| N-2 - USD ($) $ / shares in Units, $ in Thousands | 6 Months Ended | ||||||||||
| Mar. 31, 2024 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021 | Sep. 30, 2020 | Sep. 30, 2019 | Sep. 30, 2018 | |||||
| Cover [Abstract] | |||||||||||
| Entity Central Index Key | 0001635977 | ||||||||||
| Amendment Flag | false | ||||||||||
| Document Type | N-CSRS | ||||||||||
| Entity Registrant Name | abrdn World Healthcare Fund | ||||||||||
| Document Period End Date | Mar. 31, 2024 | ||||||||||
| Financial Highlights [Abstract] | |||||||||||
| Senior Securities Amount | $ 120,000 | [1] | $ 120,000 | [2] | $ 120,000 | $ 120,000 | $ 120,000 | $ 120,000 | |||
| Senior Securities Coverage per Unit | $ 4,992 | [1] | $ 4,726 | [2] | $ 4,786 | $ 5,714 | $ 4,554 | $ 4,396 | |||
| General Description of Registrant [Abstract] | |||||||||||
| Risk Factors [Table Text Block] | 9. Portfolio Investment Risks a. Concentration Risk: The Fund’s portfolio may be more sensitive to, and possibly more adversely affected by, regulatory, economic or political factors or trends relating to the healthcare industries than a portfolio of companies representing a larger number of industries. This risk is in addition to the risks normally associated with any strategy seeking capital appreciation by investing in a portfolio of equity securities. As a result of its concentration policy, the Fund’s investments may be subject to greater risk than a fund that has securities representing a broader range of investments and may cause the value of the Fund’s shares to fluctuate significantly over relatively short periods of time. b. Convertible Securities Risk: Convertible securities generally offer lower interest or dividend yields than nonconvertible debt securities of similar quality. The market value of convertible securities tends to decline as interest rates increase and, conversely, tends to increase as interest rates decline. In addition, because of the conversion feature, the market value of convertible securities tends to vary with fluctuations in the market value of the underlying common stock. Consequently, a unique feature of convertible securities is that as the market price of the underlying common stock declines, convertible securities tend to trade increasingly on a yield basis, and so may not experience market value declines to the same extent as the underlying common stock. Investments in convertible securities generally entail less risk than investments in common stock of the same issuer but more risk than the issuer’s debt obligations. c. Derivatives Risk (including Options, Futures and Swaps): Derivatives are speculative and may hurt the Fund’s performance. The potential benefits to be derived from the Fund’s options, futures and derivatives strategy are dependent upon the portfolio managers’ ability to discern pricing inefficiencies and predict trends in these markets, which decisions could prove to be inaccurate. d. Equity-Linked Notes: The Fund may invest in equity-linked notes, which are generally subject to the same risks as the foreign equity securities or the basket of foreign securities they are linked to. If the linked security(ies) declines in value, the note may return a lower amount at maturity. The trading price of an equity-linked note also depends on the value of the linked security(ies). e. Equity Securities Risk: The stock or other security of a company may not perform as well as expected, and may decrease in value, because of factors related to the company (such as poorer than expected earnings or certain management decisions) or to the industry in which the company is engaged (such as a reduction in the demand for products or services in a particular industry). Holders of common stock generally are subject to more risks than holders of preferred stock or debt securities because the right to repayment of common shareholders' claims is subordinated to that of preferred stock and debt securities upon the bankruptcy of the issuer. f. Foreign Securities Risk: Foreign countries in which the Fund may invest may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of the Fund's investments may decline because of factors such as unfavorable or unsuccessful government actions, reduction of government or central bank support and political or financial instability. To the extent the Fund focuses its investments in a single country or only a few countries in a particular geographic region, economic, political, regulatory or other conditions affecting such country or region may have a greater impact on Fund performance relative to a more geographically diversified fund. g. Key Personnel Risk: There may be only a limited number of securities professionals who have comparable experience to that of the Fund’s existing portfolio management team in the area of healthcare companies. If one or more of the team members dies, resigns, retires or is otherwise unable to act on behalf of the Investment Adviser, there can be no assurance that a suitable replacement could be found immediately. h. Leverage Risk: The Fund may use leverage to purchase securities. Increases and decreases in the value of the Fund's portfolio will be magnified when the Fund uses leverage. i. Market Events Risk: Markets are affected by numerous factors, including interest rates, the outlook for corporate profits, the health of the national and world economies, the fluctuation of other stock markets around the world, and financial, economic and other global market developments and disruptions, such as those arising from war, terrorism, market manipulation, government interventions, trading and tariff arrangements, defaults and shutdowns, political changes or diplomatic developments, public health emergencies and natural/environmental disasters. Such events can negatively impact the securities markets and cause the Fund to lose value. Policy and legislative changes in countries around the world are affecting many aspects of financial regulation, and governmental and quasi-governmental authorities and regulators throughout the world have previously responded to serious economic disruptions with a variety of significant fiscal and monetary policy changes. