XML 34 R19.htm IDEA: XBRL DOCUMENT
v3.8.0.1

FINANCIAL HIGHLIGHTS (Tables) | 9 Months Ended
--- | ---
Sep. 30, 2017
Financial Highlights [Abstract] |
Per Unit Performance Data and Other Supplemental Financial Data | The following table presents per share performance data and other supplemental financial data for the nine months ended September 30, 2017 and 2016 for the shareholders. 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, 2017 |  |  | September 30, 2016 |
|  | (Unaudited) |  |  | (Unaudited) |
Per Share Operating Performance: |  |  |  |  |  |  |  |
Net asset value, beginning of period |  | $ | 9.29 |  |  | $ | 8.69 |
Total income (loss) |  |  | (2.68) |  |  |  | (0.30) |
Total expenses |  |  | (0.07) |  |  |  | (0.06) |
Net increase (decrease) in net asset value |  |  | (2.75) |  |  |  | (0.36) |
Net asset value, end of period |  | $ | 6.54 |  |  | $ | 8.33 |
Total Return |  |  | (29.60) | % |  |  | (4.14) | %
Ratios to Average Net Assets |  |  |  |  |  |  |  |
Total income (loss) |  |  | (31.58) | % |  |  | 3.98 | %
Management fees* |  |  | 0.60 | % |  |  | 0.60 | %
Expenses excluding management fees* |  |  | 0.68 | % |  |  | 0.54 | %
Net income (loss) |  |  | (32.54) | % |  |  | 3.13 | %
| * | Annualized.

X
- References No definition available. + Details
Name: | ung_FinancialHighlightsAbstract
Namespace Prefix: | ung_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Per Unit Performance Data and Other Supplemental Financial Data [Table Text Block] + References No definition available. + Details
Name: | ung_PerUnitPerformanceDataAndOtherSupplementalFinancialDataTableTextBlock
Namespace Prefix: | ung_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration