| N-2 | 6 Months Ended |
| Jun. 30, 2023 shares | |
| Cover [Abstract] | |
| Entity Central Index Key | 0001080720 |
| Amendment Flag | false |
| Document Type | N-CSRS |
| Entity Registrant Name | The Gabelli Utility Trust |
| Document Period End Date | Jun. 30, 2023 |
| General Description of Registrant [Abstract] | |
| Investment Objectives and Practices [Text Block] | Investment Objective (Unaudited) The Fund’s primary investment objective is long term growth of capital and income. The Fund will invest 80% of its assets, under normal market conditions, in common stocks and other securities of foreign and domestic companies involved in providing products, services, or equipment for (i) the generation or distribution of electricity, gas, and water and (ii) telecommunications services or infrastructure operations. |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Capital Stock [Table Text Block] | 6. Capital. Transactions in shares of beneficial interest were as follows: Six Months Ended Year Ended Shares Amount Shares Amount Net increase in net assets from common shares issued in rights offering — — 9,133,529 $ 50,234,410 Net increase in net assets from common shares issued upon reinvestment of distributions 583,472 $ 3,908,254 1,011,565 6,983,503 Net increase 583,472 $ 3,908,254 10,145,094 $ 57,217,913 The Fund’s Declaration of Trust, as amended, authorizes the issuance of an unlimited number of shares of $0.001 par value Preferred Shares. The Preferred Shares are senior to the common shares and result in the financial leveraging of the common shares. Such leveraging tends to magnify both the risks and opportunities to common shareholders. Dividends on the Preferred Shares are cumulative. The Fund is required by the 1940 Act and by the Statement of Additional Information to meet certain asset coverage tests with respect to the Preferred Shares. If the Fund fails to meet these requirements and does not correct such failure, the Fund may be required to redeem, in part or in full, Series B and Series C Preferred Shares at redemption prices of $25,000 and $25, respectively, per share plus an amount equal to the accumulated and unpaid dividends whether or not declared on such shares in order to meet these requirements. Additionally, failure to meet the foregoing asset coverage requirements could restrict the Fund’s ability to pay dividends to common shareholders and could lead to sales of portfolio securities at inopportune times. The income received on the Fund’s assets may vary in a manner unrelated to the fixed and variable rates, which could have either a beneficial or detrimental impact on investment income and gains available to common shareholders. The Fund may redeem at any time, in whole or in part, the Series B Preferred and Series C Preferred at their respective per share redemption of $25,000 and $25. In addition, the Board has authorized the repurchase of the Series C Preferred in the open market at prices less than the $25 liquidation value per share. During the six months ended June 30, 2023, the Fund did not repurchase any Series C Preferred; during the year ended December 31, 2022, the Fund repurchased and retired 12,774 of the Series C Preferred Shares in the open market at an investment of $303,012, at an average discount of approximately 5.2% from its liquidation preference; during the six months ended June 30, 2023 and the year ended December 31, 2022, the Fund did not repurchase any shares of Series B Preferred. On January 31, 2022, the Fund redeemed all Series A Preferred at the Redemption Price of $25.13671875 per share, which consisted of the liquidation preference of $25.00 plus $0.13671875 per share representing accumulated but unpaid dividends and distributions to the redemption date of January 31, 2022. For Series B Preferred Shares, the dividend rates are typically set by an auction process that is generally held every seven days, and are typically expected to vary with short term interest rates. Since February 2008, the number of Series B Preferred Shares subject to bid orders by potential holders has been less than the number of shares of Series B sell orders. Holders that have submitted sell orders have not been able to sell any or all of the Series B Preferred Shares for which they have submitted sell orders. Therefore the weekly auctions have failed, and the dividend rate has been the maximum rate. The current maximum rate for Series B Preferred Shares is 200 basis points greater than the seven day ICE LIBOR rate on the date of such auction. Since December 31, 2021, the seven day ICE LIBOR rate has ceased to be published and is no longer representative. Because the Series B Preferred Shares have no other effective alternative rate setting provision, a last resort fallback of fixing this LIBOR based reference rate at its last published rate applies. The last published seven day ICE LIBOR rate was 0.076%, which results in a fixed maximum rate for Series B Preferred Shares of 2.076% for all failed auctions after December 31, 2021. In the absence of successful future auctions that establish dividend rates based on prevailing short term interest rates, this result could lead to divergent and unexpected economic results for the Fund and holders of the Series B Preferred Shares since the rates payable on the Series B Preferred Shares are no longer likely to be representative of prevailing