United States Natural Gas Fund (UNG) 10-Q 12 Nov 13 2013 Q3 Quarterly report Financial data

Document_And_Entity_Informatio

Document And Entity Information	9 Months Ended
	Sep. 30, 2013
Document Information [Line Items]	'
Document Type	'10-Q
Amendment Flag	'false
Document Period End Date	30-Sep-13
Document Fiscal Year Focus	'2013
Document Fiscal Period Focus	'Q3
Trading Symbol	'UNG
Entity Common Stock, Shares Outstanding	0
Entity Registrant Name	'United States Natural Gas Fund, LP
Entity Central Index Key	'0001376227
Current Fiscal Year End Date	'--12-31
Entity Filer Category	'Large Accelerated Filer

Condensed_Statements_of_Financ

Condensed Statements of Financial Condition (USD $)	Sep. 30, 2013	Dec. 31, 2012
Assets	'	'
Cash and cash equivalents (Notes 2 and 5)	$847,246,412	$1,100,510,722
Equity in UBS Securities LLC trading accounts:	'	'
Cash and cash equivalents	130,182,040	144,803,499
Unrealized loss on open commodity futures contracts	-47,006,220	-14,596,843
Unrealized gain (loss) on open swap contracts	394,058	-3,470,939
Receivable for units sold	11,004,516	19,007,766
Dividend receivable	9,304	16,356
Other assets	37,013	11,953
Total assets	941,867,123	1,246,282,514
Liabilities and Partners' Capital	'	'
Payable for units redeemed	0	57,644,550
Professional fees payable	1,100,993	1,602,883
General Partner management fees payable (Note 3)	462,739	585,420
Brokerage commissions payable	81,750	122,250
Interest payable	153	153
Other liabilities	42,631	54,602
Total liabilities	1,688,266	60,009,858
Commitments and Contingencies (Notes 3, 4 and 5)	'	'
Partners' Capital	'	'
General Partner	0	0
Limited Partners	940,178,857	1,186,272,656
Total Partners' Capital	940,178,857	1,186,272,656
Total liabilities and partners' capital	$941,867,123	$1,246,282,514
Limited Partners' units outstanding	51,366,476	62,866,476
Net asset value per unit	$18.30	$18.87
Market value per unit	$18.28	$18.90

Condensed_Schedule_of_Investme

Condensed Schedule of Investments (USD $)

9 Months Ended

9 Months Ended

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Sep. 30, 2013

Open Futures Contracts, Long [Member]

Open Futures Contracts, Long [Member]

Open Futures Contracts, Long [Member]

Open Over-the-Counter Total Return Swap Contracts [Member]

Total Open Futures Contracts [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

Cash Equivalents [Member]

United States [Member]

United States [Member]

United States [Member]

Swap Agreement to Receive Return on the Custom Natural Gas Index (UNG) - Excess Return [Member]

Open Futures Contracts, Long [Member]

United States [Member]

United States [Member]

United States [Member]

United States [Member]

United States [Member]

United States [Member]

United States [Member]

United States [Member]

ICE Natural Gas Futures LD1 H November 2013 contracts, expiring october 2013 [Member]

NYMEX Natural Gas Futures NG November 2013 contracts, expiring october 2013 [Member]

NYMEX Natural Gas Futures NN November 2013 contracts, expiring october 2013 [Member]

United States [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

Money Market Funds [Member]

Money Market Funds [Member]

Money Market Funds [Member]

Money Market Funds [Member]

Money Market Funds [Member]

Contract

Contract

Contract

Contract

U.S. Treasury Bills, 0.07%, 10/31/2013 [Member]

U.S. Treasury Bills,0.06%, 11/21/2013 [Member]

Fidelity Institutional Government Portfolio - Class I [Member]

Goldman Sachs Financial Square Funds - Government Fund - Class SL

Morgan Stanley Institutional Liquidity Fund - Government Portfolio [Member]

Wells Fargo Advantage Government Money Market Fund - Class I [Member]

Contracts Notional Amount

'

'

'

$100,892,244

[1]

'

'

'

'

'

'

'

'

'

'

Number of contracts

29,993

13,580

9,952

'

53,525

[2]

'

'

'

'

'

'

'

'

'

Principal Amount

'

'

'

'

'

'

'

100,000,000

[3]

65,000,000

'

101,608,278

150,508,087

200,495,952

100,001,712

Unrealized loss on open commodity futures contracts

-16,180,090

-25,455,160

-5,370,970

'

-47,006,220

'

'

'

'

'

'

'

'

'

Market Value

'

'

'

394,058

'

717,602,424

164,988,395

99,993,920

[3]

64,994,475

552,614,029

101,608,278

150,508,087

200,495,952

100,001,712

Unrealized Gain

'

'

'

394,058

'

'

'

'

'

'

'

'

'

'

% of Partners' Capital

-1.72%

-2.71%

-0.57%

'

-5.00%

[2]

76.33%

17.55%

10.64%

[3]

6.91%

58.78%

10.81%

16.01%

21.32%

10.64%

Termination Dates

'October 2013

'October 2013

'October 2013

'10/23/2013

'

'

'

'10/31/2013

[3]

'11/21/2013

'

'

'

'

'

Collateral Pledged

'

'

'

$15,239,140

[4]

'

'

'

'

'

'

'

'

'

'

[1]

The aggregate notional amount of USNG’s over-the-counter swap transactions represented 10.71% of USNG’s total assets as of September 30, 2013.

[2]

Collateral amounted to $130,185,922 on open futures contracts.

[3]

Security or partial security segregated as collateral for open over-the-counter total return swap contracts.

[4]

Financial instruments.

Condensed_Schedule_of_Investme1

Condensed Schedule of Investments (Parenthetical) (USD $)	9 Months Ended
	Sep. 30, 2013
Swap transaction as a percentage of total asset	10.71%
Collateral Amount On Open Futures Contracts	130,185,922
United States [Member] | ICE Natural Gas Futures LD1 H August 2013 contracts, expiring August 2013 [Member] | Open Futures Contracts, Long [Member]	'
Expiration date	'October 2013
United States [Member] | NYMEX Natural Gas Futures NG November 2013 contracts, expiring october 2013 [Member] | Open Futures Contracts, Long [Member]	'
Expiration date	'October 2013
United States [Member] | NYMEX Natural Gas Futures NN November 2013 contracts, expiring october 2013 [Member] | Open Futures Contracts, Long [Member]	'
Expiration date	'October 2013
United States [Member] | U.S. Treasury Bills, 0.07%, 10/31/2013 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]	'
Interest rate	0.07%	[1]
Expiration date	'10/31/2013	[1]
United States [Member] | U.S. Treasury Bills,0.06%, 11/21/2013 [Member] | US Treasury Securities [Member] | Cash Equivalents [Member]	'
Interest rate	0.06%
Expiration date	'11/21/2013
[1]	Security or partial security segregated as collateral for open over-the-counter total return swap contracts.

