share NAV is calculated on each NYSE Arca trading day by taking the current market value of its total assets, subtracting any liabilities and dividing that amount by the total number of shares outstanding. UNL uses the closing price for the contracts on the relevant exchange on that day to determine the value of contracts held on such exchange.
Net Income (Loss) Per Share	Net Income (Loss) Per Share
	Net income (loss) per share is the difference between the per share NAV at the beginning of each period and at the end of each period. The weighted average number of shares outstanding was computed for purposes of disclosing net income (loss) per weighted average share. The weighted average shares are equal to the number of shares outstanding at the end of the period, adjusted proportionately for shares added and redeemed based on the amount of time the shares were outstanding during such period. There were no shares held by USCF at December 31, 2014.
Offering Costs	Offering Costs
	Offering costs incurred in connection with the registration of additional shares after the initial registration of shares are borne by UNL. These costs include registration fees paid to regulatory agencies and all legal, accounting, printing and other expenses associated with such offerings. These costs are accounted for as a deferred charge and thereafter amortized to expense over twelve months on a straight-line basis or a shorter period, if warranted.
Cash Equivalents	Cash Equivalents
	Cash equivalents include money market funds and overnight deposits or time deposits with original maturity dates of six months or less.
Reclassification	Reclassification
	Certain amounts in the accompanying financial statements were reclassified to conform with the current presentation.
Use of Estimates	Use of Estimates
	The preparation of financial statements in conformity with GAAP requires USCF to make estimates and assumptions that affect the reported amount of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of the revenue and expenses during the reporting period. Actual results may differ from those estimates and assumptions.

CONTRACTS_AND_AGREEMENTS_Table

CONTRACTS AND AGREEMENTS (Tables)	12 Months Ended
	Dec. 31, 2014
Contracts and Agreements [Abstract]
Brokerage Commissions	UNL also incurs commissions to brokers for the purchase and sale of Futures Contracts, Other Natural Gas-Related Investments or short term obligations of the United States of two years or less (“Treasuries”).
		For the Year Ended			For the Year Ended			For the Year Ended
		December 31, 2014			December 31, 2013			December 31, 2012
	Total commissions accrued to brokers	$	3,918		$	8,360		$	14,360
	Total commissions as annualized percentage of average total net assets		0.02	%		0.03	%		0.04	%
	Commissions accrued as a result of rebalancing	$	2,126		$	4,484		$	10,995
	Percentage of commissions accrued as a result of rebalancing		54.26	%		53.64	%		76.57	%
	Commissions accrued as a result of creation and redemption activity	$	1,792		$	3,876		$	3,365
	Percentage of commissions accrued as a result of creation and redemption activity		45.74	%		46.36	%		23.43	%

FINANCIAL_HIGHLIGHTS_Tables

FINANCIAL HIGHLIGHTS (Tables)	12 Months Ended
	Dec. 31, 2014
Financial Highlights [Abstract]
Per Unit Performance Data and Other Supplemental Financial Data	The following table presents per share performance data and other supplemental financial data for the years ended December 31, 2014, 2013 and 2012. This information has been derived from information presented in the financial statements.
		Year Ended			Year Ended			Year Ended
		December 31, 2014			December 31, 2013			December 31, 2012
	Per Share Operating Performance:
	Net asset value, beginning of year	$	18.32		$	17.23		$	21.21
	Total income (loss)		-4.33			1.32			-3.78
	Net expenses		-0.3			-0.23			-0.2
	Net increase (decrease) in net asset value		-4.63			1.09			-3.98
	Net asset value, end of year	$	13.69		$	18.32		$	17.23
	Total Return		-25.27	%		6.33	%		-18.76	%
	Ratios to Average Net Assets
	Total income (loss)		-19.76	%		13.23	%		-11.8	%
	Management fees		0.75	%		0.75	%		0.75	%
	Total expenses excluding management fees		0.85	%		0.51	%		0.4	%
	Expenses waived		-0.67	%		-0.3	%		-0.18	%
	Net expenses excluding management fees		0.18	%		0.21	%		0.22	%
	Net income (loss)		-20.7	%		12.27	%		-12.77	%