market rates. Existing Series B Preferred shareholders may submit an order to hold, bid, or sell such shares on each auction date, or trade their shares in the secondary market. The Fund has the authority to purchase its Series B auction market preferred shares through negotiated private transactions. The Fund is not obligated to purchase any dollar amount or number of auction market preferred shares, and the timing and amount of any auction market preferred shares purchased will depend on market conditions, share price, capital availability, and other factors. The Fund is not soliciting holders to sell these shares nor recommending that holders offer them to the Fund. Any offers can be accepted or rejected in the Fund’s discretion. The following table summarizes Cumulative Preferred Shares information: Series Issue Date Authorized Number of Net Proceeds 2023 Dividend Dividend Accrued B Auction Market July 31, 2003 1,000 900 $ 24,590,026 2.076% 2.076 % $ 3,839 C 5.375% May 31, 2016 2,000,000 1,987,226 $ 48,142,029 Fixed Rate 5.375 % $ 37,088 The holders of Preferred Shares generally are entitled to one vote per share held on each matter submitted to a vote of shareholders of the Fund and will vote together with holders of common stock as a single class. The holders of Preferred Shares voting together as a single class also have the right currently to elect two Trustees and under certain circumstances are entitled to elect a majority of the Board of Trustees. In addition, the affirmative vote of a majority of the votes entitled to be cast by holders of all outstanding shares of the preferred shares, voting as a single class, will be required to approve any plan of reorganization adversely affecting the preferred shares, and the approval of two-thirds of each class, voting separately, of the Fund’s outstanding voting stock must approve the conversion of the Fund from a closed-end to an open-end investment company. The approval of a majority (as defined in the 1940 Act) of the outstanding preferred shares and a majority (as defined in the 1940 Act) of the Fund’s outstanding voting securities are required to approve certain other actions, including changes in the Fund’s investment objectives or fundamental investment policies. On March 10, 2022, the Fund distributed one transferable right for each of the 63,934,698 common shares outstanding on that date. Seven rights were required to purchase one additional common share at the subscription price of $5.50 per share. On April 20, 2022, the Fund issued 9,133,529 common shares receiving net proceeds of $49,849,194, after the deduction of offering expenses of $385,216. The NAV of the Fund increased by $0.16 per share on the day the additional shares were issued due to the additional shares being issued above NAV. The fund has an effective shelf registration authorizing an additional $138 million of common or preferred shares. |
| Common Stocks [Member] | |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Outstanding Security, Not Held [Shares] | 74,526,620 |
| Cumulative Preferred Stocks [Member] | |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Security Voting Rights [Text Block] | The holders of Preferred Shares generally are entitled to one vote per share held on each matter submitted to a vote of shareholders of the Fund and will vote together with holders of common stock as a single class. The holders of Preferred Shares voting together as a single class also have the right currently to elect two Trustees and under certain circumstances are entitled to elect a majority of the Board of Trustees. In addition, the affirmative vote of a majority of the votes entitled to be cast by holders of all outstanding shares of the preferred shares, voting as a single class, will be required to approve any plan of reorganization adversely affecting the preferred shares, and the approval of two-thirds of each class, voting separately, of the Fund’s outstanding voting stock must approve the conversion of the Fund from a closed-end to an open-end investment company. The approval of a majority (as defined in the 1940 Act) of the outstanding preferred shares and a majority (as defined in the 1940 Act) of the Fund’s outstanding voting securities are required to approve certain other actions, including changes in the Fund’s investment objectives or fundamental investment policies. On March 10, 2022, the Fund distributed one transferable right for each of the 63,934,698 common shares outstanding on that date. Seven rights were required to purchase one additional common share at the subscription price of $5.50 per share. On April 20, 2022, the Fund issued 9,133,529 common shares receiving net proceeds of $49,849,194, after the deduction of offering expenses of $385,216. The NAV of the Fund increased by $0.16 per share on the day the additional shares were issued due to the additional shares being issued above NAV. The fund has an effective shelf registration authorizing an additional $138 million of common or preferred shares. |