Condensed_Statements_of_Operat

Condensed Statements of Operations (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Gain (loss) on trading of commodity contracts:	'	'	'	'
Realized gain (loss) on closed futures contracts	($7,662,805)	$120,434,518	$69,898,707	($200,481,655)
Realized gain (loss) on closed swap contracts	-14,494,336	21,863,449	-6,290,828	-64,420,592
Change in unrealized gain (loss) on open futures contracts	-2,591,930	-34,822,414	-32,409,377	109,485,403
Change in unrealized gain (loss) on open swap contracts	11,245,517	-1,242,090	3,864,997	22,100,866
Dividend income	28,790	29,534	100,407	82,332
Interest income	40,717	85,497	141,104	150,367
Other income	51,000	60,000	173,000	166,000
Total income (loss)	-13,383,047	106,408,494	35,478,010	-132,917,279
Expenses	'	'	'	'
General Partner management fees (Note 3)	1,392,568	1,671,929	4,317,497	4,387,127
Brokerage commissions	615,823	848,929	1,814,781	2,799,540
Professional fees	415,870	276,910	1,313,124	891,829
Other expenses	86,424	86,878	255,998	220,730
Total expenses	2,510,685	2,884,646	7,701,400	8,299,226
Net income (loss)	($15,893,732)	$103,523,848	$27,776,610	($141,216,505)
Net income (loss) per limited partnership unit	($0.59)	$2.09	($0.57)	($4.52)
Net income (loss) per weighted average limited partnership unit	($0.32)	$1.79	$0.57	($2.73)
Weighted average limited partnership units outstanding	49,127,346	57,783,867	48,795,780	51,759,859

Condensed_Statements_of_Change

Condensed Statements of Changes in Partners' Capital (USD $)	Total	General Partner [Member]	Limited Partners [Member]
Balances, at December 31, 2012 at Dec. 31, 2012	$1,186,272,656	$0	$1,186,272,656
Net asset value, beginning of period at Dec. 31, 2012	$18.87	'	'
Addition of 86,600,000 partnership units	1,700,911,332	0	1,700,911,332
Redemption of 98,100,000 partnership units	-1,974,781,741	0	-1,974,781,741
Net income	27,776,610	0	27,776,610
Balances, at September 30, 2013 at Sep. 30, 2013	$940,178,857	$0	$940,178,857
Net asset value, end of period at Sep. 30, 2013	$18.30	'	'

Condensed_Statements_of_Change1

Condensed Statements of Changes in Partners' Capital (Parenthetical)	9 Months Ended
	Sep. 30, 2013
Addition of partnership units	86,600,000
Redemption of partnership units	98,100,000

Condensed_Statements_of_Cash_F

Condensed Statements of Cash Flows (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash Flows from Operating Activities:	'	'
Net Income (Loss)	$27,776,610	($141,216,505)
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	14,621,459	-44,148,580
Unrealized (gain) loss on open futures contracts	32,409,377	-109,485,403
Unrealized gain on open swap contracts	-3,864,997	-22,100,866
(Increase) decrease in dividend receivable	7,052	-1,553
Increase in interest receivable	0	-373
Increase in other assets	-25,060	-8,602
Decrease in investment payable	0	-772
Decrease in professional fees payable	-501,890	-884,979
Decrease in General Partner management fees payable	-122,681	-57,467
Decrease in brokerage commissions payable	-40,500	-30,000
Decrease in other liabilities	-11,971	-32,500
Net cash provided by (used in) operating activities	70,247,399	-317,967,600
Cash Flows from Financing Activities:	'	'
Addition of partnership units	1,708,914,582	1,949,325,153
Redemption of partnership units	-2,032,426,291	-1,723,420,515
Net cash provided by (used in) financing activities	-323,511,709	225,904,638
Net Decrease in Cash and Cash Equivalents	-253,264,310	-92,062,962
Cash and Cash Equivalents, beginning of period	1,100,510,722	938,678,961
Cash and Cash Equivalents, end of period	$847,246,412	$846,615,999