QUARTERLY_FINANCIAL_DATA_Unaud1

QUARTERLY FINANCIAL DATA (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following summarized (unaudited) quarterly financial information presents the results of operations and other data for the three-month periods ended March 31, June 30, September 30 and December 31, 2014 and 2013.
				Second				Fourth
		First Quarter		Quarter		Third Quarter		Quarter
		2014		2014		2014		2014
	Total income (loss)	$	2,154,963	$	59,752	$	-1,333,315	$	-4,674,704
	Total expenses		96,400		85,090		75,491		50,602
	Expense waivers		-38,045		-40,700		-39,383		-10,778
	Net expenses		58,355		44,390		36,108		39,824
	Net income (loss)	$	2,096,608	$	15,362	$	-1,369,423	$	-4,714,528
	Net income (loss) per share	$	1.31	$	-0.07	$	-1.52	$	-4.35
				Second				Fourth
		First Quarter		Quarter		Third Quarter		Quarter
		2013		2013		2013		2013
	Total income (loss)	$	5,182,801	$	-2,870,767	$	-352,278	$	2,450,824
	Total expenses		121,121		100,767		94,831		104,839
	Expense waivers		-14,464		-18,323		-30,231		-37,562
	Net expenses		106,657		82,444		64,600		67,277
	Net income (loss)	$	5,076,144	$	-2,953,211	$	-416,878	$	2,383,547
	Net income (loss) per share	$	2.05	$	-2.07	$	-0.3	$	1.41

FAIR_VALUE_OF_FINANCIAL_INSTRU1

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Of Financial Instruments [Abstract]

Valuation of Securities Using the Fair Value Hierarchy

The following table summarizes the valuation of UNL’s securities at December 31, 2014 using the fair value hierarchy:

At December 31, 2014

Total

Level I

Level II

Level III

Short-Term Investments

$

12,510,147

$

12,510,147

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

-4,919,890

-4,919,890

—

—

The following table summarizes the valuation of UNL’s securities at December 31, 2013 using the fair value hierarchy:

At December 31, 2013

Total

Level I

Level II

Level III

Short-Term Investments

$

22,522,078

$

22,522,078

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

1,090,050

1,090,050

—

—

Fair Value of Derivative Instruments

Fair Value of Derivative Instruments

Derivatives not Accounted

Statements of

Fair Value At

Fair Value At

for as Hedging Instruments

Financial Condition

December 31, 2014

December 31, 2013

Location

Futures - Commodity Contracts

Assets

$

-4,919,890

$

1,090,050

Effect of Derivative Instruments on the Condensed Statements of Operations

The Effect of Derivative Instruments on the Statements of Operations

For the year ended

For the year ended

For the year ended

December 31, 2014

December 31, 2013

December 31, 2012

Derivatives not Accounted

Location of

Realized

Change in

Realized

Change in

Realized

Change in

for as Hedging Instruments

Gain (Loss)

Gain

Unrealized

Gain

Unrealized

Gain

Unrealized

on Derivatives

(Loss) on

Gain

(Loss) on

Gain

(Loss) on

Gain

Recognized

Derivatives

(Loss) on

Derivatives

(Loss) on

Derivatives

(Loss) on

in Income

Recognized

Derivatives

Recognized

Derivatives

Recognized

Derivatives

in Income

Recognized

in Income

Recognized

in Income

Recognized

in Income

in Income

in Income

Futures -

Realized gain

$

2,205,950

$

2,395,300

$

-12,161,650

Commodity Contracts

(loss) on closed

positions

Change in

-6,009,940

$

1,996,630

$

7,676,740

unrealized

gain (loss) on

open positions

ORGANIZATION_AND_BUSINESS_Addi

ORGANIZATION AND BUSINESS (Additional Information) (Details) (USD $)	1 Months Ended		12 Months Ended
	Nov. 30, 2009	Nov. 18, 2009	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
			Contracts
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets			$350
Number of initially registered units on Form S-1 with the U.S. Securities and Exchange Commission	30,000,000
Net asset value per share		$50	$13.69	$18.32	$17.23	$21.21	$21.21
Number of units issued		200,000
Value of unit issued		10,000,000
Commenced investment operations date	18-Nov-09
Number of registered units			25,600,000
Derivative, Number of Instruments Held			537
Creation Baskets [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of units per basket			50,000
Prior to July 1, 2011 [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets			$1,000