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time. In addition, economies and financial markets throughout the world are becoming increasingly interconnected. As a result, whether or not the Fund invests in securities of issuers located in or with significant exposure to countries or sectors experiencing economic and financial difficulties, the value and liquidity of the Fund’s investments may be negatively affected by such events. j. REIT and Real Estate Risk: Investment in real estate investment trusts ("REITs") and real estate involves the risks that are associated with direct ownership of real estate and with the real estate industry in general. These risks include: declines in the value of real estate; risks related to local economic conditions, overbuilding and increased competition; increases in property taxes and operating expenses; changes in zoning laws; casualty or condemnation losses; variations in rental income, neighborhood values or the appeal of properties to tenants; changes in interest rates and changes in general economic and market conditions; reduced demand for commercial and office space; increased maintenance or tenant improvement costs to convert properties for other uses; default risk of tenants and borrowers; the financial condition of tenants, buyers and sellers; and the inability to re-lease space on attractive terms or to obtain mortgage financing on a timely basis or at all. REITs’ share prices may decline because of adverse developments affecting the real estate industry including changes in interest rates. The returns from REITs may trail returns from the overall market. Additionally, there is always a risk that a given REIT will fail to qualify for favorable tax treatment. REITs may be leveraged, which increases risk. Certain REITs charge management fees, which may result in layering the management fee paid by the Fund. k. Restricted Securities and Valuation Risk: Some of the Fund’s investments are subject to restrictions on resale and generally have no established trading market or are otherwise illiquid with little or no trading activity. The valuation process requires an analysis of various factors. The Fund’s fair value methodology includes the examination of, among other things, (i) the existence of any contractual restrictions on the disposition of the securities; (ii) information obtained from the issuer which may include an analysis of the company’s financial statements, the company’s products or intended markets, or the company’s technologies; and (iii) the price of a security sold at arm’s length in an issuer’s subsequent completed round of financing. As there is typically no readily available market value for some of the Restricted Securities in the Fund’s portfolio, such Restricted Securities in the Fund’s portfolio are valued at fair value as determined in good faith by or under the direction of the Board pursuant to the Fund’s valuation policy and a consistently applied valuation process. Because of the inherent uncertainty of determining the fair value of investments that do not have a readily available market value, the fair value of the Fund’s investments determined in good faith by the Board may differ significantly from the values that would have been used had a ready market existed for the investments, and the differences could be material. l. Risks Associated with the Fund’s Option Strategy: The ability of the Fund to achieve its investment objective is partially dependent on the successful implementation of its option strategy. There are several risks associated with transactions in options on securities used in connection with the Fund's option strategy. For example, there are significant differences between the securities and options markets that could result in an imperfect correlation between these markets, causing a given transaction not to achieve its objectives. A decision as to whether, when and how to use options involves the exercise of skill and judgment, and even a well-conceived transaction may be unsuccessful to some degree because of market behavior or unexpected events. As the writer of a call option covered with a security held by the Fund, the Fund forgoes, during the option's life, the opportunities to profit from increases in the market value of the security covering the call option above the sum of the premium and the strike price of the call but retains the risk of loss should the price of the underlying security decline. As the Fund writes such covered calls over more of its portfolio, its ability to benefit from capital appreciation becomes more limited. To the extent the Fund writes call options that are not fully covered by securities in its portfolio (such as calls on an index or sector), it will lose money if the portion of the security or securities underlying the option that is not covered by securities in the Fund's portfolio