| N-2 | 6 Months Ended |
| Jun. 30, 2023 shares | |
| Cover [Abstract] | |
| Entity Central Index Key | 0001282957 |
| Amendment Flag | false |
| Document Type | N-CSRS |
| Entity Registrant Name | The Gabelli Global Utility & Income Trust |
| Document Period End Date | Jun. 30, 2023 |
| General Description of Registrant [Abstract] | |
| Investment Objectives and Practices [Text Block] | Investment Objective and Strategy (Unaudited) The Gabelli Global Utility & Income Trust is a diversified, closed-end management investment company. The Fund’s investment objective is to seek a consistent level of after-tax total return for its investors with an emphasis on tax advantaged dividend income under current tax law. Under normal market conditions, the Fund invests at least 80% of its assets in equity securities and income producing securities of domestic and foreign companies involved in the utilities industry and other industries that are expected to pay periodic dividends. |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Capital Stock [Table Text Block] | 6. Capital. On May 12, 2022, the Fund distributed one transferable right for each of the 5,377,458 common shares outstanding on that date. Four rights were required to purchase one additional common share at the subscription price of $16 per share. On June 30, 2022, the Fund issued 591,453 common shares receiving net proceeds of $9,148,248 after the deduction of estimated offering expenses of $315,000. The NAV of the Fund decreased by $0.15 per share on the day the additional shares were issued due to the shares being issued below NAV. For the six months ended June 30, 2023 and the year ended December 31, 2022, transactions in common stock were as follows: Six Months Ended Year Ended Shares Amount Shares Amount Increase in net assets from common shares issued in offering — — 591,453 $ 9,463,248 Net increase in net assets from common shares issued upon reinvestment of distributions — — 1,628 $ 31,744 Net increase — — 593,081 $ 9,494,992 The Fund’s Declaration of Trust, as amended, authorizes the issuance of an unlimited number of shares of $0.001 par value Preferred Shares. 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 Series A and Series B Preferred are cumulative and the liquidation value is $50 per share. The Fund is required by the 1940 Act and by the Fund’s Statement of Preferences 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, the Series A and Series B Preferred Shares at the redemption price of $50 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 net investment income and gains available to common shareholders. As of June 30, 2023, the Fund had an effective shelf registration authorizing the issuance of $141 million in common or preferred shares. The Series A Preferred has an annual dividend rate of 3.80%. The Fund may redeem at any time all or any part of the Series A Preferred at the liquidation value plus accumulated and unpaid dividends. During the six months ended June 30, 2023, and the year ended December 2022, the Fund repurchased and retired 492 and 11,442 of the Series A Preferred Shares in the open market at investments of $22,893 and $534,861 and at average discounts of approximately 6.96% and 6.53% from its liquidation preference. The Series B Preferred pay distributions at the annualized rate of 4.00% on the $50 per share liquidation value. The Series B preferred may be put back to the Fund during the thirty day period prior to December 26, 2023 at the per share liquidation value of $50 plus any accumulated and unpaid dividends. Commencing on December 26, 2023, the Fund, at its option, may redeem the remaining Series B Preferred on the same terms. On December 28, 2021, the Fund redeemed and retired 51,968 shares of Series B Preferred where shareholders properly submitted for redemption during the 30 day period prior to December 26, 2021 at their liquidation value of $50 per share plus any accumulated and unpaid dividends. On January 8, 2022, the fund repurchased 1,048 shares of Series B Preferred at their liquidation preference of $50 per share. The following table summarizes Cumulative Preferred Stock information: Series Issue Date Authorized Number of Shares Outstanding at 6/30/2023 Net Proceeds 2023 Rate Range Dividend Rate at 6/30/2023 Accrued Dividends at 6/30/2023 A 3.800% April 11, 2013 1,200,000 20,595 $ 70,286,465 Fixed Rate 3.800 % $ 543 B 4.000% December 19, 2018 1,370,433 1,205,013 81,988,557 Fixed Rate 4.000 % $ 33,473 The holders of Preferred Shares generally are entitled to one vote per share held on each matter submitted to a vote of stockholders 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 stock, 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. |
| Common Stocks [Member] | |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Outstanding Security, Not Held [Shares] | 5,968,911 |
| 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 stockholders 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 stock, 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. |
| 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. 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 Series A and Series B Preferred are cumulative and the liquidation value is $50 per share. The Fund is required by the 1940 Act and by the Fund’s Statement of Preferences 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, the Series A and Series B Preferred Shares at the redemption price of $50 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 net investment income and gains available to common shareholders. As of June 30, 2023, the Fund had an effective shelf registration authorizing the issuance of $141 million in common or preferred shares. |
| Outstanding Securities [Table Text Block] | The following table summarizes Cumulative Preferred Stock information: Series Issue Date Authorized Number of Shares Outstanding at 6/30/2023 Net Proceeds 2023 Rate Range Dividend Rate at 6/30/2023 Accrued Dividends at 6/30/2023 A 3.800% April 11, 2013 1,200,000 20,595 $ 70,286,465 Fixed Rate 3.800 % $ 543 B 4.000% December 19, 2018 1,370,433 1,205,013 81,988,557 Fixed Rate 4.000 % $ 33,473 |
| Series A Cumulative Preferred Stock [Member] | |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Preferred Stock Restrictions, Other [Text Block] | The Series A Preferred has an annual dividend rate of 3.80%. The Fund may redeem at any time all or any part of the Series A Preferred at the liquidation value plus accumulated and unpaid dividends. During the six months ended June 30, 2023, and the year ended December 2022, the Fund repurchased and retired 492 and 11,442 of the Series A Preferred Shares in the open market at investments of $22,893 and $534,861 and at average discounts of approximately 6.96% and 6.53% from its liquidation preference. |
| Outstanding Security, Title [Text Block] | A 3.800% |
| Outstanding Security, Authorized [Shares] | 1,200,000 |
| Outstanding Security, Not Held [Shares] | 20,595 |
| Series B Cumulative Preferred Stock [Member] | |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Preferred Stock Restrictions, Other [Text Block] | The Series B Preferred pay distributions at the annualized rate of 4.00% on the $50 per share liquidation value. The Series B preferred may be put back to the Fund during the thirty day period prior to December 26, 2023 at the per share liquidation value of $50 plus any accumulated and unpaid dividends. Commencing on December 26, 2023, the Fund, at its option, may redeem the remaining Series B Preferred on the same terms. |
| Outstanding Security, Title [Text Block] | B 4.000% |
| Outstanding Security, Authorized [Shares] | 1,370,433 |
| Outstanding Security, Not Held [Shares] | 1,205,013 |
