United States Natural Gas Fund (UNG) 10-K 2 Mar 15 2014 FY Annual report Financial data

Document_And_Entity_Informatio

Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 27, 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	UNG
Entity Registrant Name	United States Natural Gas Fund, LP
Entity Central Index Key	1376227
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		47,466,476
Entity Public Float			$707,655,310

Statements_of_Financial_Condit

Statements of Financial Condition (USD $)	Dec. 31, 2014	Dec. 31, 2013
Assets
Cash and cash equivalents (Notes 2 and 5)	$589,867,333	$792,445,608
Equity in trading accounts:
Cash and cash equivalents	226,160,966	24,147,579
Unrealized gain (loss) on open commodity futures	-167,811,783	-14,033,910
Unrealized gain (loss) on open swap contracts	0	-6,654,820
Receivable for shares sold	3,239,154	159,392,268
Dividends receivable	7,407	8,580
Directors' fees and insurance receivable	17,361	6,459
Prepaid registration fees	650,697	0
ETF transaction fees receivable	0	4,000
Total assets	652,131,135	955,315,764
Liabilities and Partners' Capital
Payable for shares redeemed	0	14,887,362
General Partner management fees payable (Note 3)	364,245	473,547
Professional fees payable	1,312,648	1,454,406
Brokerage commissions payable	72,750	81,750
License fees payable	27,913	36,535
Total liabilities	1,777,556	16,933,600
Commitments and Contingencies (Notes 3, 4 and 5)
Partners' Capital
General Partner	0	0
Limited Partners	650,353,579	938,382,164
Total Partners' Capital	650,353,579	938,382,164
Total liabilities and partners' capital	$652,131,135	$955,315,764
Limited Partners' shares outstanding	44,466,476	45,566,476
Net asset value per share	$14.63	$20.59
Market value per share	$14.77	$20.69

Schedule_of_Investments

Schedule of Investments (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2014
Unrealized Gain on Open Commodity Futures Contracts	($14,033,910)		($167,811,783)
Open Futures Contracts, Long [Member] | United States [Member] | ICE Natural Gas Futures LD1 H February contracts, expiring January [Member]
Number of Contracts	30,865		31,872
Unrealized Gain on Open Commodity Futures Contracts	-6,052,720		-64,631,417
% of Partners' Capital	-0.65%		-9.94%
Open Futures Contracts, Long [Member] | United States [Member] | NYMEX Natural Gas Futures NG February contracts, expiring January [Member]
Number of Contracts	9,496		14,545
Unrealized Gain on Open Commodity Futures Contracts	-6,683,290		-103,180,366
% of Partners' Capital	-0.71%		-15.86%
Open Futures Contracts, Long [Member] | United States [Member] | NYMEX Natural Gas Futures NN February 2014 contracts, expiring January 2014 [Member]
Number of Contracts	9,080
Unrealized Gain on Open Commodity Futures Contracts	-1,297,900
% of Partners' Capital	-0.14%
Open Over-the-Counter Total Return Swap Contracts [Member] | Swap Agreement to Receive Return on the Custom Natural Gas Index (UNG) - Excess Return [Member]
Unrealized Gain on Open Commodity Futures Contracts	-6,654,820
Market Value	-6,654,820
Range of Termination Dates	4/23/14
Collateral Pledged	24,147,579	[1]
Derivative, Notional Amount	120,932,565	[2]
Total Open Futures Contracts [Member] | Open Futures Contracts, Long [Member] | United States [Member]
Number of Contracts	49,441	[3]	46,417	[4]
Unrealized Gain on Open Commodity Futures Contracts	-14,033,910	[3]	-167,811,783	[4]
% of Partners' Capital	-1.50%	[3]	-25.80%	[4]
Cash Equivalents [Member] | United States [Member]
Market Value	742,544,890		520,470,896
% of Partners' Capital	79.13%		80.03%
Cash Equivalents [Member] | United States [Member] | US Treasury Securities [Member]
Market Value	349,930,861		249,965,145
% of Partners' Capital	37.29%		38.44%
Cash Equivalents [Member] | United States [Member] | US Treasury Securities [Member] | US Treasury Bills 0.05%, 2/26/2015 [Member]
Principal Amount			50,000,000
Market Value			49,996,500
% of Partners' Capital			7.69%
Range of Termination Dates			2/26/15
Cash Equivalents [Member] | United States [Member] | US Treasury Securities [Member] | US Treasury Bills 0.04%, 3/26/2015 [Member]
Principal Amount			50,000,000
Market Value			49,995,916
% of Partners' Capital			7.69%
Range of Termination Dates			3/26/15
Cash Equivalents [Member] | United States [Member] | US Treasury Securities [Member] | US Treasury Bills 0.06%, 4/30/2015 [Member]
Principal Amount			150,000,000
Market Value			149,972,729
% of Partners' Capital			23.06%
Range of Termination Dates			4/30/15
Cash Equivalents [Member] | United States [Member] | US Treasury Securities [Member] | US Treasury Bills 0.05%, 2/27/2014 [Member]
Principal Amount	50,000,000
Market Value	49,996,042
% of Partners' Capital	5.33%
Range of Termination Dates	2/27/14
Cash Equivalents [Member] | United States [Member] | US Treasury Securities [Member] | US Treasury Bills 0.07%, 3/27/2014 [Member]
Principal Amount	100,000,000
Market Value	99,983,472
% of Partners' Capital	10.65%
Range of Termination Dates	3/27/14
Cash Equivalents [Member] | United States [Member] | US Treasury Securities [Member] | US Treasury Bills 0.08%, 4/24/2014 [Member]
Principal Amount	200,000,000	[5]
Market Value	199,951,347	[5]
% of Partners' Capital	21.31%	[5]
Range of Termination Dates	4/24/14
Cash Equivalents [Member] | United States [Member] | Money Market Funds [Member]
Market Value	392,614,029		270,505,751
% of Partners' Capital	41.84%		41.59%
Cash Equivalents [Member] | United States [Member] | Money Market Funds [Member] | Fidelity Institutional Government Portfolio - Class I [Member]
Principal Amount	61,608,278
Market Value	61,608,278
% of Partners' Capital	6.56%
Cash Equivalents [Member] | United States [Member] | Money Market Funds [Member] | Goldman Sachs Financial Square Funds - Government Fund - Class FS [Member]
Principal Amount	30,508,087		8,087
Market Value	30,508,087		8,087
% of Partners' Capital	3.25%		0.00%	[6]
Cash Equivalents [Member] | United States [Member] | Money Market Funds [Member] | Morgan Stanley Institutional Liquidity Funds - Government Portfolio [Member]
Principal Amount	200,495,952		200,495,952
Market Value	200,495,952		200,495,952
% of Partners' Capital	21.37%		30.83%
Cash Equivalents [Member] | United States [Member] | Money Market Funds [Member] | Wells Fargo Advantage Government Money Market Fund - Class I [Member]
Principal Amount	100,001,712		70,001,712
Market Value	$100,001,712		$70,001,712
% of Partners' Capital	10.66%		10.76%
[1]	Financial instruments.
[2]	The aggregate notional amount of UNG’s over-the-counter swap transactions represented 12.66% of UNG’s total assets as of December 31, 2013.
[3]	Collateral amounted to $24,147,579 on open future contracts.
[4]	Collateral amounted to $226,156,153 on open future contracts.
[5]	Security or partial security segregated as collateral for open over-the-counter total return swap contracts.
[6]	Represents less than 0.005%.