appreciate in value above the exercise price of the option by an amount that exceeds the premium received on the option plus the exercise price of the option. The amount of this loss theoretically could be unlimited. The writer of an option has no control over the time when it may be required to fulfill its obligations as a writer of the option. When the Fund writes put options, it bears the risk of loss if the value of the underlying stock declines below the exercise price minus the put premium. If the option is exercised, the Fund could incur a loss if it is required to purchase the stock underlying the put option at a price greater than the market price of the stock at the time of exercise plus the put premium the Fund received when it wrote the option. While the Fund's potential gain as the writer of a covered put option is limited to the premium received from the purchaser of the put option, the Fund risks a loss equal to the entire exercise price of the option minus the put premium. m. Sector Risk: To the extent that the Fund has a significant portion of its assets invested in securities conducting business in a broadly related group of industries within an economic sector, the Fund may be more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly. Pharmaceutical Sector Risk . The success of companies in the pharmaceutical sector is highly dependent on the development, procurement and marketing of drugs. The values of pharmaceutical companies are also dependent on the development, protection and exploitation of intellectual property rights and other proprietary information, and the profitability of pharmaceutical companies may be significantly affected by such things as the expiration of patents or the loss of, or the inability to enforce, intellectual property rights. The research and other costs associated with developing or procuring new drugs and the related intellectual property rights can be significant, and the results of such research and expenditures are unpredictable. There can be no assurance that those efforts or costs will result in the development of a profitable drug. The pharmaceutical sector is also subject to rapid and significant technological change and competitive forces that may make drugs obsolete or make it difficult to raise prices and, in fact, may result in price discounting. Companies in the pharmaceutical sector may also be subject to expenses and losses from extensive litigation based on intellectual property, product liability and similar claims. Companies in the pharmaceutical sector may be adversely affected by government regulation and changes in reimbursement rates. The ability of many pharmaceutical companies to commercialize and monetize current and any future products depends in part on the extent to which reimbursement for the cost of such products and related treatments are available from third-party payors, such as Medicare, Medicaid, private health insurance plans and health maintenance organizations. Biotechnology Industry Risk. The success of biotechnology companies is highly dependent on the development, procurement and/or marketing of drugs. The values of biotechnology companies are also dependent on the development, protection and exploitation of intellectual property rights and other proprietary information, and the profitability of biotechnology companies may be significantly affected by such things as the expiration of patents or the loss of, or the inability to enforce, intellectual property rights The research and other costs associated with developing or procuring new drugs, products or technologies and the related intellectual property rights can be significant, and the results of such research and expenditures are unpredictable. There can be no assurance that those efforts or costs will result in the development of a profitable drug, product or technology. The biotechnology sector is also subject to rapid and significant technological change and competitive forces that may make drugs, products or technologies obsolete or make it difficult to raise prices and, in fact, may result in price discounting. Companies in the biotechnology sector may also be subject to expenses and losses from extensive litigation based on intellectual property, product liability and similar claims. Companies in the biotechnology sector may be adversely affected by government regulation and changes in reimbursement rates. Healthcare providers, principally hospitals, that transact with companies in the biotechnology industry, often rely on third party payors, such as Medicare, Medicaid, private health insurance plans and health maintenance organizations to reimburse all or a portion of the cost of healthcare related products or services. Biotechnology companies will continue to be affected by the efforts of governments and third-party payors to contain or reduce health care costs. Managed Care Sector Risk. Companies in the managed care sector often assume the risk of both medical and administrative costs for their customers in return for monthly premiums. The profitability of these products depends in large part on the ability of such companies to predict, price for, and effectively manage medical costs. Managed care companies base the premiums they charge and their Medicare bids on estimates of future medical costs over the fixed contract period; however, many factors may cause actual costs to exceed what was estimated and reflected in premiums or bids. Managed care companies are regulated at the federal, state, local and