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ORGANIZATION AND BUSINESS (Additional Information) (Details) |  | 1 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Jan. 04, 2018 $ / shares shares | Apr. 30, 2007 | Apr. 18, 2007 USD ($) $ / shares shares | Mar. 31, 2019 Contracts $ / shares $ / Unit | Dec. 31, 2018 $ / shares | Mar. 31, 2018 $ / shares | Dec. 31, 2017 $ / shares | [1]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets | $ / Unit |  |  |  |  | 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 | $ / shares |  |  |  |  | $ 23.42 | $ 24.35 | $ 22.54 | $ 23.34
Number of units issued | shares |  |  |  | 200,000 |  |  |  |
Value of unit issued | $ |  |  |  | $ 10,001,000 |  |  |  |
Number of registered units |  |  |  |  | 2,080,000,000 |  |  |
Committee For Uniform Securities Identification Procedure Cusip |  | CUSIP number for UNG’s shares changed to 912318300 |  |  |  |  |  |
Operations Commenced Date |  |  |  | Apr. 18, 2007 |  |  |  |
United States [Member] | Open Futures Contracts Long [Member] |  |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Number of Contracts | Contracts | [2] |  |  |  | 13,324 |  |  |
United States [Member] | NYMEX Natural Gas Futures Contracts [Member] | Open Futures Contracts Long [Member] |  |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Number of Contracts | Contracts |  |  |  |  | 8,324 |  |  |
United States [Member] | ICE Natural Gas Futures LD1 H Contracts [Member] | Open Futures Contracts Long [Member] |  |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Number of Contracts | Contracts |  |  |  |  | 5,000 |  |  |
Prior to Reverse Split [Member] |  |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Net Asset Value Per Unit | $ / shares |  | $ 5.69 |  | $ 50.00 |  |  |  |
Issued units | shares |  | 97,466,476 |  |  |  |  |  |
Stockholders' Equity, Reverse Stock Split |  | 1-for-4 reverse share split |  |  |  |  |  |
Following Reverse Split [Member] |  |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Net Asset Value Per Unit | $ / shares |  | $ 22.76 |  |  |  |  |  |
Capital Units, Outstanding | shares |  | 24,366,619 |  |  |  |  |  |
Creation Baskets [Member] |  |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Number of units per basket | $ / Unit |  |  |  |  | 100,000 |  |  |
Redemption Baskets [Member] |  |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |  |
Number of units per basket | $ / Unit |  |  |  |  | 100,000 |  |  |
[1] | On January 4, 2018, there was a 1-for-4 reverse share split. Historical shares outstanding, net asset value per share and market value per share have been adjusted for the period shown to reflect the 1-for-4 reverse share split on a retroactive basis.
[2] | Collateral amounted to $77,620,675 on open futures contracts.

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