Schedule_of_Investments_Parent

Schedule of Investments (Parenthetical) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Swap transaction as a percentage of total asset		12.66%
Collateral Amount On Open Futures Contracts	226,156,153	24,147,579
United States [Member] | US Treasury Bills 0.05%, 2/26/2015 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]
Interest rate	0.05%
Expiration date	2/26/15
United States [Member] | US Treasury Bills 0.04%, 3/26/2015 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]
Interest rate	0.04%
Expiration date	3/26/15
United States [Member] | US Treasury Bills 0.06%, 4/30/2015 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]
Interest rate	0.06%
Expiration date	4/30/15
United States [Member] | US Treasury Bills 0.05%, 2/27/2014 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]
Interest rate		0.05%
Expiration date		2/27/14
United States [Member] | US Treasury Bills 0.07%, 3/27/2014 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]
Interest rate		0.07%
Expiration date		3/27/14
United States [Member] | US Treasury Bills 0.08%, 4/24/2014 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]
Interest rate		0.08%
Expiration date		4/24/14

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 contracts:
Realized gain (loss) on closed futures contracts	($47,954,734)	$155,734,315	($243,672,550)
Realized gain (loss) on closed swap contracts	25,690,444	13,643,971	-75,525,786
Change in unrealized gain (loss) on open futures contracts	-153,777,873	562,933	34,395,462
Change in unrealized gain (loss) on open swap contracts	6,654,820	-3,183,881	9,334,753
Dividend income	88,541	126,075	131,491
Interest income	186,989	200,251	237,662
ETF transaction fees	235,000	224,000	216,000
Total income (loss)	-168,876,813	167,307,664	-274,882,968
Expenses
General Partner management fees (Note 3)	4,336,707	5,737,913	6,154,688
Professional fees	1,395,991	1,725,246	1,318,461
Brokerage commissions	2,001,949	2,400,039	3,499,652
Directors' fees and insurance	191,887	199,863	172,837
License fees	108,418	143,884	156,103
Registration fees	238,716	850	-18,588
Total expenses	8,273,668	10,207,795	11,283,153
Net income (loss)	($177,150,481)	$157,099,869	($286,166,121)
Net income (loss) per limited partnership share	($5.96)	$1.72	($7.01)
Net income (loss) per weighted average limited partnership share	($5.51)	$3.21	($5.39)
Weighted average limited partnership shares outstanding	32,150,038	48,892,503	53,045,948

Statements_of_Changes_in_Partn

Statements of Changes in Partners' Capital (USD $)		Total	General Partner [Member]	Limited Partners [Member]
Balances at Dec. 31, 2011		$1,072,096,173	$0	$1,072,096,173
Net asset value, beginning of year at Dec. 31, 2011	[1]	$25.88
Addition of partnership shares	[2]	2,558,402,142	0	2,558,402,142
Redemption of partnership shares	[2]	-2,158,059,538	0	-2,158,059,538
Net income		-286,166,121	0	-286,166,121
Balances at Dec. 31, 2012		1,186,272,656	0	1,186,272,656
Net asset value, end of year at Dec. 31, 2012		$18.87
Addition of partnership shares		2,206,756,302	0	2,206,756,302
Redemption of partnership shares		-2,611,746,663	0	-2,611,746,663
Net income		157,099,869	0	157,099,869
Balances at Dec. 31, 2013		938,382,164	0	938,382,164
Net asset value, end of year at Dec. 31, 2013		$20.59
Addition of partnership shares		3,030,504,891	0	3,030,504,891
Redemption of partnership shares		-3,141,382,995	0	-3,141,382,995
Net income		-177,150,481	0	-177,150,481
Balances at Dec. 31, 2014		$650,353,579	$0	$650,353,579
Net asset value, end of year at Dec. 31, 2014		$14.63
[1]	On February 21, 2012, there was a 4-for-1 reverse share split. The Financial Highlights have been adjusted for the periods shown to reflect the 4-for-1 reverse share split on a retroactive basis.
[2]	On February 21, 2012, there was a 4-for-1 reverse share split. The Statements of Changes in Partners’ Capital have been adjusted for the period shown to reflect the 4-for-1 reverse share split on a retroactive basis.

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 units	133,400,000	112,900,000	134,625,000
Redemption of partnership units	134,500,000	130,200,000	113,157,981

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)	($177,150,481)	$157,099,869	($286,166,121)
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	-202,013,387	120,655,920	61,824,405
Unrealized (gain) loss on open futures contracts	153,777,873	-562,933	-34,395,462
Unrealized (gain) loss on open swap contracts	-6,654,820	3,183,881	-9,334,753
(Increase) decrease in dividends receivable	1,173	7,776	-7,490
(Increase) decrease in interest receivable	0	0	174
(Increase) decrease in directors' fees and insurance receivable	-10,902	-4,908	7,562
(Increase) decrease in prepaid registration fees	-650,697	0	0
(Increase) decrease in ETF transaction fees receivable	4,000	-2,000	-1,000
Increase (decrease) in investment payable	0	0	-772
Increase (decrease) in General Partner management fees payable	-109,302	-111,873	-14,103
Increase (decrease) in professional fees payable	-141,758	-148,477	-461,654
Increase (decrease) in brokerage commissions payable	-9,000	-40,500	-44,000
Increase (decrease) in license fees payable	-8,622	-9,665	-11,289
Increase (decrease) in registration fees payable	0	-153	-19,388
Net cash provided by (used in) operating activities	-232,965,923	280,066,937	-268,623,891
Cash Flows from Financing Activities:
Addition of partnership shares	3,186,658,005	2,066,371,800	2,539,394,376
Redemption of partnership shares	-3,156,270,357	-2,654,503,851	-2,108,938,724
Net cash provided by (used in) financing activities	30,387,648	-588,132,051	430,455,652
Net Increase (Decrease) in Cash and Cash Equivalents	-202,578,275	-308,065,114	161,831,761
Cash and Cash Equivalents, beginning of year	792,445,608	1,100,510,722	938,678,961
Cash and Cash Equivalents, end of year	$589,867,333	$792,445,608	$1,100,510,722