SUMMARY_OF_SIGNIFICANT_ACCOUNT2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Additional Information) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Minimum likelihood of tax benefits being recognized upon ultimate settlement	50.00%
Recognized interest income expense and penalties related to unrecognized tax benefits	$0
Redemption Baskets [Member]
Significant Accounting Policies [Line Items]
Number of units per basket	50,000
Maximum [Member]
Significant Accounting Policies [Line Items]
Cash equivalents maturity period	6 months

FEES_PAID_BY_THE_FUND_AND_RELA1

FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS - (Additional Information) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fees Paid and Related Party Transactions [Line Items]
USCF Management Fee									UNL is contractually obligated to pay USCF a fee, which is paid monthly, that is equal to 0.75% per annum of average daily total net assets.
Estimated directors' fees and expenses									$6,009	$7,620	$5,705
Licensing fee incurred									2,879	5,001	5,674
Estimated investor tax reporting cost									86,000	125,000	75,000
Costs and expenses annual limit for reimbursement									0.15%
Expense waivers	-10,778	-39,383	-40,700	-38,045	-37,562	-30,231	-18,323	-14,464	-128,906	-100,580	-68,503
Licensing Agreements [Member]
Fees Paid and Related Party Transactions [Line Items]
Fee percentage									0.02%
Assets basis for determining fee percentage									on all net assets
UNL [Member] | Related Public Funds [Member]
Fees Paid and Related Party Transactions [Line Items]
Estimated directors' fees and expenses									$567,863	$555,465	$540,586

CONTRACTS_AND_AGREEMENTS_Broke

CONTRACTS AND AGREEMENTS (Brokerage Commissions) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Floor Brokerage Exchange and Clearance Fees	$3,918	$8,360	$14,360
Annualized percentage of average total net assets	0.02%	0.03%	0.04%
Rebalancing Investments Transaction [Member]
Floor Brokerage Exchange and Clearance Fees	2,126	4,484	10,995
Percentage Of Average Daily Net Assets	54.26%	53.64%	76.57%
Creation And Redemption Activity [Member]
Floor Brokerage Exchange and Clearance Fees	$1,792	$3,876	$3,365
Percentage Of Average Daily Net Assets	45.74%	46.36%	23.43%

CONTRACTS_AND_AGREEMENTS_Addit

CONTRACTS AND AGREEMENTS (Additional Information) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Annual Fee for transfer agency services	$20,000
Maximum [Member]
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 [Member]
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 the Related Public Funds' combined net assets [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.06%
first $500 million of the Related Public Funds' combined net assets [Member] | Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	500,000,000
Related Public Funds' combined net assets greater than $500 million but less than $1 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.05%
Related Public Funds' combined net assets greater than $500 million but less than $1 billion [Member] | Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	500,000,000
Related Public Funds' combined net assets exceed $1 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.04%
Related Public Funds' combined net assets exceed $1 billion [Member] | Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	1,000,000,000
Marketing Agreement [Member] | UNL's assets up to $3 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.06%
Base amount for determining fee percentage	3,000,000,000
Marketing Agreement [Member] | UNL's assets in excess of $3 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.04%
Base amount for determining fee percentage	$3,000,000,000
Marketing Agent And Affliate Of Uscf [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Maximum Aggregate Compensation Paid For Distribution Related Services	10.00%

