Condensed Schedule of Investments (USD $)		3 Months Ended						3 Months Ended				3 Months Ended
	Mar. 31, 2013 Open Over-the-Counter Total Return Swap Contracts [Member]	Mar. 31, 2013 Open Over-the-Counter Total Return Swap Contracts [Member] Swap Agreement to Receive Return on the Custom Natural Gas Index (UNG) - Excess Return [Member]		Mar. 31, 2013 Open Over-the-Counter Total Return Swap Contracts [Member] Swap Agreement to Receive Return on the NYMEX Henry Hub Natural Gas Futures Contract [Member]		Mar. 31, 2013 Open Cleared Swap and Futures Contracts [Member] Open Cleared Swap Contracts, Long [Member] Foreign [Member] ICE Natural Gas LD1 H Cleared Swap May 2013 contracts, expiring April 2013 [Member] Contracts	Mar. 31, 2013 Open Cleared Swap and Futures Contracts [Member] Open Futures Contracts, Long [Member] United States [Member] Contracts	Mar. 31, 2013 Open Cleared Swap and Futures Contracts [Member] Open Futures Contracts, Long [Member] United States [Member] NYMEX Natural Gas Futures NG May 2013 contracts, expiring April 2013 [Member] Contracts	Mar. 31, 2013 Open Cleared Swap and Futures Contracts [Member] Open Futures Contracts, Long [Member] United States [Member] NYMEX Natural Gas Futures NN May 2013 contracts, expiring April 2013 [Member] Contracts	Mar. 31, 2013 Cash Equivalents [Member]	Mar. 31, 2013 Cash Equivalents [Member] United States [Member] US Treasury Securities [Member]	Mar. 31, 2013 Cash Equivalents [Member] United States [Member] US Treasury Securities [Member] U.S. Treasury Bills, 0.05%, 5/02/2013 [Member]		Mar. 31, 2013 Cash Equivalents [Member] United States [Member] US Treasury Securities [Member] U.S. Treasury Bills,0.08%, 5/30/2013 [Member]	Mar. 31, 2013 Cash Equivalents [Member] United States [Member] Money Market Funds [Member]	Mar. 31, 2013 Cash Equivalents [Member] United States [Member] Money Market Funds [Member] Fidelity Institutional Government Portfolio - Class I [Member]	Mar. 31, 2013 Cash Equivalents [Member] United States [Member] Money Market Funds [Member] Goldman Sachs Financial Square Funds - Government Fund - Class FS [Member]	Mar. 31, 2013 Cash Equivalents [Member] United States [Member] Money Market Funds [Member] Morgan Stanley Institutional Liquidity Fund - Government Portfolio [Member]	Mar. 31, 2013 Cash Equivalents [Member] United States [Member] Money Market Funds [Member] Wells Fargo Advantage Government Money Market Fund - Class I [Member]
Contracts Notional Amount		$ 121,986,086	[1]	$ 87,670,232	[1]
Number of contracts						38,192	54,101	5,957	9,952
Principal Amount												100,000,000		95,500,000		101,608,278	150,508,087	200,495,952	100,001,712
Unrealized Loss on Open Commodity Contracts						22,364,360	33,713,180	5,117,600	6,231,220
Market Value		(1,326,098)		5,410,413						748,097,620	195,483,591	99,995,330		95,488,261	552,614,029	101,608,278	150,508,087	200,495,952	100,001,712
Unrealized Gain (Loss)	$ 4,084,315	$ (1,326,098)		$ 5,410,413
% of Partners' Capital						2.39%	3.60%	0.55%	0.66%	79.78%	20.85%	10.67%		10.18%	58.93%	10.84%	16.05%	21.38%	10.66%
Termination Dates		4/23/2013		8/31/2013		April 2013		April 2013	April 2013			5/02/2013	[2]	5/30/2013

[1] The aggregate notional amount of USNG's over-the-counter swap transactions represented 20.24% of USNG's total assets as of March 31, 2013.

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