Organization_and_Business

Organization and Business	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Business	NOTE 1 - ORGANIZATION AND BUSINESS
	The United States Natural Gas Fund, LP (“UNG”) was organized as a limited partnership under the laws of the state of Delaware on September 11, 2006. UNG is a commodity pool that issues limited partnership shares (“shares”) that may be purchased and sold on the NYSE Arca, Inc. (the “NYSE Arca”). Prior to November 25, 2008, UNG’s shares traded on the American Stock Exchange (the “AMEX”). UNG will continue in perpetuity, unless terminated sooner upon the occurrence of one or more events as described in its Fourth Amended and Restated Agreement of Limited Partnership dated as of March 1, 2013 (the “LP Agreement”). The investment objective of UNG 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 price of the futures contract on natural gas traded on the New York Mercantile Exchange (the “NYMEX”) that is the near month contract to expire, except when the near month contract is within two weeks of expiration, in which case the futures contract will be the next month contract to expire (the “Benchmark Futures Contract”), less UNG’s expenses. It is not the intent of UNG 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 UNG 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 UNG, 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). UNG 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, UNG held 14,545 NG Futures Contracts traded on the NYMEX, 31,872 Natural Gas Futures LD1 Contracts traded on the ICE Futures and over-the-counter swap transactions with one counterparty, JP Morgan Chase Bank, NA. The over-the-counter swap transaction with JP Morgan Chase Bank, NA was terminated effective April 23, 2014.
	UNG commenced investment operations on April 18, 2007 and has a fiscal year ending on December 31. USCF is responsible for the management of UNG. 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 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, “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 AMEX by NYSE Euronext, each of USO’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”), the United States 12 Month Natural Gas Fund, LP (“UNL”) 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, “UNL” on November 18, 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 (the “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. On January 30, 2015, USCF as the sponsor of 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.
	All funds listed previously are referred to collectively herein as the “Related Public Funds.”
	UNG issues shares to certain authorized purchasers (“Authorized Participants”) by offering baskets consisting of 100,000 shares (“Creation Baskets”) through ALPS Distributors, Inc., as the marketing agent (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.
	In addition, Authorized Participants pay UNG a $1,000 fee for each order placed to create one or more Creation Baskets or to redeem one or more baskets (“Redemption Baskets”), consisting of 100,000 shares. 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 UNG but rather at market prices quoted on such exchange.
	In April 2007, UNG initially registered 30,000,000 shares on Form S-1 with the U.S. Securities and Exchange Commission (the “SEC”). On April 18, 2007, UNG listed its shares on the AMEX under the ticker symbol “UNG”. On that day, UNG established its initial per share NAV by setting the price at $50.00 per share and issued 200,000 shares in exchange for $10,001,000. UNG also commenced investment operations on April 18, 2007 by purchasing Futures Contracts traded on the NYMEX based on natural gas. As of December 31, 2014, UNG had registered a total of 1,680,000,000 shares.
	On February 21, 2012, after the close of trading on the NYSE Arca, UNG effected a 4-for-1 reverse share split and post-split shares of UNG began trading on February 22, 2012. As a result of the reverse share split, every four pre-split shares of UNG were automatically exchanged for one post-split share. Immediately prior to the reverse split, there were 174,297,828 shares of UNG issued and outstanding, representing a per share NAV of $5.51. Immediately after the reverse share split, the number of issued and outstanding shares of UNG decreased to 43,574,457, not accounting for fractional shares, and the per share NAV increased to $22.04. In connection with the reverse share split, the CUSIP number of UNG’s shares changed to 912318201. UNG’s ticker symbol, “UNG,” remains the same.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
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. UNG earns interest on its assets denominated in U.S. dollars on deposit with the FCM at the overnight Federal Funds Rate less 32 basis points. In addition, UNG earns income on funds held at the custodian or FCM at prevailing market rates earned on such investments.
	Investments in over-the-counter swap contracts (see Note 5) are arrangements to exchange a periodic payment for a market-linked return, each based on a notional amount. To the extent that the total return of the security or index underlying the transaction exceeds or falls short of the offsetting periodic payment obligation, UNG receives a payment from, or makes a payment to, the swap counterparty. The over-the-counter swap contracts are valued daily based upon the appreciation or depreciation of the underlying securities subsequent to the effective date of the contract. Changes in the value of the swaps are reported as unrealized gains and losses and periodic payments are recorded as realized gains or losses in the accompanying statements of operations.
	Brokerage Commissions
	Brokerage commissions on all open commodity futures contracts are accrued on a full-turn basis.
	Swap Premiums
	Upfront fees paid by UNG for over-the-counter swap contracts are reflected on the statements of financial condition and represent payments made upon entering into a swap agreement to compensate for differences between the stated terms of the agreement and prevailing market conditions. The fees are amortized daily over the term of the swap agreement.
	Income Taxes
	UNG 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”), UNG 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. UNG files an income tax return in the U.S. federal jurisdiction, and may file income tax returns in various U.S. states. UNG 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 UNG recording a tax liability that reduces net assets. However, UNG’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. UNG 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 100,000 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.
	UNG 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 UNG’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 UNG 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”)
	UNG’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. UNG 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 UNG. 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 to 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.
	Other
	On February 21, 2012, after the close of the NYSE Arca, UNG effected a 4-for-1 reverse share split and post-split shares of UNG began trading on February 22, 2012. The audited financial statements in this annual report on Form 10-K are presented in accordance with Accounting Standards Codification 260 for purposes of presenting the 4-for-1 reverse split on a historical basis for all periods reported.