Organization_and_Business

Organization and Business	9 Months Ended
	Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Organization and Business	'
	NOTE 1 — ORGANIZATION AND BUSINESS
	The United States Natural Gas Fund, LP (“USNG”) was organized as a limited partnership under the laws of the state of Delaware on September 11, 2006. USNG is a commodity pool that issues limited partnership units (“units”) that may be purchased and sold on the NYSE Arca, Inc. (the “NYSE Arca”). Prior to November 25, 2008, USNG’s units traded on the American Stock Exchange (the “AMEX”). USNG 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 USNG is for the daily changes in percentage terms of its units’ per unit 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 as 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 USNG’s expenses. It is not the intent of USNG to be operated in a fashion such that the per unit 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 USNG to be operated in a fashion such that its per unit 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 USNG, believes that it is not practical to manage the portfolio to achieve such an investment goal when investing in Natural Gas Futures Contracts (as defined below) and Other Natural Gas-Related Investments (as defined below). The net assets of USNG consist primarily of investments in futures contracts for natural gas that are traded on the NYMEX, ICE Futures Exchange (“ICE Futures”) or other U.S. and foreign exchanges (collectively, “Natural Gas Futures Contracts”) and, to a lesser extent, in order to comply with regulatory requirements or in view of market conditions, other natural gas-related investments such as cash-settled options on Natural Gas Futures Contracts, forward contracts for natural gas, cleared swap contracts, and non-exchange traded (“over-the-counter”) transactions that are based on the price of natural gas, crude oil and other petroleum-based fuels, as well as futures contracts for crude oil, heating oil, gasoline and other petroleum-based fuels and indices based on the foregoing (collectively, “Other Natural Gas-Related Investments”). Market conditions that USCF currently anticipates could cause USNG to invest in Other Natural Gas-Related Investments including those allowing USNG to obtain greater liquidity or to execute transactions with more favorable pricing. For convenience and unless otherwise specified, Natural Gas Futures Contracts and Other Natural Gas-Related Investments collectively are referred to as “Natural Gas Interests” in this quarterly report on Form 10-Q. USCF is authorized by USNG in its sole judgment to employ, establish the terms of employment for and terminate commodity trading advisors of futures commission merchants. As of September 30, 2013, USNG held 13,580 NG Futures November 2013 Contracts and 9,952 NN Financially Settled Futures November 2013 Contracts traded on the NYMEX, 29,993 LD1 H Futures November 2013 Contracts traded on the ICE Futures US, and over-the-counter swap transactions with two counterparties, JPMorgan Chase Bank, NA and Deutsche Bank AG. The over-the-counter swap transaction with Deutsche Bank AG was terminated effective September 30, 2013.
	USNG commenced investment operations on April 18, 2007 and has a fiscal year ending on December 31. USCF is responsible for the management of USNG. 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 (“USOF”), the United States 12 Month Oil Fund, LP (“US12OF”), the United States Gasoline Fund, LP (“UGA”) and the United States Diesel-Heating Oil Fund, LP (formerly, the United States Heating Oil Fund, LP) (“USDHO”), which listed their limited partnership units 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 USOF’s, US12OF’s, UGA’s and USDHO’s units commenced trading on the NYSE Arca on November 25, 2008. USCF is also the general partner of the United States Short Oil Fund, LP (“USSO”), the United States 12 Month Natural Gas Fund, LP (“US12NG”) and the United States Brent Oil Fund, LP (“USBO”), which listed their limited partnership units 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. USCI, CPER, USAG and USMI listed their units on the NYSE Arca under the ticker symbol “USCI” on August 10, 2010, “CPER” on November 15, 2011, “USAG” on April 13, 2012 and “USMI” on June 19, 2012, respectively. All funds listed previously are referred to collectively herein as the “Related Public Funds.” USCF has also filed registration statements to register units of the United States Sugar Fund (“USSF”), the United States Natural Gas Double Inverse Fund (“UNGD”), the United States Gasoil Fund (“USGO”) and the United States Asian Commodities Basket Fund (“UAC”), each a series of the United States Commodity Funds Trust I, and the US Golden Currency Fund (“HARD”), a series of the United States Currency Funds Trust. USSF, UNGD, USGO and HARD are currently not available to the public, as such funds are still in the process of review by various regulatory agencies which have regulatory authority over USCF and such funds. UAC has been declared effective by the regulatory agencies which have regulatory authority over USCF and UAC, but at the time of the filing of this quarterly report on Form 10-Q, UAC has not been made available to the public.
	USNG issues units to certain authorized purchasers (“Authorized Purchasers”) by offering baskets consisting of 100,000 units (“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 unit 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 Purchasers pay USNG 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 units. Units may be purchased or sold on a nationally recognized securities exchange in smaller increments than a Creation Basket or Redemption Basket. Units purchased or sold on a nationally recognized securities exchange are not purchased or sold at the per unit NAV of USNG but rather at market prices quoted on such exchange.
	In April 2007, USNG initially registered 30,000,000 units on Form S-1 with the U.S. Securities and Exchange Commission (the “SEC”). On April 18, 2007, USNG listed its units on the AMEX under the ticker symbol “UNG”. On that day, USNG established its initial per unit NAV by setting the price at $50.00 and issued 200,000 units in exchange for $10,001,000. USNG also commenced investment operations on April 18, 2007, by purchasing Natural Gas Futures Contracts traded on the NYMEX based on natural gas. As of September 30, 2013, USNG had registered a total of 430,100,000 units.
	On February 21, 2012, after the close of trading on the NYSE Arca, USNG effected a 4-for-1 reverse unit split and post-split units of USNG began trading on February 22, 2012. As a result of the reverse unit split, every four pre-split units of USNG were automatically exchanged for one post-split unit. Immediately prior to the reverse split, there were 174,297,828 units of USNG issued and outstanding, representing a per unit NAV of $5.51. Immediately after the reverse unit split, the number of issued and outstanding units of USNG decreased to 43,574,457, not accounting for fractional units, and the per unit NAV increased to $22.04. In connection with the reverse unit split, the CUSIP number of USNG’s units changed to 912318201. USNG’s ticker symbol, “UNG,” remains the same.
	The accompanying unaudited condensed financial statements have been prepared in accordance with Rule 10-01 of Regulation S-X promulgated by the SEC and, therefore, do not include all information and footnote disclosure required under generally accepted accounting principles (“GAAP”) in the United States of America. The financial information included herein is unaudited; however, such financial information reflects all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of USCF, necessary for the fair presentation of the condensed financial statements for the interim period.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2013
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 condensed 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 condensed financial statements. Changes in the unrealized gains or losses between periods are reflected in the condensed statements of operations. USNG earns interest on its assets denominated in U.S. dollars on deposit with the futures commission merchant at the overnight Federal Funds Rate less 32 basis points. In addition, USNG earns income on funds held at the custodian or futures commission merchant at prevailing market rates earned on such investments.
	Investments in over-the-counter total return 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 commodity future, security or index underlying the transaction exceeds or falls short of the offsetting periodic payment obligation, USNG 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 condensed 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 USNG for over-the-counter swap contracts are reflected on the condensed 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
	USNG 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 GAAP, USNG 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. USNG files an income tax return in the U.S. federal jurisdiction, and may file income tax returns in various U.S. states. USNG is not subject to income tax return examinations by major taxing authorities for years before 2009. 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 USNG recording a tax liability that reduces net assets. However, USNG’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. USNG 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 period ended September 30, 2013.
	Creations and Redemptions
	Authorized Purchasers may purchase Creation Baskets or redeem Redemption Baskets only in blocks of 100,000 units at a price equal to the NAV of the units calculated shortly after the close of the core trading session on the NYSE Arca on the day the order is placed.
	USNG receives or pays the proceeds from units sold or redeemed within three business days after the trade date of the purchase or redemption. The amounts due from Authorized Purchasers are reflected in USNG’s condensed statements of financial condition as receivable for units sold, and amounts payable to Authorized Purchasers upon redemption are reflected as payable for units redeemed.
	Partnership Capital and Allocation of Partnership Income and Losses
	Profit or loss shall be allocated among the partners of USNG in proportion to the number of units 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
	USNG’s per unit 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 units outstanding. USNG 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 Unit
	Net income (loss) per unit is the difference between the per unit NAV at the beginning of each period and at the end of each period. The weighted average number of units outstanding was computed for purposes of disclosing net income (loss) per weighted average unit. The weighted average units are equal to the number of units outstanding at the end of the period, adjusted proportionately for units added and redeemed based on the amount of time the units were outstanding during such period. There were no units held by USCF at September 30, 2013.
	Offering Costs
	Offering costs incurred in connection with the registration of additional units after the initial registration of units are borne by USNG. 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 condensed financial statements were reclassified to conform to the current presentation.
	Use of Estimates
	The preparation of condensed 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 condensed 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, USNG effected a 4-for-1 reverse unit split and post-split units of USNG began trading on February 22, 2012. The unaudited condensed financial information reported in this quarterly report on Form 10-Q gives effect to the reverse split and the post-split of units as if they had been completed on January 1, 2012.
	The unaudited condensed financial information and pro forma financial information, as well as the historical financial information as of and for the year ended December 31, 2012, was derived from USNG’s historical financial statements and has been audited by Spicer Jeffries LLP. The financial information as of and for the nine months ended September 30, 2013 is unaudited. The condensed financial statements in this quarterly report on Form 10-Q 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	9 Months Ended
	Sep. 30, 2013
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 USNG in accordance with the objectives and policies of USNG. In addition, USCF has arranged for one or more third parties to provide administrative, custody, accounting, transfer agency and other necessary services to USNG. For these services, USNG 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
	USNG pays all costs and expenses associated with the ongoing registration of its units subsequent to the initial offering. These costs include registration or other fees paid to regulatory agencies in connection with the offer and sale of units, and all legal, accounting, printing and other expenses associated with such offer and sale. For the nine months ended September 30, 2013 and 2012, USNG did not incur registration fees and other offering expenses.
	Directors’ Fees and Expenses
	USNG is responsible for paying its portion of the directors’ and officers’ liability insurance for USNG and the Related Public Funds and the fees and expenses of the independent directors who also serve as audit committee members of USNG 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. USNG 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 ending December 31, 2013 are estimated to be a total of $560,625 for USNG and the Related Public Funds.
	Licensing Fees
	As discussed in Note 4 below, USNG 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, USNG and the Related Public Funds, other than USBO, 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, USNG and the Related Public Funds, other than USBO, USCI, CPER, USAG and USMI, pay a licensing fee that is equal to 0.015% on all net assets. During the nine months ended September 30, 2013 and 2012, USNG incurred $108,358 and $110,617, respectively, under this arrangement.
	Investor Tax Reporting Cost
	The fees and expenses associated with USNG’s audit expenses and tax accounting and reporting requirements are paid by USNG. These costs are estimated to be $1,600,000 for the year ending December 31, 2013.
	Other Expenses and Fees
	In addition to the fees described above, USNG pays all brokerage fees, transaction costs for over-the-counter swaps and other expenses in connection with the operation of USNG, including the costs incurred with the preparation and execution of the reverse split, but excluding costs and expenses paid by USCF as outlined in Note 4 below