international levels. The evolution of the ACA and other regulatory reforms could materially and adversely affect the manner in which U.S. managed care companies conduct business and their results of operations, financial position and cash flows. New laws or regulations could drive substantial change to the way healthcare products and services are currently delivered and paid for in the United States. A transformative overhaul of the U.S. healthcare system could impact the financial viability of managed care companies in which the Fund may invest. Life Science and Tools Industry Risk. Life science industries are characterized by limited product focus, rapidly changing technology, extensive government regulation, and intense competition. In particular, technological advances can render an existing product, which may account for a disproportionate share of a company’s revenue, obsolete. Extensive regulation can delay cause delays in product development, which may disadvantage a company in an intensely competitive environment. These various factors may result in abrupt advances and declines in the securities prices of particular companies, and, in some cases, may have a broad effect on the prices of securities of companies in particular life science industries. Healthcare Technology Sector Risk. Companies in the healthcare technology sector may incur substantial cost related to product-related liabilities, interruptions at their data centers or client support facilities, claims for infringement or misappropriation of intellectual property rights of others, or infringement or misappropriation of their intellectual property. Each of these may adversely impact the prices of securities of companies in the healthcare technology sector. Additionally, the success of healthcare technology companies depends upon the recruitment and retention of key personnel. The failure to attract and retain qualified personnel could have a material adverse effect on healthcare technology companies’ prospects for long-term growth. Healthcare Services Sector Risk. The operations of healthcare services companies are subject to extensive federal, state and local government regulations. A violation or departure from any of these legal requirements may result in government audits, lower reimbursements, significant fines and penalties, the potential loss of certification, recoupment efforts or voluntary repayments. If healthcare services companies fail to adhere to all of the complex government regulations that apply to their businesses, such companies could suffer severe consequences that would substantially reduce revenues, earnings, cash flows and stock prices. A substantial percentage of a healthcare services company’s service revenues may be generated from patients who have state Medicaid or other non-Medicare government-based programs, such as coverage through the Department of Veterans Affairs (“VA”), as their primary coverage. As state governments and other governmental organizations face increasing budgetary pressure, healthcare services companies may in turn face reductions in payment rates, delays in the receipt of payments, limitations on enrollee eligibility or other changes to the applicable programs. Healthcare Supplies Sector Risk. If healthcare supplies companies are unable to successfully expand their product lines through internal research and development and acquisitions or are unable to successfully grow their business through marketing partnerships, their business may be materially and adversely affected. Quality is extremely important to healthcare supplies companies and their customers due to the serious and costly consequences of product failure. Quality certifications are critical to the marketing success of their products and services. If a healthcare supplies company fails to meet these standards or fails to adapt to evolving standards, its reputation could be damaged, it could lose customers, and its revenue and results of operations could decline. Healthcare Facilities Sector Risk. A healthcare facility’s ability to negotiate favorable contracts significantly affects the revenues and operating results of such healthcare facilities. If a healthcare facility is unable to enter into and maintain managed care contractual arrangements on acceptable terms, if it experiences material reductions in the contracted rates received from managed care payers, or if it has difficulty collecting from managed care payers, its results of operations could be adversely affected. Further changes in the Medicare and Medicaid programs or other government health care programs could have an adverse effect on a healthcare facility’s business. In addition to the changes affected by the ACA, the Medicare and Medicaid programs are subject to other regulatory changes which could materially increase or decrease payments from government programs in the future, as well as affect the cost of providing services to patients and the timing of payments to facilities, which could in turn adversely affect a healthcare facility’s overall business, financial condition, results of operations or cashflows. Healthcare Equipment Sector Risk. The medical device markets are highly competitive and characterized by rapid change, which may affect a company’s ability to be competitive. They are also rigorously regulated and it is anticipated that governmental authorities will continue to scrutinize this industry closely, and that additional regulation may increase compliance and legal costs, exposure to litigation, and