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 UNG in accordance with the objectives and policies of UNG. In addition, USCF has arranged for one or more third parties to provide administrative, custody, accounting, transfer agency and other necessary services to UNG. For these services, UNG is contractually obligated to pay USCF a fee, which is paid monthly, that is equal to 0.60% per annum of average daily total net assets of $1,000,000,000 or less and 0.50% per annum of average daily total net assets that are greater than $1,000,000,000.
	Ongoing Registration Fees and Other Offering Expenses
	UNG 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, UNG incurred $238,716, $850 and $(18,588), respectively, in registration fees and other offering expenses.
	Directors’ Fees and Expenses
	UNG is responsible for paying its portion of the directors’ and officers’ liability insurance for UNG and the Related Public Funds and the fees and expenses of the independent directors who also serve as audit committee members of UNG and the Related Public Funds organized as limited partnerships and, as of July 8, 2011, the Related Public Funds organized as a series of a Delaware statutory trust. UNG 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 UNG and the Related Public Funds. UNG’s portion of such fees and expenses for the year ended December 31, 2014 was $191,887. For the year ended December 31, 2013, these fees and expenses were $555,465 for UNG and the Related Public Funds. UNG’s portion of such fees and expenses for the year ended December 31, 2013 was $199,863. For the year ended December 31, 2012, these fees and expenses $540,586 for UNG and the Related Public Funds. UNG’s portion of such fees and expenses for the year ended December 31, 2012 was $172,837. Effective as of April 1, 2010, UNG also became responsible for paying its portion of any payments that may become due to the independent directors pursuant to the deferred compensation agreements entered into between the independent directors, USCF, UNG and the Related Public Funds, except USCI, USAG, CPER and USMI.
	Licensing Fees
	As discussed in Note 4 below, UNG entered into a licensing agreement with the NYMEX on April 10, 2006, as amended on October 20, 2011. Pursuant to the agreement, through October 19, 2011, UNG and the Related Public Funds, other than BNO, USCI, CPER, USAG and USMI, paid a licensing fee that was equal to 0.04% for the first $1,000,000,000 of combined net assets of the funds and 0.02% for combined net assets above $1,000,000,000. On and after October 20, 2011, UNG 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, UNG incurred $108,418, $143,884 and $156,103, respectively, under this arrangement.
	Investor Tax Reporting Cost
	The fees and expenses associated with UNG’s audit expenses and tax accounting and reporting requirements are paid by UNG. These costs were approximately $1,385,000, $1,700,000, and $1,900,000 for the years ended December 31, 2014, 2013 and 2012.
	Other Expenses and Fees
	In addition to the fees described above, UNG pays all brokerage fees, transaction costs for over-the-counter swaps, taxes and other expenses in connection with the operation of UNG, excluding costs and expenses paid by USCF as outlined in “Note 4- Contracts and Agreements” below.

Contracts_and_Agreements

Contracts and Agreements	12 Months Ended
	Dec. 31, 2014
Contractors [Abstract]
Contracts and Agreements	NOTE 4 - CONTRACTS AND AGREEMENTS
	UNG is party to a marketing agent agreement, dated as of April 17, 2007, as amended from time to time, with the Marketing Agent and USCF, whereby the Marketing Agent provides certain marketing services for UNG as outlined in the agreement. The fees of the Marketing Agent, which are borne by USCF, are equal to 0.06% on UNG’s assets up to $3 billion and 0.04% on UNG’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 10% of the gross proceeds of UNG’s offering.
	The above fees do not include website construction and development, which are also borne by USCF.
	UNG is also party to a custodian agreement, dated March 5, 2007, as amended from time to time, with Brown Brothers Harriman & Co. (“BBH&Co.”) and USCF, whereby BBH&Co. holds investments on behalf of UNG. USCF pays the fees of the custodian, which are determined by the parties from time to time. In addition, UNG is party to an administrative agency agreement, dated March 5, 2007, as amended from time to time, with USCF and BBH&Co., whereby BBH&Co. acts as the administrative agent, transfer agent and registrar for UNG. 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 UNG 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, UNG entered into a brokerage agreement with RBC Capital Markets, LLC (“RBC Capital” or “RBC”) to serve as UNG’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 UNG 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 UNG’s account. In accordance with each agreement, RBC Capital and UBS Securities charge UNG 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 UNG issues shares as a result of a Creation Basket, as well as fees incurred when selling Futures Contracts and options on Futures Contracts when UNG 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. UNG 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	$	2,010,949		$	2,400,039		$	3,499,652
	Commissions accrued as a result of rebalancing	$	1,623,581		$	2,036,257		$	2,954,424
	Percentage of commissions accrued as a result of rebalancing		81.1	%		84.84	%		84.42	%
	Commissions accrued as a result of creation and redemption activity	$	378,368		$	363,782		$	545,228
	Percentage of commissions accrued as a result of creation and redemption activity		18.9	%		15.16	%		15.58	%
	The decrease in the total commissions accrued to brokers for the year ended December 31, 2014 as compared to the year ended December 31, 2013 was primarily the result of decreased brokerage fees due to a lower number of Natural Gas Interests being held and traded. The decrease in the total commissions accrued to brokers for the year ended December 31, 2013 as compared to the year ended December 31, 2012, was the result of two factors: i) decreased brokerage fees due to a lower number of Natural Gas Interests being held and traded and ii) a reduction in average commission rates during the year ended December 31, 2013. As an annualized percentage of average daily total net assets, the figure for the year ended December 31, 2014 represents approximately 0.28% of average daily total net assets. By comparison, the figure for the year ended December 31, 2013 represents approximately 0.25% of average daily total net assets and the figure for the year ended December 31, 2012 represented approximately 0.33% of average daily 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.
	UNG and the NYMEX entered into a licensing agreement on April 10, 2006, as amended on October 20, 2011, whereby UNG was granted a non-exclusive license to use certain of the NYMEX’s settlement prices and service marks. Under the licensing agreement, UNG 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. UNG expressly disclaims any association with the NYMEX or endorsement of UNG 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
	UNG engages in the trading of futures contracts, options on futures contracts, cleared swaps and over-the-counter swaps (collectively, “derivatives”). UNG 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.
	UNG may enter into futures contracts, options on futures contracts, cleared swaps and over-the-counter swaps 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, e.g., ICE Clear Europe., but which 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 it with a cleared swap. Cleared swaps are intended to provide the efficiencies and benefits that centralized clearing on 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 UNG 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 UNG were exchange-traded futures contracts, cleared swaps or fully-collateralized over-the-counter swaps through December 31, 2014. The liquidity and credit risks associated with exchange-traded contracts and cleared swaps are generally perceived to be less than those associated with over-the-counter swap transactions since, in over-the-counter swap transactions, a party must rely solely on the credit of its respective individual counterparties. As of December 31, 2014, UNG maintained no over-the-counter swap transactions. The over-the-counter swap transaction with JPMorgan Chase Bank, NA was terminated effective April 23, 2014. Over-the counter swap transactions subject UNG 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. UNG 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. However, as compared to its over-the-counter swap transactions, it may more easily realize value by reselling its futures contracts. In addition, UNG bears the risk of financial failure by the clearing broker.
	At December 31, 2014, UNG’s counterparties posted $0 in cash and $0 in securities as collateral with UNG’s custodian, as compared with $0 in cash and $0 in securities for the year ended December 31, 2013. Under these agreements, UNG posted collateral with respect to its obligations of $0 in cash and $0 in securities, such as Treasuries, at December 31, 2014, as compared with $0 in cash and $19,477,185 in securities at December 31, 2013.
	UNG’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 UNG’s assets posted with that FCM; however, the majority of UNG’s assets are held in Treasuries, cash and/or cash equivalents with UNG’s custodian and would not be impacted by the insolvency of a FCM. The failure or insolvency of UNG’s custodian, however, could result in a substantial loss of UNG’s assets.
	USCF invests a portion of UNG’s cash in money market funds that seek to maintain a stable per share NAV. UNG 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, UNG held investments in money market funds in the amounts of $270,505,751 and $392,614,029, respectively. UNG 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, UNG held cash deposits and investments in Treasuries in the amounts of $545,522,548 and $423,979,158, respectively, with the custodian and FCM. Some or all of these amounts may be subject to loss should UNG’s custodian and/or FCM cease operations.
	For derivatives, risks arise from changes in the market value of the contracts. Theoretically, UNG 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, UNG 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.
	UNG’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, UNG 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 UNG 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,			December  31,			December  31,
			2014			2013			2012
	Per Share Operating Performance:
	Net asset value, beginning of year		$	20.59		$	18.87		$	25.88	*
	Total income (loss)			-5.7			1.93			-6.8
	Net expenses			-0.26			-0.21			-0.21
	Net increase (decrease) in net asset value			-5.96			1.72			-7.01
	Net asset value, end of year		$	14.63		$	20.59		$	18.87
	Total Return			-28.95	%		9.11	%		-27.09	%
	Ratios to Average Net Assets
	Total income (loss)			-23.36	%		17.44	%		-26.42	%
	Expenses excluding management fees			0.54	%		0.47	%		0.49	%
	Management fees			0.6	%		0.6	%		0.59	%
	Net income (loss)			-24.51	%		16.38	%		-27.5	%
		*	On February 21, 2012, there was a 4-for-1 reverse share split. The Financial Highlights have been adjusted for the periods shown to reflect the 4-for-1 reverse share split on a retroactive basis.
	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 UNG.