Contracts_and_Agreements

Contracts and Agreements	9 Months Ended
	Sep. 30, 2013
Contractors [Abstract]	'
Contracts and Agreements	'
	NOTE 4 — CONTRACTS AND AGREEMENTS
	USNG 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 USNG as outlined in the agreement. The fee of the Marketing Agent, which is borne by USCF, is equal to 0.06% on USNG’s assets up to $3 billion and 0.04% on USNG’s assets in excess of $3 billion.
	The above fee does not include the following expenses, which are also borne by USCF: the cost of placing advertisements in various periodicals; website construction and development; or the printing and production of various marketing materials.
	USNG 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 USNG. USCF pays the fees of the custodian, which are determined by the parties from time to time. In addition, USNG 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 USNG. 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 USNG 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 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, (b) 0.0465% for 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, and (c) 0.035% once 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. 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, USNG entered into a brokerage agreement with RBC Capital Markets, LLC (“RBC Capital” or “RBC”) to serve as USNG’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 USNG in connection with the purchase and sale of Natural Gas Futures Contracts and Other Natural Gas-Related Investments that may be purchased and sold by or through RBC Capital and/or UBS Securities for USNG’s account. In accordance with each agreement, RBC Capital and UBS Securities charge USNG commissions of approximately $7 to $15 per round-turn trade, including applicable exchange and NFA fees for Natural Gas Futures Contracts and options on Natural Gas Futures Contracts. Such fees include those incurred when purchasing Natural Gas Futures Contracts and options on Natural Gas Futures Contracts when USNG issues units as a result of a Creation Basket, as well as fees incurred when selling Natural Gas Futures Contracts and options on Natural Gas Futures Contracts when USNG redeems units as a result of a Redemption Basket. Such fees are also incurred when Natural Gas Futures Contracts and options on Natural Gas Futures Contracts are purchased or redeemed for the purpose of rebalancing the portfolio. USNG also incurs commissions to brokers for the purchase and sales of Natural Gas Futures Contracts, Other Natural Gas-Related Investments or short-term obligations of the United States of two years or less (“Treasuries”). During the nine months ended September 30, 2013, total commissions accrued to brokers amounted to $1,814,781. Of this amount, approximately $1,540,235 was a result of rebalancing costs and approximately $274,546 was the result of trades necessitated by creation and redemption activity. By comparison, during the nine months ended September 30, 2012, total commissions accrued to brokers amounted to $2,799,540. Of this amount, approximately $2,370,831 was the result of rebalancing costs and approximately $428,709 was the result of trades necessitated by creation and redemption activity. The decrease in the total commissions accrued to brokers for the nine months ended September 30, 2013, as compared to the nine months ended September 30, 2012, was a function 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 nine months ended September 30, 2013. As an annualized percentage of average daily total net assets, the figure for the nine months ended September 30, 2013 represents approximately 0.25% of average daily total net assets. By comparison, the figure for the nine months ended September 30, 2012 represented approximately 0.38% 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.
	USNG and the NYMEX entered into a licensing agreement on April 10, 2006, as amended on October 20, 2011, whereby USNG was granted a non-exclusive license to use certain of the NYMEX’s settlement prices and service marks. Under the licensing agreement, USNG and the Related Public Funds, other than USBO, USCI, CPER, USAG and USMI, pay the NYMEX an asset-based fee for the license, the terms of which are described in Note 3. USNG expressly disclaims any association with the NYMEX or endorsement of USNG 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	9 Months Ended
	Sep. 30, 2013
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
	USNG engages in the trading of futures contracts, options on futures contracts, cleared swaps and over-the-counter swaps (collectively, “derivatives”). USNG 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.
	USNG 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 over-the-counter 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 futures commission merchant. Additional deposits may be necessary for any loss on contract value. The Commodity Exchange Act requires a futures commission merchant to segregate all customer transactions and assets from the futures commission merchant’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 USNG 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.
	All of USNG’s investment contracts were exchange-traded futures contracts or fully-collateralized over-the-counter swaps through September 30, 2013. 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. At September 30, 2013, USNG maintained over-the-counter swap transactions with two counterparties, JPMorgan Chase Bank, NA and Deutsche Bank AG. The over-the-counter swap transaction with Deutsche Bank AG expired effective September 30, 2013. Over-the-counter swap transactions subject USNG 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. USNG 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, USNG bears the risk of financial failure by the clearing broker.
	At September 30, 2013, USNG’s counterparties posted $0 in cash and $1,214,685 in securities as collateral with USNG’s custodian, as compared with $5,000,533 in cash and $1,191,737 in securities at September 30, 2012. Under these over-the-counter swap agreements, USNG posted collateral with respect to its obligations of $0 in cash and $1,214,685 in securities, such as Treasuries, at September 30, 2013, as compared with $16,144,536 in cash and $15,298,350 in securities at September 30, 2012.
	USNG’s cash and other property, such as Treasuries, deposited with a futures commission merchant are considered commingled with all other customer funds, subject to the futures commission merchant’s segregation requirements. In the event of a futures commission merchant’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 futures commission merchant could result in the complete loss of USNG’s assets posted with that futures commission merchant; however, the majority of USNG’s assets are held in Treasuries, cash and/or cash equivalents with USNG’s custodian and would not be impacted by the insolvency of a futures commission merchant. The failure or insolvency of USNG’s custodian, however, could result in a substantial loss of USNG’s assets.
	USCF invests a portion of USNG’s cash in money market funds that seek to maintain a stable per unit NAV. USNG is exposed to any risk of loss associated with an investment in such money market funds. As of September 30, 2013 and December 31, 2012, USNG held investments in money market funds in the amounts of $552,614,029 and $552,614,029, respectively. USNG 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 September 30, 2013 and December 31, 2012, USNG held cash deposits and investments in Treasuries in the amounts of $424,814,423 and $692,700,192, respectively, with the custodian and futures commission merchant. Some or all of these amounts may be subject to loss should USNG’s custodian and/or futures commission merchant cease operations.
	For derivatives, risks arise from changes in the market value of the contracts. Theoretically, USNG 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, USNG 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.
	USNG’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, USNG 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 USNG are reported in its condensed 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	9 Months Ended
	Sep. 30, 2013
Financial Highlights [Abstract]	'
Financial Highlights	'
	NOTE 6 — FINANCIAL HIGHLIGHTS
	The following table presents per unit performance data and other supplemental financial data for the nine months ended September 30, 2013 and 2012 for the unitholders. This information has been derived from information presented in the condensed financial statements.
		For the nine months ended			For the nine months ended
		September 30, 2013			September 30, 2012
		(Unaudited)			(Unaudited)
	Per Unit Operating Performance:
	Net asset value, beginning of period	$	18.87		$	25.88	*
	Total loss		-0.41			-4.36
	Total expenses		-0.16			-0.16
	Net decrease in net asset value		-0.57			-4.52
	Net asset value, end of period	$	18.3		$	21.36
	Total Return		-3.02	%		-17.47	%
	Ratios to Average Net Assets
	Total income (loss)		3.67	%		-13.49	%
	Expenses excluding management fees**		0.47	%		0.53	%
	Management fees**		0.6	%		0.59	%
	Net income (loss)		2.88	%		-14.34	%
	*      On February 21, 2012, there was a 4-for-1 reverse unit split. The Financial Highlights (Unaudited) have been adjusted for the period shown to reflect the 4-for-1 reverse unit split on a retroactive basis.
	**   Annualized.
	Total returns are calculated based on the change in value during the period. An individual unitholder’s total return and ratio may vary from the above total returns and ratios based on the timing of contributions to and withdrawals from USNG.