other adverse effects to operations. Healthcare equipment companies are substantially dependent on patent and other proprietary rights and failing to protect such rights or to be successful in litigation related to such rights may negatively impact the ability of healthcare equipment companies to sell current or future products. Quality problems with the processes, goods and services of a healthcare equipment company could harm the company’s reputation for producing high-quality products and erode its competitive advantage, sales and market share. Quality certifications are critical to the marketing success of goods and services. If a healthcare equipment company fails to meet these standards, its reputation could be damaged, it could lose customers, and its revenue and results of operations could decline. Healthcare Distributors Sector Risk. Companies in the healthcare distribution sector operate in markets that are highly competitive and in an industry that is highly regulated and often subject to legal proceedings. Due to the nature of the business of healthcare distribution companies, each of the above may have an adverse impact on the securities prices of companies in the healthcare distribution sector. Healthcare distribution companies depend on the availability of various components, compounds, raw materials and energy supplied by others for their operations. Any of these supplier relationships could be interrupted due to events beyond the control of such companies, including pandemics, epidemics or natural disasters, or could be terminated. A sustained supply interruption could have an adverse effect on business. n. Valuation Risk: The price that the Fund could receive upon the sale of any particular portfolio investment may differ from the Fund's valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair valuation methodology or a price provided by an independent pricing service. As a result, the price received upon the sale of an investment may be less than the value ascribed by the Fund, and the Fund could realize a greater than expected loss or lower than expected gain upon the sale of the investment. The Fund's ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third-party service providers. o. Venture Capital Investments Risk: The Fund may occasionally invest in venture capital opportunities. While these securities offer the opportunity for significant capital gains, such investments also involve a degree of risk that can result in substantial losses. Some of the venture capital opportunities in which the Fund may invest are expected to be companies that are in a “start-up” stage of development, have little or no operating history, operate at a loss or with substantial variations in operating results from period to period, have limited products, markets, financial resources or management depth, or have the need for substantial additional “follow-on” capital to support expansion or to achieve or maintain a competitive position. Such additional investments may dilute the interests of prior investors, such as the Fund. Some of these companies may be emerging companies at the research and development stage with no marketable or approved products or technology. There can be no assurance that securities of start-up or emerging growth companies will, in the future, yield returns commensurate with their associated risks. These investments, which are considered Restricted Securities, will be made primarily in convertible preferred stock. The Fund may also purchase non-convertible debt securities in connection with its venture capital investments, and otherwise when the Investment Adviser believes that such investments would be consistent with the Fund’s investment objective. While these debt investments typically will not be rated, the Investment Adviser believes that, in light of the risk characteristics associated with investments in emerging growth companies, if such investments were to be compared with investments rated by S&P or Moody’s, they may be rated as low as “C” in the rating categories established by S&P and Moody’s. Such securities are commonly referred to as “junk bonds” and are considered, on balance, as predominantly speculative. | ||||||||||
| Lowest Price or Bid | $ 9.84 | ||||||||||
| Highest Price or Bid | 13.23 | ||||||||||
| Lowest Price or Bid, NAV | 10.88 | ||||||||||
| Highest Price or Bid, NAV | $ 12.53 | ||||||||||
| Highest Price or Bid, Premium (Discount) to NAV [Percent] | 7.78% | ||||||||||
| Lowest Price or Bid, Premium (Discount) to NAV [Percent] | (9.56%) | ||||||||||
| Share Price | [3] | $ 13.23 | [1] | 11.72 | [2] | 12.86 | 16.45 | 14.33 | 13.44 | ||
| NAV Per Share | [3] | $ 12.53 | [1] | $ 11.73 | [1],[2] | $ 12.11 | [2] | $ 15.18 | $ 14.14 | $ 13.51 | $ 15.24 |
| Latest Premium (Discount) to NAV [Percent] | 5.59% | (0.09%) | |||||||||
| Capital Stock, Long-Term Debt, and Other Securities [Abstract] | |||||||||||
| Outstanding Security, Held [Shares] | 38,244,601 | ||||||||||
| Concentration Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | a. Concentration Risk: The Fund’s portfolio may be more sensitive to, and possibly more adversely affected by, regulatory, economic or political factors or trends relating to the healthcare industries than a portfolio of companies representing a larger number of industries. This risk is in addition to the risks normally associated with any strategy seeking capital appreciation by investing in a portfolio of equity securities. As a result of its concentration policy, the Fund’s investments may be subject to greater risk than a fund that has securities representing a broader range of investments and may cause the value of the Fund’s shares to fluctuate significantly over relatively short periods of time. | ||||||||||