Quarterly_Financial_Data_Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	NOTE 7 - QUARTERLY FINANCIAL DATA (Unaudited)
	The following summarized (unaudited) quarterly financial information presents the results of operations and other data for three-month periods ended March 31, June 30, September 30 and December 31, 2014 and 2013.
		First		Second		Third		Fourth
		Quarter		Quarter		Quarter		Quarter
		2014		2014		2014		2014
	Total income (loss)	$	155,083,163	$	15,991,068	$	-64,717,705	$	-275,233,339
	Total expenses		2,262,092		2,069,407		2,049,423		1,892,746
	Net income (loss)	$	152,821,071	$	13,921,661	$	-66,767,128	$	-277,126,085
	Net income (loss) per share	$	3.76	$	0.23	$	-2.48	$	-7.47
		First		Second		Third		Fourth
		Quarter		Quarter		Quarter		Quarter
		2013		2013		2013		2013
	Total income (loss)	$	166,838,065	$	-117,977,008	$	-13,383,047	$	131,829,654
	Total expenses		2,717,110		2,473,605		2,510,685		2,506,395
	Net income (loss)	$	164,120,955	$	-120,450,613	$	-15,893,732	$	129,323,259
	Net income (loss) per share	$	3.06	$	-3.04	$	-0.59	$	2.29

Fair_Value_Of_Financial_Instru

Fair Value Of Financial Instruments

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Fair Value Of Financial Instruments

NOTE 8 - FAIR VALUE OF FINANCIAL INSTRUMENTS

UNG 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 UNG (observable inputs) and (2) UNG’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 UNG’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

$

520,470,896

$

520,470,896

$

–

$

–

Exchange-Traded Futures Contracts

-167,811,783

$

-167,811,783

–

–

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

Following is a reconciliation of assets in which significant observable inputs (Level 3) were used in determining fair value as of December 31, 2014:

Total Return Swap Contracts

Beginning balance as of 12/31/13

$

-6,654,820

Realized gain (loss)*

—

Change in unrealized gain (loss)

6,654,820

Ending balance as of 12/31/14

$

—

*

The realized gain (loss) incurred during the fiscal year ended December 31, 2014 for total return swaps was $25,690,444.

The following table summarizes the valuation of UNG’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

$

742,544,890

$

742,544,890

$

–

$

–

Exchange-Traded Futures Contracts

-14,033,910

-14,033,910

–

–

Exchange-Traded Cleared Swap Contracts

–

–

–

–

Over-the-Counter Total Return Swap Transactions

-6,654,820

–

–

-6,654,820

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

Following is a reconciliation of assets in which significant observable inputs (Level 3) were used in determining fair value as of December 31, 2013:

Total Return Swap Contracts

Beginning balance as of 12/31/12

$

-3,470,939

Realized gain (loss)*

–

Change in unrealized gain (loss)

-3,183,881

Ending balance as of 12/31/13

$

-6,654,820

*

The realized loss incurred during the fiscal year ended December 31, 2013 for total return swaps was $13,643,971.

Effective January 1, 2009, UNG adopted the provisions of Accounting Standards Codification 815—Derivatives and Hedging, 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

Statements of

Accounted

Financial

Fair Value

Fair Value

for as Hedging

Condition

At

At

Instruments

Location

December 31, 2014

December 31, 2013

Futures –Commodity Contracts

Assets

$

-167,811,783

$

-14,033,910

Swaps - Commodity Contracts

Assets

—

-6,654,820

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

Change in

Change in

Change in

Location of

Realized Gain

Unrealized

Realized Gain

Unrealized

Realized Gain

Unrealized

Gain

(Loss) on

Gain

(Loss) on

Gain

(Loss) on

Gain

Derivatives

(Loss) on

Derivatives

(Loss) on

Derivatives

(Loss) on

Derivatives

(Loss) on

not Accounted

Derivatives

Recognized

Derivatives

Recognized

Derivatives

Recognized

Derivatives

for as Hedging

Recognized

in

Recognized

in

Recognized

in

Recognized

Instruments

in Income

Income

in Income

Income

in Income

Income

in Income

Futures – Commodity Contracts

Realized gain (loss) on closed futures positions

$

-47,954,734

$

155,734,315

$

-243,672,550

Change in unrealized gain (loss) on open futures positions

$

-153,777,873

$

562,933

$

34,395,462

Swaps – Commodity Contracts

Realized gain (loss) on closed swap contracts

$

25,690,444

13,643,971

$

-75,525,786

Change in unrealized gain (loss) on open swap contracts

$

6,654,820

$

-3,183,881

$

9,334,753

Recent_Accounting_Pronouncemen

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2014
Accounting Changes and Error Corrections [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
	UNG 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 United States Commodity Funds LLC, general partner of United States 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 “CNGC.”