Fair_Value_Of_Financial_Instru

Fair Value Of Financial Instruments

9 Months Ended

Sep. 30, 2013

Fair Value Disclosures [Abstract]

'

Fair Value Of Financial Instruments

'

NOTE 7 — FAIR VALUE OF FINANCIAL INSTRUMENTS

USNG 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 USNG (observable inputs) and (2) USNG’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 USNG’s securities at September 30, 2013 using the fair value hierarchy:

At September 30, 2013

Total

Level I

Level II

Level III

Short-Term Investments

$

717,602,424

$

717,602,424

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

-47,006,220

-47,006,220

—

—

Over-the-Counter Total Return Swap Contracts

394,058

—

—

394,058

During the nine months ended September 30, 2013, there were no transfers between Level I and Level II.

Following is a reconciliation of assets in which significant unobservable inputs (Level III) were used in determining fair value as of September 30, 2013:

Total Return Swap Contracts

Beginning balance as of 12/31/12

$

-3,470,939

Realized gain (loss)*

—

Change in unrealized gain (loss)

3,864,997

Ending balance as of 09/30/13

$

394,058

*

The realized gain (loss) incurred during the nine months ended September 30, 2013 for total return swaps was $(6,290,828).

The following table summarizes the valuation of USNG’s securities at December 31, 2012 using the fair value hierarchy:

At December 31, 2012

Total

Level I

Level II

Level III

Short-Term Investments

$

882,586,367

$

882,586,367

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

-14,596,843

-14,596,843

—

—

Over-the-Counter Total Return Swap Contracts

-3,470,939

—

—

-3,470,939

During the year ended December 31, 2012, there were no transfers between Level I and Level II.

Following is a reconciliation of assets in which significant unobservable inputs (Level III) were used in determining fair value as of December 31, 2012:

Total Return Swap Contracts

Beginning balance as of 12/31/11

$

-12,805,692

Realized gain (loss)*

—

Change in unrealized gain (loss)

9,334,753

Ending balance as of 12/31/12

$

-3,470,939

*

The realized gain (loss) incurred during the fiscal year ended December 31, 2012 for total return swaps was $(75,525,786).

Effective January 1, 2009, USNG 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

Condensed

Fair Value

Fair Value

Accounted for

Statements of Financial

At September 30, 2013

At December 31, 2012

as Hedging

Condition Location

Instruments

Futures - Commodity Contracts

Assets

$

-47,006,220

$

-14,596,843

Swaps - Commodity Contracts

Assets

394,058

-3,470,939

The Effect of Derivative Instruments on the Condensed Statements of Operations

For the nine months ended

For the nine months ended

September 30, 2013

September 30, 2012

Derivatives not

Location of

Realized

Change in

Realized

Change in

Accounted for

Gain or (Loss)

Gain or (Loss)

Unrealized

Gain or (Loss)

Unrealized

as Hedging

on Derivatives

on Derivatives

Gain or (Loss)

on Derivatives

Gain or (Loss)