| Convertible Securities Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | b. Convertible Securities Risk: Convertible securities generally offer lower interest or dividend yields than nonconvertible debt securities of similar quality. The market value of convertible securities tends to decline as interest rates increase and, conversely, tends to increase as interest rates decline. In addition, because of the conversion feature, the market value of convertible securities tends to vary with fluctuations in the market value of the underlying common stock. Consequently, a unique feature of convertible securities is that as the market price of the underlying common stock declines, convertible securities tend to trade increasingly on a yield basis, and so may not experience market value declines to the same extent as the underlying common stock. Investments in convertible securities generally entail less risk than investments in common stock of the same issuer but more risk than the issuer’s debt obligations. | ||||||||||
| Derivatives Risk Including Options, Futures And Swaps [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | c. Derivatives Risk (including Options, Futures and Swaps): Derivatives are speculative and may hurt the Fund’s performance. The potential benefits to be derived from the Fund’s options, futures and derivatives strategy are dependent upon the portfolio managers’ ability to discern pricing inefficiencies and predict trends in these markets, which decisions could prove to be inaccurate. | ||||||||||
| Equity Linked Notes Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | d. Equity-Linked Notes: The Fund may invest in equity-linked notes, which are generally subject to the same risks as the foreign equity securities or the basket of foreign securities they are linked to. If the linked security(ies) declines in value, the note may return a lower amount at maturity. The trading price of an equity-linked note also depends on the value of the linked security(ies). | ||||||||||
| Equity Securities Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | e. Equity Securities Risk: The stock or other security of a company may not perform as well as expected, and may decrease in value, because of factors related to the company (such as poorer than expected earnings or certain management decisions) or to the industry in which the company is engaged (such as a reduction in the demand for products or services in a particular industry). Holders of common stock generally are subject to more risks than holders of preferred stock or debt securities because the right to repayment of common shareholders' claims is subordinated to that of preferred stock and debt securities upon the bankruptcy of the issuer. | ||||||||||
| Foreign Securities Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | f. Foreign Securities Risk: Foreign countries in which the Fund may invest may have markets that are less liquid, less regulated and more volatile than U.S. markets. The value of the Fund's investments may decline because of factors such as unfavorable or unsuccessful government actions, reduction of government or central bank support and political or financial instability. To the extent the Fund focuses its investments in a single country or only a few countries in a particular geographic region, economic, political, regulatory or other conditions affecting such country or region may have a greater impact on Fund performance relative to a more geographically diversified fund. | ||||||||||
| Key Personnel Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | g. Key Personnel Risk: There may be only a limited number of securities professionals who have comparable experience to that of the Fund’s existing portfolio management team in the area of healthcare companies. If one or more of the team members dies, resigns, retires or is otherwise unable to act on behalf of the Investment Adviser, there can be no assurance that a suitable replacement could be found immediately. | ||||||||||
| Leverage Risks [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | h. Leverage Risk: The Fund may use leverage to purchase securities. Increases and decreases in the value of the Fund's portfolio will be magnified when the Fund uses leverage. | ||||||||||
| Market Events Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | i. Market Events Risk: Markets are affected by numerous factors, including interest rates, the outlook for corporate profits, the health of the national and world economies, the fluctuation of other stock markets around the world, and financial, economic and other global market developments and disruptions, such as those arising from war, terrorism, market manipulation, government interventions, trading and tariff arrangements, defaults and shutdowns, political changes or diplomatic developments, public health emergencies and natural/environmental disasters. Such events can negatively impact the securities markets and cause the Fund to lose value. Policy and legislative changes in countries around the world are affecting many aspects of financial regulation, and governmental and quasi-governmental authorities and regulators throughout the world have previously responded to serious economic disruptions with a variety of significant fiscal and monetary policy changes. The impact of these changes on the markets, and the practical implications for market participants, may not be fully known for some time. In addition, economies and financial markets throughout the world are becoming increasingly interconnected. As a result, whether or not the Fund invests in securities of issuers located in or with significant exposure to countries or sectors experiencing economic and financial difficulties, the value and liquidity of the Fund’s investments may be negatively affected by such events. | ||||||||||