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
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. UNG earns interest on its assets denominated in U.S. dollars on deposit with the FCM at the overnight Federal Funds Rate less 32 basis points. In addition, UNG earns income on funds held at the custodian or FCM at prevailing market rates earned on such investments.
	Investments in over-the-counter swap contracts (see Note 5) are arrangements to exchange a periodic payment for a market-linked return, each based on a notional amount. To the extent that the total return of the security or index underlying the transaction exceeds or falls short of the offsetting periodic payment obligation, UNG receives a payment from, or makes a payment to, the swap counterparty. The over-the-counter swap contracts are valued daily based upon the appreciation or depreciation of the underlying securities subsequent to the effective date of the contract. Changes in the value of the swaps are reported as unrealized gains and losses and periodic payments are recorded as realized gains or losses in the accompanying statements of operations.
Brokerage Commissions	Brokerage Commissions
	Brokerage commissions on all open commodity futures contracts are accrued on a full-turn basis.
Swap Premiums	Swap Premiums
	Upfront fees paid by UNG for over-the-counter swap contracts are reflected on the statements of financial condition and represent payments made upon entering into a swap agreement to compensate for differences between the stated terms of the agreement and prevailing market conditions. The fees are amortized daily over the term of the swap agreement
Income Taxes	Income Taxes
	UNG 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”), UNG 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. UNG files an income tax return in the U.S. federal jurisdiction, and may file income tax returns in various U.S. states. UNG 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 UNG recording a tax liability that reduces net assets. However, UNG’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. UNG 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 100,000 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.
	UNG 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 UNG’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 UNG 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”)
	UNG’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. UNG 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 UNG. 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 to 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.
Other	Other
	On February 21, 2012, after the close of the NYSE Arca, UNG effected a 4-for-1 reverse share split and post-split shares of UNG began trading on February 22, 2012. The audited financial statements in this annual report on Form 10-K are presented in accordance with Accounting Standards Codification 260 for purposes of presenting the 4-for-1 reverse split on a historical basis for all periods reported.

Contracts_and_Agreements_Table

Contracts and Agreements (Tables)	12 Months Ended
	Dec. 31, 2014
Contractors [Abstract]
Brokerage Commissions		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	$	2,010,949		$	2,400,039		$	3,499,652
	Commissions accrued as a result of rebalancing	$	1,623,581		$	2,036,257		$	2,954,424
	Percentage of commissions accrued as a result of rebalancing		81.1	%		84.84	%		84.42	%
	Commissions accrued as a result of creation and redemption activity	$	378,368		$	363,782		$	545,228
	Percentage of commissions accrued as a result of creation and redemption activity		18.9	%		15.16	%		15.58	%

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,			December  31,			December  31,
			2014			2013			2012
	Per Share Operating Performance:
	Net asset value, beginning of year		$	20.59		$	18.87		$	25.88	*
	Total income (loss)			-5.7			1.93			-6.8
	Net expenses			-0.26			-0.21			-0.21
	Net increase (decrease) in net asset value			-5.96			1.72			-7.01
	Net asset value, end of year		$	14.63		$	20.59		$	18.87
	Total Return			-28.95	%		9.11	%		-27.09	%
	Ratios to Average Net Assets
	Total income (loss)			-23.36	%		17.44	%		-26.42	%
	Expenses excluding management fees			0.54	%		0.47	%		0.49	%
	Management fees			0.6	%		0.6	%		0.59	%
	Net income (loss)			-24.51	%		16.38	%		-27.5	%
		*	On February 21, 2012, there was a 4-for-1 reverse share split. The Financial Highlights have been adjusted for the periods shown to reflect the 4-for-1 reverse share split on a retroactive basis.

Quarterly_Financial_Data_Unaud1

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	The following summarized (unaudited) quarterly financial information presents the results of operations and other data for three-month periods ended March 31, June 30, September 30 and December 31, 2014 and 2013.
		First		Second		Third		Fourth
		Quarter		Quarter		Quarter		Quarter
		2014		2014		2014		2014
	Total income (loss)	$	155,083,163	$	15,991,068	$	-64,717,705	$	-275,233,339
	Total expenses		2,262,092		2,069,407		2,049,423		1,892,746
	Net income (loss)	$	152,821,071	$	13,921,661	$	-66,767,128	$	-277,126,085
	Net income (loss) per share	$	3.76	$	0.23	$	-2.48	$	-7.47
		First		Second		Third		Fourth
		Quarter		Quarter		Quarter		Quarter
		2013		2013		2013		2013
	Total income (loss)	$	166,838,065	$	-117,977,008	$	-13,383,047	$	131,829,654
	Total expenses		2,717,110		2,473,605		2,510,685		2,506,395
	Net income (loss)	$	164,120,955	$	-120,450,613	$	-15,893,732	$	129,323,259
	Net income (loss) per share	$	3.06	$	-3.04	$	-0.59	$	2.29

Fair_Value_Of_Financial_Instru1

Fair Value Of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2014

Fair Value Disclosures [Abstract]

Valuation of USNG's Securities Using the Fair Value Hierarchy

The following table summarizes the valuation of UNG’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

$

520,470,896

$

520,470,896

$

–

$

–

Exchange-Traded Futures Contracts

-167,811,783

$

-167,811,783

–

–

The following table summarizes the valuation of UNG’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

$

742,544,890

$

742,544,890

$

–

$

–

Exchange-Traded Futures Contracts

-14,033,910

-14,033,910

–

–

Exchange-Traded Cleared Swap Contracts

–

–

–

–

Over-the-Counter Total Return Swap Transactions

-6,654,820

–

–

-6,654,820

Reconciliation of Assets in which Significant Observable Inputs (Level III) were Used in Determining Fair Value

Following is a reconciliation of assets in which significant observable inputs (Level 3) were used in determining fair value as of December 31, 2014:

Total Return Swap Contracts

Beginning balance as of 12/31/13

$

-6,654,820

Realized gain (loss)*

—

Change in unrealized gain (loss)

6,654,820

Ending balance as of 12/31/14

$

—

*

The realized gain (loss) incurred during the fiscal year ended December 31, 2014 for total return swaps was $25,690,444.

Following is a reconciliation of assets in which significant observable inputs (Level 3) were used in determining fair value as of December 31, 2013:

Total Return Swap Contracts

Beginning balance as of 12/31/12

$

-3,470,939

Realized gain (loss)*

–

Change in unrealized gain (loss)

-3,183,881

Ending balance as of 12/31/13

$

-6,654,820

*

The realized loss incurred during the fiscal year ended December 31, 2013 for total return swaps was $13,643,971.

