| N-2 | 12 Months Ended |
| Mar. 31, 2024 | |
| Cover [Abstract] | |
| Entity Central Index Key | 0000030125 |
| Amendment Flag | false |
| Document Type | N-CSR |
| Entity Registrant Name | Insight Select Income Fund |
| General Description of Registrant [Abstract] | |
| Investment Objectives and Practices [Text Block] | INVESTMENT OBJECTIVE AND POLICIES Investment Objective There have been no changes in the Fund’s investment objective since the prior disclosure date. The Fund’s investment objective is to seek a high rate of return, primarily from interest income and trading activity, from a portfolio principally consisting of debt securities. The Fund’s investment objective may be changed by the Board of Trustees of the Fund without shareholder approval. There can be no assurance that the Fund will achieve its objective. Principal Investment Strategies and Policies There have been no material changes in the Fund’s Principal Investment Strategies and Policies since the prior disclosure that have not been approved by shareholders. Under normal market conditions, the Fund invests at least 80% of its Managed Assets (defined below) in debt securities (the “80% Policy”). Seventy-five percent of the Fund’s Managed Assets will be invested in following types of higher quality, non-convertible debt securities (including bonds and debentures): • debt securities (with or without attached warrants) rated, at the time of purchase, within the four highest grades as determined by a nationally recognized statistical ratings organization, such as Moody’s (i.e., Aaa, Aa, A or Baa) or Standard & Poor’s (i.e., AAA, AA, A or BBB) (collectively, the “NRSRO Rated Securities”); • short-term debt securities (“debentures”) which are not NRSRO Rated Securities, but which are obligations of issuers having, at the time of purchase, any NRSRO Rated Securities and which debentures are considered by the Adviser to have an investment quality comparable to NRSRO Rated Securities; • obligations of the United States Government, its agencies or instrumentalities; and • bank debt securities (with or without attached warrants) which, although not NRSRO Rated Securities, are considered by the Adviser to have an investment quality comparable NRSRO Rated Securities. “Managed Assets” means net assets, plus the proceeds from borrowings and the issuance of senior securities for investment purposes. The ratings criteria described above apply at the time of acquisition of the security. In the event that a security held in this portion of the Fund’s portfolio is downgraded to below Baa or BBB, the Fund will no longer include such security in this portion of the Fund’s portfolio. The Fund does not expect that the value of warrants in this part of its portfolio will often be significant. The balance of the Fund’s investments is expected to be principally in debt securities that do not meet the standards described above and in preferred stocks which may be convertible or may be accompanied by warrants or other equity securities. Any securities in this part of the portfolio may be of lower quality and may not be rated by any NRSRO. Fixed-income securities rated below Baa/BBB are considered below investment grade (“high yield” or “junk” bonds). All warrants remaining after sale of the securities to which they were attached and common stocks acquired on conversion or exercise of warrants will be included in this part of the Fund’s portfolio. Any such warrants or common stocks may be held until a long-term holding period has been established for tax purposes, after which they ordinarily will be sold. From time to time, the Fund may also purchase futures contracts, including interest rate futures, (“futures contracts”) and related options thereon, to hedge the Funds interest rate risk and/or duration risk. A futures contract sale creates an obligation by the Fund, as a seller, to deliver the specific type of instrument called for in the contract at a specified future time for a specified price. A futures contract purchase creates an obligation by the Fund, as purchaser, to take delivery of the specific type of financial instrument at a specified future time at a specified price. The Fund has established a credit facility secured by a portion of the Fund’s portfolio investments from which the Fund will be able to borrow money to be invested pursuant to the Fund’s investment strategy. The Fund is permitted to borrow up to the limit permitted under the 1940 Act. The Fund focuses on a relative value strategy. The Fund seeks to identify opportunities to purchase securities with high risk-adjusted yields across various fixed income sectors in order to maintain and increase the Fund’s income, and therefore the Fund’s dividend payment. In constructing the Fund’s portfolio, the Adviser relies primarily on proprietary, internally-generated credit research. This credit research focuses on both industry/sector analysis and detailed individual security selection. The fund’s Adviser seeks to identify investment opportunities for the Fund based on its evaluation of the relative value of securities. The Adviser analyzes individual issuer credit risk based on factors such as management depth and experience, competitive advantage, market and product position and overall financial strength. The Adviser may supplement its internal research with external, third-party credit research and related credit tools. The Fund’s average duration is expected to be near the duration of the Bloomberg U.S. Credit Index which is the Fund’s benchmark. On March 31, 2024, the Fund’s duration was 7.07 years and the duration of the Fund’s benchmark was 6.84 years. The Adviser expects that the Fund’s duration will remain between 4 and 8 years; however, the Fund’s duration may be lengthened or shortened depending on market conditions. Duration is a measure of the expected life of a debt security that is used to determine the sensitivity of the security’s price to changes in interest rates. Generally, the longer the Fund’s duration, the more sensitive the Fund will be to changes in interest rates. For example, the price of a fixed income fund with a duration