| Preferred Stock Restrictions, Other [Text Block] | The Fund’s Declaration of Trust, as amended, authorizes the issuance of an unlimited number of shares of $0.001 par value Preferred Shares. The Preferred Shares are senior to the common shares and result in the financial leveraging of the common shares. Such leveraging tends to magnify both the risks and opportunities to common shareholders. Dividends on the Preferred Shares are cumulative. The Fund is required by the 1940 Act and by the Statement of Additional Information to meet certain asset coverage tests with respect to the Preferred Shares. If the Fund fails to meet these requirements and does not correct such failure, the Fund may be required to redeem, in part or in full, Series B and Series C Preferred Shares at redemption prices of $25,000 and $25, respectively, per share plus an amount equal to the accumulated and unpaid dividends whether or not declared on such shares in order to meet these requirements. Additionally, failure to meet the foregoing asset coverage requirements could restrict the Fund’s ability to pay dividends to common shareholders and could lead to sales of portfolio securities at inopportune times. The income received on the Fund’s assets may vary in a manner unrelated to the fixed and variable rates, which could have either a beneficial or detrimental impact on investment income and gains available to common shareholders. The Fund may redeem at any time, in whole or in part, the Series B Preferred and Series C Preferred at their respective per share redemption of $25,000 and $25. In addition, the Board has authorized the repurchase of the Series C Preferred in the open market at prices less than the $25 liquidation value per share. During the six months ended June 30, 2023, the Fund did not repurchase any Series C Preferred; during the year ended December 31, 2022, the Fund repurchased and retired 12,774 of the Series C Preferred Shares in the open market at an investment of $303,012, at an average discount of approximately 5.2% from its liquidation preference; during the six months ended June 30, 2023 and the year ended December 31, 2022, the Fund did not repurchase any shares of Series B Preferred. On January 31, 2022, the Fund redeemed all Series A Preferred at the Redemption Price of $25.13671875 per share, which consisted of the liquidation preference of $25.00 plus $0.13671875 per share representing accumulated but unpaid dividends and distributions to the redemption date of January 31, 2022. For Series B Preferred Shares, the dividend rates are typically set by an auction process that is generally held every seven days, and are typically expected to vary with short term interest rates. Since February 2008, the number of Series B Preferred Shares subject to bid orders by potential holders has been less than the number of shares of Series B sell orders. Holders that have submitted sell orders have not been able to sell any or all of the Series B Preferred Shares for which they have submitted sell orders. Therefore the weekly auctions have failed, and the dividend rate has been the maximum rate. The current maximum rate for Series B Preferred Shares is 200 basis points greater than the seven day ICE LIBOR rate on the date of such auction. Since December 31, 2021, the seven day ICE LIBOR rate has ceased to be published and is no longer representative. Because the Series B Preferred Shares have no other effective alternative rate setting provision, a last resort fallback of fixing this LIBOR based reference rate at its last published rate applies. The last published seven day ICE LIBOR rate was 0.076%, which results in a fixed maximum rate for Series B Preferred Shares of 2.076% for all failed auctions after December 31, 2021. In the absence of successful future auctions that establish dividend rates based on prevailing short term interest rates, this result could lead to divergent and unexpected economic results for the Fund and holders of the Series B Preferred Shares since the rates payable on the Series B Preferred Shares are no longer likely to be representative of prevailing market rates. Existing Series B Preferred shareholders may submit an order to hold, bid, or sell such shares on each auction date, or trade their shares in the secondary market. The Fund has the authority to purchase its Series B auction market preferred shares through negotiated private transactions. The Fund is not obligated to purchase any dollar amount or number of auction market preferred shares, and the timing and amount of any auction market preferred shares purchased will depend on market conditions, share price, capital availability, and other factors. The Fund is not soliciting holders to sell these shares nor recommending that holders offer them to the Fund. Any offers can be accepted or rejected in the Fund’s discretion. |
| Outstanding Securities [Table Text Block] | The following table summarizes Cumulative Preferred Shares information: Series Issue Date Authorized Number of Net Proceeds 2023 Dividend Dividend Accrued B Auction Market July 31, 2003 1,000 900 $ 24,590,026 2.076% 2.076 % $ 3,839 C 5.375% May 31, 2016 2,000,000 1,987,226 $ 48,142,029 Fixed Rate 5.375 % $ 37,088 |
| Series B Cumulative Preferred Stock [Member] | |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Outstanding Security, Title [Text Block] | B Auction Market |
| Outstanding Security, Authorized [Shares] | 1,000 |
| Outstanding Security, Not Held [Shares] | 900 |
| Series C Cumulative Preferred Stock [Member] | |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Outstanding Security, Title [Text Block] | C 5.375% |
| Outstanding Security, Authorized [Shares] | 2,000,000 |
| Outstanding Security, Not Held [Shares] | 1,987,226 |