Fair Value of Derrivative Instruments

Fair Value of Derivative Instruments

Derivatives not

Statements of

Accounted

Financial

Fair Value

Fair Value

for as Hedging

Condition

At

At

Instruments

Location

December 31, 2014

December 31, 2013

Futures –Commodity Contracts

Assets

$

-167,811,783

$

-14,033,910

Swaps - Commodity Contracts

Assets

—

-6,654,820

Effect of Derivative Instruments on the 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

Change in

Change in

Change in

Location of

Realized Gain

Unrealized

Realized Gain

Unrealized

Realized Gain

Unrealized

Gain

(Loss) on

Gain

(Loss) on

Gain

(Loss) on

Gain

Derivatives

(Loss) on

Derivatives

(Loss) on

Derivatives

(Loss) on

Derivatives

(Loss) on

not Accounted

Derivatives

Recognized

Derivatives

Recognized

Derivatives

Recognized

Derivatives

for as Hedging

Recognized

in

Recognized

in

Recognized

in

Recognized

Instruments

in Income

Income

in Income

Income

in Income

Income

in Income

Futures – Commodity Contracts

Realized gain (loss) on closed futures positions

$

-47,954,734

$

155,734,315

$

-243,672,550

Change in unrealized gain (loss) on open futures positions

$

-153,777,873

$

562,933

$

34,395,462

Swaps – Commodity Contracts

Realized gain (loss) on closed swap contracts

$

25,690,444

13,643,971

$

-75,525,786

Change in unrealized gain (loss) on open swap contracts

$

6,654,820

$

-3,183,881

$

9,334,753

Organization_and_Business_Addi

Organization and Business (Additional Information) (Details) (USD $)

1 Months Ended

Feb. 21, 2012

Apr. 18, 2007

Apr. 30, 2007

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2010

Share

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

Number of initially registered units on Form S-1 with the U.S. Securities and Exchange Commission

30,000,000

Net Asset Value Per Unit

$50

$14.63

$20.59

$18.87

$25.88

[1]

$25.88

[2]

Number of units issued

200,000

Value of unit issued

$10,001,000

Number of registered units

$1,680,000,000

Committee For Uniform Securities Identification Procedure Cusip

CUSIP number of UNG’s shares changed to 912318201.

Operations Commenced Date

18-Apr-07

Reverse unit split ratio

4

Pre-split units of USNG automatically exchanged for one post-split unit

4

Open Futures Contracts, Long [Member] | United States [Member] | NYMEX Natural Gas Futures NG February 2015 contracts, expiring January 2015 [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Number of Contracts

14,545

9,496

Open Futures Contracts, Long [Member] | United States [Member] | NYMEX Natural Gas Futures NN February 2014 contracts, expiring January 2014 [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Number of Contracts

9,080

Open Futures Contracts, Long [Member] | United States [Member] | ICE Natural Gas Futures LD1 H February 2015 contracts, expiring January 2015 [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Number of Contracts

31,872

30,865

Prior to Reverse Split [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Net Asset Value Per Unit

5.51

Issued units

174,297,828

Following Reverse Split [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Net Asset Value Per Unit

22.04

Capital Units, Outstanding

43,574,457

Total Open Futures Contracts [Member] | Open Futures Contracts, Long [Member] | United States [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Number of Contracts

46,417

[3]

49,441

[4]

Creation Baskets [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Number of units per basket

100,000

Redemption Baskets [Member]

Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]

Number of units per basket

100,000

[1]

On February 21, 2012, there was a 4-for-1 reverse share split. The Financial Highlights have been adjusted for the periods shown to reflect the 4-for-1 reverse share split on a retroactive basis.

[2]

On February 21, 2012, there was a 4-for-1 reverse share split. The Statements of Changes in Partnersb Capital have been adjusted for the period shown to reflect the 4-for-1 reverse share split on a retroactive basis.

[3]

Collateral amounted to $226,156,153 on open future contracts.

[4]

Collateral amounted to $24,147,579 on open future contracts.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Additional Information) (Details)	12 Months Ended
	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Cash equivalents maturity period	6 months
Redemption Baskets [Member]
Significant Accounting Policies [Line Items]
Number of units per basket	100,000

Fees_Paid_by_the_Fund_and_Rela1

Fees Paid by the Fund and Related Party Transactions (Additional Information) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fees Paid and Related Party Transactions [Line Items]
USCF Management Fee	UNG is contractually obligated to pay USCF a fee, which is paid monthly, that is equal to 0.60% per annum of average daily total net assets of $1,000,000,000 or less and 0.50% per annum of average daily total net assets that are greater than $1,000,000,000.
Licensing fee incurred	$108,418	$143,884	$156,103
Estimated investor tax reporting cost	1,385,000	1,700,000	1,900,000
Estimated directors fees and expenses	191,887	199,863	172,837
USNG and the Related Public Funds [Member]
Fees Paid and Related Party Transactions [Line Items]
Estimated directors fees and expenses	567,863	555,465	540,586
UNITED STATES GAS FUND LP [Member]
Fees Paid and Related Party Transactions [Line Items]
Estimated directors fees and expenses	191,887	199,863	172,837
Licensing Agreements [Member]
Fees Paid and Related Party Transactions [Line Items]
Fee percentage	0.02%
Licensing Agreements [Member] | First $1,000,000,000 of combined net assets of the funds [Member]
Fees Paid and Related Party Transactions [Line Items]
Fee percentage	0.04%
Licensing Agreements [Member] | First $1,000,000,000 of combined net assets of the funds [Member] | Maximum [Member]
Fees Paid and Related Party Transactions [Line Items]
Basis Amount For Fee Percentage	1,000,000,000
Licensing Agreements [Member] | First $1,000,000,000 of combined net assets of the funds [Member] | Minimum [Member]
Fees Paid and Related Party Transactions [Line Items]
Basis Amount For Fee Percentage	1,000,000,000
Licensing Agreements [Member] | Combined net assets above $1,000,000,000 [Member]
Fees Paid and Related Party Transactions [Line Items]
Fee percentage	0.02%
United States Oil Fund LP [Member]
Fees Paid and Related Party Transactions [Line Items]
Ongoing Registration Fees and Other Offering Expenses	$238,716	$850	($18,588)

Contracts_and_Agreements_Broke

Contracts and Agreements (Brokerage Commission) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Floor Brokerage Exchange and Clearance Fees	$2,001,949	$2,400,039	$3,499,652
Rebalancing Investments Transaction [Member]
Floor Brokerage Exchange and Clearance Fees	1,623,581	2,036,257	2,954,424
Percentage Of Average Daily Net Assets	81.10%	84.84%	84.42%
Creation And Redemption Activity [Member]
Floor Brokerage Exchange and Clearance Fees	$378,368	$363,782	$545,228
Percentage Of Average Daily Net Assets	18.90%	15.16%	15.58%

Contracts_and_Agreements_Addit

Contracts and Agreements (Additional Information) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Annual Fee for custody, fund accounting and fund administration services	$20,000
Ratio of expense to Average Net Assets	0.28%	0.25%	0.33%
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 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 Futures Contracts and options on Futures Contracts	7
First $500 million of USNG's, USOF's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.06%
First $500 million of USNG's, USOF's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's 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
First $500 million of USNG's, USOF's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets [Member] | Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	1,000,000,000
USNG's, USOF's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's 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%
USNG's, USOF's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's 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
USNG's, USOF's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets exceed $1 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.04%
USNG's, USOF's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets exceed $1 billion [Member] | Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	1,000,000,000
Marketing Agreement [Member] | USNG's assets up to $3 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.06%
Marketing Agreement [Member] | USNG's assets up to $3 billion [Member] | Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	3,000,000,000
Marketing Agreement [Member] | USNG's assets in excess of $3 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.04%
Ratio of expense to Average Net Assets	10.00%
Marketing Agreement [Member] | USNG's assets in excess of $3 billion [Member] | Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	$3,000,000,000