of five years would be expected to fall approximately 5% if interest rates rose 1%. The type of fixed-income securities in which the Fund may invest include: (i) securities issued or guaranteed by the U.S. government, its agencies or government sponsored enterprises (U.S. government securities); (ii) corporate debt securities, including bonds, notes, debentures, convertible securities, preferred stock and corporate commercial paper; issued by U.S. and non-U.S. corporations and other entities, such as master limited partnerships; (iii) mortgage-related securities; (iv) asset-backed securities; (v) inflation indexed bonds issued by governments or corporations; (vi) structured notes (i.e., specially designed debt instruments whose return is determined by reference to an index or security); (vii) bank loans, including participations and assignments; (viii) delayed funding loans and revolving credit facilities; (ix) bank certificates of deposit, fixed time deposits and bankers’ acceptances; (x) repurchase agreements and reverse repurchase agreements; (xi) debt securities issued by states or local governments or their agencies, authorities or other government sponsored enterprises (municipal securities); (xii) obligations of foreign governments or their subdivisions, agencies or government sponsored enterprises; and (xiii) obligations of international agencies or supranational entities. These securities may have all types of interest rate payment and reset terms, including fixed rate, adjustable rate, floating rate, zero coupon, contingent, deferred, payment in kind and auction rate features. The Fund’s 80% policy set forth above may be changed upon 60 days written notice to shareholders. When the Adviser believes that market conditions make it appropriate, for temporary, defensive purposes the Fund may invest up to 100% of its assets in cash, high quality short-term money market instruments, and in bills, notes or bonds issued by the U.S. Treasury Department or by other agencies of the U.S. Government. When the Fund makes investments for defensive purposes, it may not achieve its investment objective. Investment Restrictions The Fund is subject to a number of investment restrictions, some of which are deemed fundamental and may not be changed without the affirmative vote of a majority of the outstanding voting securities of the Fund, and some of which are not fundamental and may be changed by the Fund’s Board. The Fund’s fundamental investment policies may be changed only with the approval of the holders of a “majority of the Fund’s outstanding voting securities,” which, as used in this prospectus, means the lesser of (1) 67% of the Shares represented at a meeting at which more than 50% of the outstanding Shares are present in person or by proxy, or (2) more than 50% of the outstanding Shares. Any investment policy or restriction which involves a maximum percentage of securities or assets is not considered to be violated unless an excess over the percentage occurs immediately after an acquisition of securities or utilization of assets and results therefrom. The Fund’s fundamental policies are set forth below. 1. The Fund will not borrow money, except to the extent permitted under the 1940 Act, as such may be interpreted or modified by regulatory authorities having jurisdiction, from time to time. 2. The Fund will not issue senior securities, except to the extent permitted under the 1940 Act, as such may be interpreted or modified by regulatory authorities having jurisdiction, from time to time. 3. The Fund will not act as an underwriter of securities within the meaning of the Securities Act of 1933, as amended, except to the extent permitted under the 1940 Act, as such may be interpreted or modified by regulatory authorities having jurisdiction, from time to time. 4. The Fund will not “concentrate” its investments in an industry, except to the extent permitted under the 1940 Act, as such may be interpreted or modified by regulatory authorities having jurisdiction, from time to time. 5. The Fund will not purchase or sell real estate, except to the extent permitted under the 1940 Act, as such may be interpreted or modified by regulatory authorities having jurisdiction, from time to time. 6. The Fund will not purchase or sell commodities, except to the extent permitted under the 1940 Act, as such may be interpreted or modified by regulatory authorities having jurisdiction, from time to time. 7. The Fund will not make loans to other persons, except to the extent permitted under the 1940 Act, as such may be interpreted or modified by regulatory authorities having jurisdiction, from time to time. The foregoing policies are fundamental and may not be changed without shareholder approval. The Fund’s policies which are not deemed fundamental and which may be changed by the Board without shareholder approval are set forth below: 1. The Fund will not invest in companies for the purpose of exercising control or management. 2. The Fund may not invest in the securities of other investment companies, except that it may invest in securities of no-load open-end money market investment companies and investment companies that invest in high yield debt securities if, immediately after any purchase of the securities of any such investment company: (i) securities issued by such investment company and all other investment companies owned by the Fund do not have an aggregate value in excess of 10% of the value of the total assets of the Fund; (ii) the Fund does not own more than three percent of the total outstanding voting stock of such investment company; and (iii) the Fund does not own securities issued by such investment company having an aggregate value in excess of 5% of the value of the total assets of the Fund. The Fund’s investment in securities of other investment companies will be subject to the proportionate share of the management fees and other expenses attributable to such securities of other investment companies. 3. The Fund will not invest in the securities of foreign issuers, except for (i) those securities of the Canadian Government, its provinces and municipalities which are payable in United States currency, and (ii) securities of foreign issuers which are payable in United States dollars (“Yankee Bonds”). The Fund may also invest in Euro-dollar obligations with maturities up to one year, but the Fund will not acquire Yankee Bonds or Euro-dollar obligations if the acquisition would cause more than 15% of the Fund’s assets to be invested in Yankee Bonds and Euro-dollar obligations. 4. The Fund will not invest more than 2% of the value of its total assets in warrants (valued at the lower of cost or market), except warrants acquired on initial issuance where the warrants are attached to or otherwise in a unit with other securities. |