Instruments

Recognized in

Recognized in

on Derivatives

Recognized in

on Derivatives

Income

Income

Recognized in

Income

Recognized in

Income

Income

Futures -

Realized gain (loss) on closed futures positions

$

69,898,707

$

-200,481,655

Commodity Contracts

Change in unrealized gain (loss) on open futures positions

$

-32,409,377

$

109,485,403

Swaps -

Realized gain (loss) on closed swap contracts

$

-6,290,828

$

-64,420,592

Commodity Contracts

Change in unrealized gain (loss) on open swap contracts

$

3,864,997

$

22,100,866

Subsequent_Events

Subsequent Events	9 Months Ended
	Sep. 30, 2013
Subsequent Events [Abstract]	'
Subsequent Events	'
	NOTE 8 — SUBSEQUENT EVENTS
	USNG has performed an evaluation of subsequent events through the date the condensed financial statements were issued. The subsequent events, which did not necessitate disclosures and/or adjustments to the financial statements, were as follows:
	On October 8, 2013, USCF entered into a Futures and Cleared Derivatives Transactions Customer Account Agreement with RBC Capital to serve as USNG’s FCM, effective October 10, 2013.  Prior to October 10, 2013, UBS Securities was USNG’s FCM. This agreement requires RBC Capital to provide services to USNG, as of October 10, 2013, in connection with the purchase and sale of Natural Gas Futures Contracts and Other Natural Gas-Related Investments that may be purchased or sold by or through RBC Capital for USNG’s account. For the period October 10, 2013 and after, USNG pays RBC Capital commissions for executing and clearing trades on behalf of USNG.  Prior to October 10, 2013, and therefore for the entire period of this quarterly report on Form 10-Q for the period ended September 30, 2013, USNG paid UBS Securities commissions for executing and clearing trades on behalf of USNG.
	RBC Capital’s primary address is 500 West Madison Street, Suite 2500, Chicago, Illinois 60661.  UBS Securities’ principal business address is 677 Washington Blvd., Stamford, CT 06901. From USNG’s commencement of trading to October 10, 2013, UBS Securities was a futures clearing broker for USNG.  Effective October 10, 2013, RBC Capital became the futures clearing broker for USNG.  Both RBC Capital and UBS Securities are registered in the U.S. with the Financial Industry Regulatory Authority as a broker-dealer and with the CFTC as a FCM. RBC Capital and UBS Securities are members of various U.S. futures and securities exchanges.
	RBC is a large broker-dealer subject to many different complex legal and regulatory requirements. As a result, certain of RBC’s regulators may from time to time conduct investigations, initiate enforcement proceedings and/or enter into settlements with RBC with respect to issues raised in various investigations. RBC complies fully with its regulators in all investigations being conducted and in all settlements it reaches. In addition, RBC is and has been subject to a variety of civil legal claims in various jurisdictions, a variety of settlement agreements and a variety of orders, awards and judgments made against it by courts and tribunals, both in regard to such claims and investigations. RBC complies fully with all settlements it reaches and all orders, awards and judgments made against it.
	RBC has been named as a defendant in various legal actions, including arbitrations, class actions and other litigation including those described below, arising in connection with its activities as a broker-dealer. Certain of the actual or threatened legal actions include claims for substantial compensatory and/or punitive damages or claims for indeterminate amounts of damages. RBC is also involved, in other reviews, investigations and proceedings (both formal and informal) by governmental and self-regulatory agencies regarding RBC’s business, including among other matters, accounting and operational matters, certain of which may result in adverse judgments, settlements, fines, penalties, injunctions or other relief.
	RBC contests liability and/or the amount of damages, as appropriate, in each pending matter. In view of the inherent difficulty of predicting the outcome of such matters, particularly in cases where claimants seek substantial or indeterminate damages or where investigations and proceedings are in the early stages, RBC cannot predict the loss or range of loss, if any, related to such matters; how or if such matters will be resolved; when they will ultimately be resolved; or what the eventual settlement, fine, penalty or other relief, if any, might be. Subject to the foregoing, RBC believes, based on current knowledge and after consultation with counsel, that the outcome of such pending matters will not have a material adverse effect on the consolidated financial condition of RBC.
	On March 11, 2013, the New Jersey Bureau of Securities entered a consent order settling an administrative complaint against RBC, which alleged that RBC failed to follow its own procedures with respect to monthly account reviews and failed to maintain copies of the monthly account reviews with respect to certain accounts that James Hankins Jr. maintained at the firm in violation of N.J.S.A. 49:3-58(a)(2)(xi) and 49:3-59(b).  Without admitting or denying the findings of fact and conclusions of law, RBC consented to a civil monetary penalty of $150,000 (of which $100,000 was suspended as a result of the firm’s cooperation) and to pay disgorgement of $300,000.
	On May 2, 2012, the Massachusetts Securities Division entered a consent order settling an administrative complaint against RBC, which alleged that RBC recommended unsuitable products to its brokerage and advisory clients and failed to supervise its registered representatives’ sales of inverse and leveraged ETFs in violation of Section 204(a)(2) of the Massachusetts Uniform Securities Act (“MUSA”). Without admitting or denying the allegations of fact, RBC consented to permanently cease and desist from violations of MUSA, pay restitution of $2.9 million to the investors who purchased the inverse and leveraged ETFs and pay a civil monetary penalty of $250,000.
	On September 27, 2011, the SEC commenced and settled an administrative proceeding against RBC for willful violations of Sections 17(a)(2) and 17(a)(3) of the 1933 Act for negligently selling the collateralized debt obligations to five Wisconsin school districts despite concerns about the suitability of the product. The firm agreed to pay disgorgement of $6.6 million, prejudgment interest of $1.8 million, and a civil monetary penalty of $22 million.
	On February 24, 2009, the SEC commenced and settled an administrative proceeding against RBC for willful violations of Section 15B(c)(1) of the 1934 Act and Municipal Securities Rulemaking Board Rules G-17, G-20 and G-27, related to municipal expenses in connection with ratings agency trips. The firm was censured and paid a civil monetary penalty of $125,000.
	On June 9, 2009, the SEC commenced and settled a civil action against RBC for willful violations of Section 15(c) of the 1934 Act, in connection with auction rate securities (ARS). The firm agreed to repurchase ARS owned by certain retail customers and to use best efforts to provide ineligible customers opportunities to liquidate ARS, and other ancillary relief.
	Please see RBC’s Form BD for more details.
	RBC Capital will only act as a clearing broker for USNG and as such will be paid commissions for executing and clearing trades on behalf of USNG.  Prior to October 10, 2013, UBS Securities acted only as clearing broker for USNG and as such was paid commissions for executing and clearing trades on behalf of USNG. Neither RBC Capital nor UBS Securities has passed upon the adequacy or accuracy of this quarterly report on Form 10-Q. Neither RBC Capital nor UBS Securities will act in any supervisory capacity with respect to USCF or participate in the management of USCF or USNG.
	Neither RBC Capital nor UBS Securities is affiliated with USNG or USCF. Therefore, neither USCF nor USNG believe that there are any conflicts of interest with RBC Capital and UBS Securities or their trading principals arising from their acting as USNG’s FCM.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2013
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 condensed 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 condensed financial statements. Changes in the unrealized gains or losses between periods are reflected in the condensed statements of operations. USNG earns interest on its assets denominated in U.S. dollars on deposit with the futures commission merchant at the overnight Federal Funds Rate less 32 basis points. In addition, USNG earns income on funds held at the custodian or futures commission merchant at prevailing market rates earned on such investments.
	Investments in over-the-counter total return 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 commodity future, security or index underlying the transaction exceeds or falls short of the offsetting periodic payment obligation, USNG 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 condensed 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 USNG for over-the-counter swap contracts are reflected on the condensed 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
	USNG 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 GAAP, USNG 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. USNG files an income tax return in the U.S. federal jurisdiction, and may file income tax returns in various U.S. states. USNG is not subject to income tax return examinations by major taxing authorities for years before 2009. 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 USNG recording a tax liability that reduces net assets. However, USNG’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. USNG 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 period ended September 30, 2013.
Creations and Redemptions	'
	Creations and Redemptions
	Authorized Purchasers may purchase Creation Baskets or redeem Redemption Baskets only in blocks of 100,000 units at a price equal to the NAV of the units calculated shortly after the close of the core trading session on the NYSE Arca on the day the order is placed.
	USNG receives or pays the proceeds from units sold or redeemed within three business days after the trade date of the purchase or redemption. The amounts due from Authorized Purchasers are reflected in USNG’s condensed statements of financial condition as receivable for units sold, and amounts payable to Authorized Purchasers upon redemption are reflected as payable for units 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 USNG in proportion to the number of units 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 Unit Net Asset Value
	USNG’s per unit 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 units outstanding. USNG 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 Unit	'
	Net Income (Loss) Per Unit
	Net income (loss) per unit is the difference between the per unit NAV at the beginning of each period and at the end of each period. The weighted average number of units outstanding was computed for purposes of disclosing net income (loss) per weighted average unit. The weighted average units are equal to the number of units outstanding at the end of the period, adjusted proportionately for units added and redeemed based on the amount of time the units were outstanding during such period. There were no units held by USCF at September 30, 2013.
Offering Costs	'
	Offering Costs
	Offering costs incurred in connection with the registration of additional units after the initial registration of units are borne by USNG. 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 condensed financial statements were reclassified to conform to the current presentation.
Use of Estimates	'
	Use of Estimates
	The preparation of condensed 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 condensed 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, USNG effected a 4-for-1 reverse unit split and post-split units of USNG began trading on February 22, 2012. The unaudited condensed financial information reported in this quarterly report on Form 10-Q gives effect to the reverse split and the post-split of units as if they had been completed on January 1, 2012.
	The unaudited condensed financial information and pro forma financial information, as well as the historical financial information as of and for the year ended December 31, 2012, was derived from USNG’s historical financial statements and has been audited by Spicer Jeffries LLP. The financial information as of and for the nine months ended September 30, 2013 is unaudited. The condensed financial statements in this quarterly report on Form 10-Q 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.

Financial_Highlights_Tables

Financial Highlights (Tables)	9 Months Ended
	Sep. 30, 2013
Financial Highlights [Abstract]	'
Per Unit Performance Data and Other Supplemental Financial Data	'
	The following table presents per unit performance data and other supplemental financial data for the nine months ended September 30, 2013 and 2012 for the unitholders. This information has been derived from information presented in the condensed financial statements.
		For the nine months ended			For the nine months ended
		September 30, 2013			September 30, 2012
		(Unaudited)			(Unaudited)
	Per Unit Operating Performance:
	Net asset value, beginning of period	$	18.87		$	25.88	*
	Total loss		-0.41			-4.36
	Total expenses		-0.16			-0.16
	Net decrease in net asset value		-0.57			-4.52
	Net asset value, end of period	$	18.3		$	21.36
	Total Return		-3.02	%		-17.47	%
	Ratios to Average Net Assets
	Total income (loss)		3.67	%		-13.49	%
	Expenses excluding management fees**		0.47	%		0.53	%
	Management fees**		0.6	%		0.59	%
	Net income (loss)		2.88	%		-14.34	%
	*      On February 21, 2012, there was a 4-for-1 reverse unit split. The Financial Highlights (Unaudited) have been adjusted for the period shown to reflect the 4-for-1 reverse unit split on a retroactive basis.
	**   Annualized.