FINANCIAL_INSTRUMENTS_OFFBALAN1

FINANCIAL INSTRUMENTS, OFF-BALANCE SHEET RISKS AND CONTINGENCIES (Additional Information) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Carrying Amounts and Fair Values of Financial Instruments or Liabilities [Line Items]
Cash investments in money market funds	$9,510,692	$19,522,574
Deposits in domestic and foreign financial institutions	$11,127,927	$6,941,097

FINANCIAL_HIGHLIGHTS_Per_Unit_

FINANCIAL HIGHLIGHTS (Per Unit Performance Data and Other Supplemental Financial Data) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2010	Nov. 18, 2009
Per Unit Operating Performance:
Net asset value, beginning of year	$18.32	$17.23	$21.21	$21.21	$50
Total income (loss)	($4.33)	$1.32	($3.78)
Net expenses	($0.30)	($0.23)	($0.20)
Net increase (decrease) in net asset value	($4.63)	$1.09	($3.98)
Net asset value, end of year	$13.69	$18.32	$17.23	$21.21	$50
Total Return	-25.27%	6.33%	-18.76%
Ratios to Average Net Assets
Total income (loss)	-19.76%	13.23%	-11.80%
Management fees	0.75%	0.75%	0.75%
Total expenses excluding management fees	0.85%	0.51%	0.40%
Expenses waived	-0.67%	-0.30%	-0.18%
Net expenses excluding management fees	0.18%	0.21%	0.22%
Net income (loss)	-20.70%	12.27%	-12.77%

QUARTERLY_FINANCIAL_DATA_Unaud2

QUARTERLY FINANCIAL DATA (Unaudited) (Quarterly Financial Information Presents The Results Of Operations) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Total income (loss)	($4,674,704)	($1,333,315)	$59,752	$2,154,963	$2,450,824	($352,278)	($2,870,767)	$5,182,801	($3,793,304)	$4,410,580	($4,462,964)
Total expenses	50,602	75,491	85,090	96,400	104,839	94,831	100,767	121,121	307,583	421,558	434,731
Expense waivers	-10,778	-39,383	-40,700	-38,045	-37,562	-30,231	-18,323	-14,464	-128,906	-100,580	-68,503
Net expenses	39,824	36,108	44,390	58,355	67,277	64,600	82,444	106,657	178,677	320,978	366,228
Net income (loss)	($4,714,528)	($1,369,423)	$15,362	$2,096,608	$2,383,547	($416,878)	($2,953,211)	$5,076,144	($3,971,981)	$4,089,602	($4,829,192)
Net income (loss) per share	($4.35)	($1.52)	($0.07)	$1.31	$1.41	($0.30)	($2.07)	$2.05	($4.63)	$1.09	($3.98)

FAIR_VALUE_OF_FINANCIAL_INSTRU2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Valuation of Securities Using Fair Value Hierarchy) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	($4,919,890)	$1,090,050
Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	12,510,147	22,522,078
Fair Value, Inputs, Level 1 [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	-4,919,890	1,090,050
Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	12,510,147	22,522,078
Fair Value, Inputs, Level 2 [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | United States [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	$0	$0

FAIR_VALUE_OF_FINANCIAL_INSTRU3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Fair Value of Derivative Instruments) (Details) (Commodity Contracts [Member], Futures [Member], Assets [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
Commodity Contracts [Member] | Futures [Member] | Assets [Member]
Derivatives, Fair Value [Line Items]
Derivatives not Accounted for as Hedging Instruments	($4,919,890)	$1,090,050

FAIR_VALUE_OF_FINANCIAL_INSTRU4

FAIR VALUE OF FINANCIAL INSTRUMENTS (Effect of Derivative Instruments on Condensed Statements of Operations) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain or (Loss) on Derivatives Recognized in Income	$2,205,950	$2,395,300	($12,161,650)
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income	-6,009,940	1,996,630	7,676,740
Commodity Contracts [Member] | Futures [Member] | Realized gain on closed positions
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain or (Loss) on Derivatives Recognized in Income	2,205,950	2,395,300	-12,161,650
Commodity Contracts [Member] | Futures [Member] | Change in unrealized gain on open positions
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income	($6,009,940)	$1,996,630	$7,676,740