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 collateral from counterparties	$0	$0
Securities collateral from counterparties	0	0
Derivative, Collateral, Obligation to Return Cash	0	0
Obligation to Return Securities Received as Collateral	0	19,477,185
Cash investments in money market funds	270,505,751	392,614,029
Deposits in domestic and foreign financial institutions	$545,522,548	$423,979,158

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		Apr. 18, 2007
Per Share Operating Performance:
Net asset value, beginning of year	$20.59	$18.87	$25.88	[1]	$25.88	[2]	$50
Total income (loss)	($5.70)	$1.93	($6.80)
Net expenses	($0.26)	($0.21)	($0.21)
Net increase (decrease) in net asset value	($5.96)	$1.72	($7.01)
Net asset value, end of year	$14.63	$20.59	$18.87		$25.88	[2]	$50
Total Return	-28.95%	9.11%	-27.09%
Ratios to Average Net Assets
Total income (loss)	-23.36%	17.44%	-26.42%
Expenses excluding management fees	0.54%	0.47%	0.49%
Management fees	0.60%	0.60%	0.59%
Net income (loss)	-24.51%	16.38%	-27.50%
[1]	On February 21, 2012, there was a 4-for-1 reverse share split. The Financial Highlights have been adjusted for the periods shown to reflect the 4-for-1 reverse share split on a retroactive basis.
[2]	On February 21, 2012, there was a 4-for-1 reverse share split. The Statements of Changes in Partnersb Capital have been adjusted for the period shown to reflect the 4-for-1 reverse share split on a retroactive basis.

Quarterly_Financial_Data_Unaud2

Quarterly Financial Data (Unaudited) (Summarized Quarterly Financial Information) (Detail) (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
Quarterly Financial Information [Line Items]
Total income (loss)	($275,233,339)	($64,717,705)	$15,991,068	$155,083,163	$131,829,654	($13,383,047)	($117,977,008)	$166,838,065	($168,876,813)	$167,307,664	($274,882,968)
Total expenses	1,892,746	2,049,423	2,069,407	2,262,092	2,506,395	2,510,685	2,473,605	2,717,110	8,273,668	10,207,795	11,283,153
Net income (loss)	($277,126,085)	($66,767,128)	$13,921,661	$152,821,071	$129,323,259	($15,893,732)	($120,450,613)	$164,120,955	($177,150,481)	$157,099,869	($286,166,121)
Net income (loss) per share	($7.47)	($2.48)	$0.23	$3.76	$2.29	($0.59)	($3.04)	$3.06	($5.96)	$1.72	($7.01)

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
Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	$520,470,896	$742,544,890
Exchange-Traded Futures Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	-167,811,783	-14,033,910
Exchange-Traded Cleared Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		0
Open Over-the-Counter Total Return Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		-6,654,820
Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	520,470,896	742,544,890
Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	-167,811,783	-14,033,910
Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Cleared Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		0
Fair Value, Inputs, Level 1 [Member] | Open Over-the-Counter Total Return Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		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 2 [Member] | Exchange-Traded Futures Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
Fair Value, Inputs, Level 2 [Member] | Exchange-Traded Cleared Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		0
Fair Value, Inputs, Level 2 [Member] | Open Over-the-Counter Total Return Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		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, Inputs, Level 3 [Member] | Exchange-Traded Futures Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value	0	0
Fair Value, Inputs, Level 3 [Member] | Exchange-Traded Cleared Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		0
Fair Value, Inputs, Level 3 [Member] | Open Over-the-Counter Total Return Swap Contracts [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Securities, fair value		($6,654,820)

Fair_Value_Of_Financial_Instru3

Fair Value Of Financial Instruments (Reconciliation of Assets in which Significant Observable Inputs (Level III) were used in Determining Fair Value) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Total Return Swap Contracts
Realized gain (loss)	$25,690,444		$13,643,971		($75,525,786)
Change in unrealized gain (loss)	6,654,820		-3,183,881		9,334,753
Total Return Swap Contracts [Member]
Total Return Swap Contracts
Beginning balance	-6,654,820		-3,470,939
Realized gain (loss)	0	[1]	0	[2]
Change in unrealized gain (loss)	6,654,820		-3,183,881
Ending balance	$0		($6,654,820)
[1]	The realized gain (loss) incurred during the fiscal year ended December 31, 2014 for total return swaps was $25,690,444
[2]	The realized loss incurred during the fiscal year ended December 31, 2013 for total return swaps was $13,643,971.

Fair_Value_Of_Financial_Instru4

Fair Value Of Financial Instruments (Reconciliation of Assets in which Significant Observable Inputs (Level III) were used in Determining Fair Value) (Parenthetical) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Total Return Swap Contracts
Realized gain (loss)	$25,690,444	$13,643,971	($75,525,786)
Total Return Swap [Member]
Total Return Swap Contracts
Realized gain (loss)	$25,690,444	$13,643,971

Fair_Value_Of_Financial_Instru5

Fair Value Of Financial Instruments (Fair Value of Derivative Instruments) (Details) (Commodity Contracts [Member], Assets [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
Futures - Commodity Contracts [Member]
Fair Value of Financial Instruments [Line Items]
Derivatives not Accounted for as Hedging Instruments	($167,811,783)	($14,033,910)
Swaps - Commodity Contracts [Member]
Fair Value of Financial Instruments [Line Items]
Derivatives not Accounted for as Hedging Instruments	$0	($6,654,820)

Fair_Value_Of_Financial_Instru6

Fair Value Of Financial Instruments (Effect of Derivative Instruments on Condensed Statements of Operations) (Details) (Commodity Contracts [Member], USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Futures - Commodity Contracts [Member] | Realized gain on closed futures positions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain on Derivatives or (Loss) Recognized in Income	($47,954,734)	$155,734,315	($243,672,550)
Futures - Commodity Contracts [Member] | Change in unrealized gain or (loss) on open futures positions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income	-153,777,873	562,933	34,395,462
Swaps - Commodity Contracts [Member] | Realized gain or (loss) on closed swap contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain on Derivatives or (Loss) Recognized in Income	25,690,444	13,643,971	-75,525,786
Swaps - Commodity Contracts [Member] | Change in unrealized gain on open swap contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income	$6,654,820	($3,183,881)	$9,334,753