Fair_Value_Of_Financial_Instru1

Fair Value Of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2013

Fair Value Disclosures [Abstract]

'

Valuation of USNG’s Securities Using the Fair Value Hierarchy

'

The following table summarizes the valuation of USNG’s securities at September 30, 2013 using the fair value hierarchy:

At September 30, 2013

Total

Level I

Level II

Level III

Short-Term Investments

$

717,602,424

$

717,602,424

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

-47,006,220

-47,006,220

—

—

Over-the-Counter Total Return Swap Contracts

394,058

—

—

394,058

The following table summarizes the valuation of USNG’s securities at December 31, 2012 using the fair value hierarchy:

At December 31, 2012

Total

Level I

Level II

Level III

Short-Term Investments

$

882,586,367

$

882,586,367

$

—

$

—

Exchange-Traded Futures Contracts

United States Contracts

-14,596,843

-14,596,843

—

—

Over-the-Counter Total Return Swap Contracts

-3,470,939

—

—

-3,470,939

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 unobservable inputs (Level III) were used in determining fair value as of September 30, 2013:

Total Return Swap Contracts

Beginning balance as of 12/31/12

$

-3,470,939

Realized gain (loss)*

—

Change in unrealized gain (loss)

3,864,997

Ending balance as of 09/30/13

$

394,058

*

The realized gain (loss) incurred during the nine months ended September 30, 2013 for total return swaps was $(6,290,828).

Following is a reconciliation of assets in which significant unobservable inputs (Level III) were used in determining fair value as of December 31, 2012:

Total Return Swap Contracts

Beginning balance as of 12/31/11

$

-12,805,692

Realized gain (loss)*

—

Change in unrealized gain (loss)

9,334,753

Ending balance as of 12/31/12

$

-3,470,939

*

The realized gain (loss) incurred during the fiscal year ended December 31, 2012 for total return swaps was $(75,525,786).

Fair Value of Derrivative Instruments

'

Effective January 1, 2009, USNG 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

Condensed

Fair Value

Fair Value

Accounted for

Statements of Financial

At September 30, 2013

At December 31, 2012

as Hedging

Condition Location

Instruments

Futures - Commodity Contracts

Assets

$

-47,006,220

$

-14,596,843

Swaps - Commodity Contracts

Assets

394,058

-3,470,939

Effect of Derivative Instruments on the Statements of Operations

'

The Effect of Derivative Instruments on the Condensed Statements of Operations

For the nine months ended

For the nine months ended

September 30, 2013

September 30, 2012

Derivatives not

Location of

Realized

Change in

Realized

Change in

Accounted for

Gain or (Loss)

Gain or (Loss)

Unrealized

Gain or (Loss)

Unrealized

as Hedging

on Derivatives

on Derivatives

Gain or (Loss)

on Derivatives

Gain or (Loss)

Instruments

Recognized in

Recognized in

on Derivatives

Recognized in

on Derivatives

Income

Income

Recognized in

Income

Recognized in

Income

Income

Futures -

Realized gain (loss) on closed futures positions

$

69,898,707

$

-200,481,655

Commodity Contracts

Change in unrealized gain (loss) on open futures positions

$

-32,409,377

$

109,485,403

Swaps -

Realized gain (loss) on closed swap contracts

$

-6,290,828

$

-64,420,592

Commodity Contracts

Change in unrealized gain (loss) on open swap contracts

$

3,864,997

$

22,100,866

Organization_and_Business_Addi

Organization and Business (Additional Information) (Details) (USD $)	0 Months Ended
	Feb. 21, 2012	Apr. 18, 2007	Apr. 01, 2007	Sep. 30, 2013		Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
			Number	Unit
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'		'	'	'
Number of counterparties with over-the-counter swap transactions	'	'	'	2		'	'	'
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	'	$18.30		$18.87	$21.36	$25.88	[1]
Number of units issued	'	200,000	'	'		'	'	'
Value of unit issued	'	$10,001,000	'	'		'	'	'
Commenced investment operations date	'	18-Apr-07	'	'		'	'	'
Number of registered units	'	'	'	430,100,000		'	'	'
Reverse unit split ratio	4	'	'	'		'	'	'
Pre-split units of USNG automatically exchanged for one post-split unit	4	'	'	'		'	'	'
Committee for Uniform Securities Identification Procedures (CUSIP)	'912318201	'	'	'		'	'	'
Open Futures Contracts, Long [Member] | United States [Member] | NYMEX Natural Gas Futures NG November 2013 contracts, expiring october 2013 [Member]	'	'	'	'		'	'	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'		'	'	'
Number of contracts	'	'	'	13,580		'	'	'
Open Futures Contracts, Long [Member] | United States [Member] | NYMEX Natural Gas Futures NN November 2013 contracts, expiring october 2013 [Member]	'	'	'	'		'	'	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'		'	'	'
Number of contracts	'	'	'	9,952		'	'	'
Open Futures Contracts, Long [Member] | United States [Member] | ICE Natural Gas Futures LD1 H August 2013 contracts, expiring August 2013 [Member]	'	'	'	'		'	'	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'		'	'	'
Number of contracts	'	'	'	29,993		'	'	'
Open Futures Contracts, Long [Member] | Foreign [Member] | NYMEX Natural Gas Futures NG November 2013 contracts, expiring october 2013 [Member]	'	'	'	'		'	'	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'		'	'	'
Number of contracts	'	'	'	13,580		'	'	'
Open Futures Contracts, Long [Member] | Foreign [Member] | NYMEX Natural Gas Futures NN November 2013 contracts, expiring october 2013 [Member]	'	'	'	'		'	'	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'		'	'	'
Number of contracts	'	'	'	9,952		'	'	'
Prior to Reverse Split [Member]	'	'	'	'		'	'	'
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]	'	'	'	'		'	'	'
Net Asset Value Per Unit	5.51	'	'	'		'	'	'
Number of units issued	174,297,828	'	'	'		'	'	'
Outstanding 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	'	'	'		'	'	'
Number of units issued	43,574,457	'	'	'		'	'	'
Outstanding units	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	'	'	'	53,525	[2]	'	'	'
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 unit split. The Financial Highlights (Unaudited) have been adjusted for the period shown to reflect the 4-for-1 reverse unit split on a retroactive basis.
[2]	Collateral amounted to $130,185,922 on open futures contracts.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Additional Information) (Details)	0 Months Ended			9 Months Ended
	Feb. 21, 2012	Feb. 21, 2012	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013
	Unit			Maximum [Member]	Redemption Baskets [Member]
Significant Accounting Policies [Line Items]	'	'	'	'	'
Basis points subtracted from overnight Federal Funds Rate	'	'	32.00%	'	'
Number of units per basket	'	'	'	'	100,000
Cash equivalents maturity period	'	'	'	'6 months	'
Reverse unit split ratio	4	4	'	'	'

Fees_Paid_by_Fund_and_Related_

Fees Paid by Fund and Related Party Transactions (Additional Information) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Fees Paid and Related Party Transactions [Line Items]	'	'
USCF Management Fee	'USNG 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.	'
Percentage of average daily net assets of $1,000,000,000 or less, paid monthly	0.60%	'
Average daily net assets	$1,000,000,000	'
Percentage of average daily net assets greater than $1,000,000,000, paid monthly	0.50%	'
Fee percentage	0.02%	'
Assets basis for determining fee percentage	'on all net assets	'
Licensing fee incurred	108,358	110,617
Estimated investor tax reporting cost	1,600,000	'
USNG and the Related Public Funds [Member]	'	'
Fees Paid and Related Party Transactions [Line Items]	'	'
Estimated directors fees and expenses	560,625	'
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]	'	'
Combined assets basis for determining 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%	'
Licensing Agreements [Member] | Combined net assets above $1,000,000,000 [Member] | Minimum [Member]	'	'
Fees Paid and Related Party Transactions [Line Items]	'	'
Combined assets basis for determining fee percentage	$1,000,000,000	'