| Risk Factors [Table Text Block] | Note 7 − Principal Risks — Fixed-income market risk. Interest rate risk. a fixed-income security with a duration of three years would be expected to decline 3% if interest rates rose 1%. Conversely, the market price of the same security would be expected to increase 3% if interest rates fell 1%. Asset-Backed Securities Risk Credit risk. Cybersecurity and operational risk. Derivatives risk. Economic, geopolitical and market events risk. As a result of certain geopolitical tensions and armed conflicts outside of the United States, the extent and ultimate result of which are unknown at this time, the United States and the European Union, along with the regulatory bodies of a number of countries, have imposed economic sanctions on certain countries, corporate entities and individuals. The imposition of such sanctions and other similar measures could cause, among other things, a decline in the value and/or liquidity of securities issued, downgrades in the credit ratings of securities and cause increased market volatility affect- ing not only the party but throughout the world. Sanctions could also result in a party taking counter measures or retaliatory actions which may further impair the value and liquidity of some securities. ETF and other investment company risk. Foreign investment risk. Government securities risk. High yield securities risk. Issuer risk. Leverage risk. Liquidity risk. securities may be harder to value or sell at an acceptable price, especially during times of market volatility or decline. Investments in foreign securities tend to have greater exposure to liquidity risk than domestic securities. Management risk. Market risk. The impact of pandemic risks may last for an extended period of time and result in a substantial economic downturn. Any such impact could adversely affect the Fund’s performance. Risk of market price discount from net asset value. Valuation risk. |
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |
| Document Period End Date | Mar. 31, 2024 |
| Principal Risks [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Principal Risks — |
| Fixed-income market risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Fixed-income market risk. |
| Interest rate risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Interest rate risk. a fixed-income security with a duration of three years would be expected to decline 3% if interest rates rose 1%. Conversely, the market price of the same security would be expected to increase 3% if interest rates fell 1%. |
| Asset-Backed Securities Risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Asset-Backed Securities Risk |
| Credit risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Credit risk. |
| Cybersecurity and operational risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Cybersecurity and operational risk. |
| Derivatives risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Derivatives risk. |
| Economic, geopolitical and market events risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Economic, geopolitical and market events risk. As a result of certain geopolitical tensions and armed conflicts outside of the United States, the extent and ultimate result of which are unknown at this time, the United States and the European Union, along with the regulatory bodies of a number of countries, have imposed economic sanctions on certain countries, corporate entities and individuals. The imposition of such sanctions and other similar measures could cause, among other things, a decline in the value and/or liquidity of securities issued, downgrades in the credit ratings of securities and cause increased market volatility affect- ing not only the party but throughout the world. Sanctions could also result in a party taking counter measures or retaliatory actions which may further impair the value and liquidity of some securities. |
| ETF and other investment company risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | ETF and other investment company risk. |
| Foreign investment risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Foreign investment risk. |
| Government securities risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Government securities risk. |
| High yield securities risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | High yield securities risk. |
| Issuer risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Issuer risk. |
| Leverage risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Leverage risk. |
| Liquidity risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Liquidity risk. securities may be harder to value or sell at an acceptable price, especially during times of market volatility or decline. Investments in foreign securities tend to have greater exposure to liquidity risk than domestic securities. |
| Management risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Management risk. |
| Market risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Market risk. The impact of pandemic risks may last for an extended period of time and result in a substantial economic downturn. Any such impact could adversely affect the Fund’s performance. |
| Risk of market price discount from net asset value [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Risk of market price discount from net asset value. |
| Valuation risk [Member] | |
| General Description of Registrant [Abstract] | |
| Risk [Text Block] | Valuation risk. |