Contracts_and_Agreements_Addit

Contracts and Agreements (Additional Information) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]	'	'	'	'
Fee percentage	'	'	0.02%	'
Annual Fee for custody, fund accounting and fund administration services	'	'	$20,000	'
Brokerage commissions	615,823	848,929	1,814,781	2,799,540
Ratio of expense to Average Net Assets	'	'	0.25%	0.38%
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	'
Rebalancing Investments Transaction [Member]	'	'	'	'
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]	'	'	'	'
Brokerage commissions	'	'	1,540,235	2,370,831
Trades Necessitated By Creation And Redemption Activity [Member]	'	'	'	'
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]	'	'	'	'
Brokerage commissions	'	'	274,546	428,709
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	'	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 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	1,000,000,000	'	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] | Minimum [Member]	'	'	'	'
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]	'	'	'	'
Base amount for determining fee percentage	500,000,000	'	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] | Minimum [Member]	'	'	'	'
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]	'	'	'	'
Base amount for determining fee percentage	1,000,000,000	'	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	'	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%	'
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	'	$3,000,000,000	'

Financial_Instruments_OffBalan1

Financial Instruments, Off-Balance Sheet Risks and Contingencies (Additional Information) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Carrying Amounts and Fair Values of Financial Instruments or Liabilities [Line Items]	'	'	'
Cash collateral from counterparties	$0	'	$5,000,533
Securities collateral from counterparties	1,214,685	'	1,191,737
Collateral posted in cash with respect to its obligations	0	'	16,144,536
Collateral posted in securities with respect to its obligations	1,214,685	'	15,298,350
Cash investments in money market funds	552,614,029	552,614,029	'
Deposits in domestic and foreign financial institutions	$424,814,423	$692,700,192	'

Financial_Highlights_Per_Unit_

Financial Highlights (Per Unit Performance Data and Other Supplemental Financial Data) (Details) (USD $)	9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Apr. 18, 2007
Per Unit Operating Performance:	'		'		'
Net asset value, beginning of period	$18.87		$25.88	[1]	$50
Total loss	($0.41)		($4.36)		'
Total expenses	($0.16)		($0.16)		'
Net decrease in net asset value	($0.57)		($4.52)		'
Net asset value, end of period	$18.30		$21.36		$50
Total Return	-3.02%		-17.47%		'
Ratios to Average Net Assets	'		'		'
Total income (loss)	3.67%		-13.49%		'
Expenses excluding management fees	0.47%	[2]	0.53%	[2]	'
Management fees	0.60%	[2]	0.59%	[2]	'
Net income (loss)	2.88%		-14.34%		'
[1]	On February 21, 2012, there was a 4-for-1 reverse unit split. The Financial Highlights (Unaudited) have been adjusted for the period shown to reflect the 4-for-1 reverse unit split on a retroactive basis.
[2]	Annualized.

Fair_Value_Of_Financial_Instru2

Fair Value Of Financial Instruments (Valuation of Securities Using Fair Value Hierarchy) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Short-Term Investments [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Securities, fair value	$717,602,424	$882,586,367
Exchange-Traded Futures Contracts [Member] | United States [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Securities, fair value	-47,006,220	-14,596,843
Open Over-the-Counter Total Return Swap Contracts [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Securities, fair value	394,058	-3,470,939
Fair Value, Inputs, Level 1 [Member] | Short-Term Investments [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Securities, fair value	717,602,424	882,586,367
Fair Value, Inputs, Level 1 [Member] | Exchange-Traded Futures Contracts [Member] | United States [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Securities, fair value	-47,006,220	-14,596,843
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	$394,058	($3,470,939)

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 $)	3 Months Ended		9 Months Ended				12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Dec. 31, 2012
					Total Return Swap Contracts [Member]		Total Return Swap Contracts [Member]
Total Return Swap Contracts	'	'	'	'	'		'
Beginning balance	'	'	'	'	($3,470,939)		($12,805,692)
Realized gain (loss)	-14,494,336	21,863,449	-6,290,828	-64,420,592	0	[1]	0	[2]
Change in unrealized gain (loss)	11,245,517	-1,242,090	3,864,997	22,100,866	3,864,997		9,334,753
Ending balance	'	'	'	'	$394,058		($3,470,939)
[1]	The realized gain (loss) incurred during the nine months ended September 30, 2013 for total return swaps was $(6,290,828).
[2]	The realized gain (loss) incurred during the fiscal year ended December 31, 2012 for total return swaps was $(75,525,786).

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 $)	3 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Dec. 31, 2012
					Total Return Swap [Member]	Total Return Swap [Member]
Total Return Swap Contracts	'	'	'	'	'	'
Realized gain (loss)	($14,494,336)	$21,863,449	($6,290,828)	($64,420,592)	$6,290,828	$75,525,786

Fair_Value_Of_Financial_Instru5

Fair Value Of Financial Instruments (Fair Value of Derivative Instruments) (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Futures - Commodity Contracts [Member] | Assets [Member]	'	'
Fair Value of Financial Instruments [Line Items]	'	'
Derivatives not Accounted for as Hedging Instruments	($47,006,220)	($14,596,843)
Swaps - Commodity Contracts [Member] | Assets - Unrealized Appreciation (Depreciation) [Member]	'	'
Fair Value of Financial Instruments [Line Items]	'	'
Derivatives not Accounted for as Hedging Instruments	$394,058	($3,470,939)

Fair_Value_Of_Financial_Instru6

Fair Value Of Financial Instruments (Effect of Derivative Instruments on Condensed Statements of Operations) (Details) (Commodity Contracts [Member], USD $)	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Futures - Commodity Contracts [Member] | Realized gain (loss) on closed futures positions [Member]	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'
Realized Gain or (Loss) on Derivatives Recognized in Income	$69,898,707	($200,481,655)
Futures - Commodity Contracts [Member] | Change in unrealized gain (loss) on open futures positions [Member]	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income	-32,409,377	109,485,403
Swaps - Commodity Contracts [Member] | Realized gain (loss) on closed swap contracts [Member]	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'
Realized Gain or (Loss) on Derivatives Recognized in Income	-6,290,828	-64,420,592
Swaps - Commodity Contracts [Member] | Change in unrealized gain (loss) on open swap contracts [Member]	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income	$3,864,997	$22,100,866

Subsequent_Events_Additional_I

Subsequent Events - (Additional Information) (Details) (USD $)	0 Months Ended		1 Months Ended
	Mar. 11, 2013	2-May-12	Sep. 27, 2011	Feb. 24, 2009
Subsequent Event [Line Items]	'	'	'	'
Loss Contingencies Penalties	$150,000	$250,000	$22,000,000	$125,000
Loss Contingencies Penalties Suspended	100,000	'	'	'
Loss Contingencies Disgorgement	300,000	'	6,600,000	'
Loss Contingencies Restitution	'	2,900,000	'	'
Loss Contingency Pre Judgment Damages Awarded Value	'	'	$1,800,000	'