| Real Estate Investment Trusts And Real Estate Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | j. REIT and Real Estate Risk: Investment in real estate investment trusts ("REITs") and real estate involves the risks that are associated with direct ownership of real estate and with the real estate industry in general. These risks include: declines in the value of real estate; risks related to local economic conditions, overbuilding and increased competition; increases in property taxes and operating expenses; changes in zoning laws; casualty or condemnation losses; variations in rental income, neighborhood values or the appeal of properties to tenants; changes in interest rates and changes in general economic and market conditions; reduced demand for commercial and office space; increased maintenance or tenant improvement costs to convert properties for other uses; default risk of tenants and borrowers; the financial condition of tenants, buyers and sellers; and the inability to re-lease space on attractive terms or to obtain mortgage financing on a timely basis or at all. REITs’ share prices may decline because of adverse developments affecting the real estate industry including changes in interest rates. The returns from REITs may trail returns from the overall market. Additionally, there is always a risk that a given REIT will fail to qualify for favorable tax treatment. REITs may be leveraged, which increases risk. Certain REITs charge management fees, which may result in layering the management fee paid by the Fund. | ||||||||||
| Restricted Securities And Valuation Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | k. Restricted Securities and Valuation Risk: Some of the Fund’s investments are subject to restrictions on resale and generally have no established trading market or are otherwise illiquid with little or no trading activity. The valuation process requires an analysis of various factors. The Fund’s fair value methodology includes the examination of, among other things, (i) the existence of any contractual restrictions on the disposition of the securities; (ii) information obtained from the issuer which may include an analysis of the company’s financial statements, the company’s products or intended markets, or the company’s technologies; and (iii) the price of a security sold at arm’s length in an issuer’s subsequent completed round of financing. As there is typically no readily available market value for some of the Restricted Securities in the Fund’s portfolio, such Restricted Securities in the Fund’s portfolio are valued at fair value as determined in good faith by or under the direction of the Board pursuant to the Fund’s valuation policy and a consistently applied valuation process. Because of the inherent uncertainty of determining the fair value of investments that do not have a readily available market value, the fair value of the Fund’s investments determined in good faith by the Board may differ significantly from the values that would have been used had a ready market existed for the investments, and the differences could be material. | ||||||||||
| Risks Associated With Funds Option Strategy [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | l. Risks Associated with the Fund’s Option Strategy: The ability of the Fund to achieve its investment objective is partially dependent on the successful implementation of its option strategy. There are several risks associated with transactions in options on securities used in connection with the Fund's option strategy. For example, there are significant differences between the securities and options markets that could result in an imperfect correlation between these markets, causing a given transaction not to achieve its objectives. A decision as to whether, when and how to use options involves the exercise of skill and judgment, and even a well-conceived transaction may be unsuccessful to some degree because of market behavior or unexpected events. As the writer of a call option covered with a security held by the Fund, the Fund forgoes, during the option's life, the opportunities to profit from increases in the market value of the security covering the call option above the sum of the premium and the strike price of the call but retains the risk of loss should the price of the underlying security decline. As the Fund writes such covered calls over more of its portfolio, its ability to benefit from capital appreciation becomes more limited. To the extent the Fund writes call options that are not fully covered by securities in its portfolio (such as calls on an index or sector), it will lose money if the portion of the security or securities underlying the option that is not covered by securities in the Fund's portfolio appreciate in value above the exercise price of the option by an amount that exceeds the premium received on the option plus the exercise price of the option. The amount of this loss theoretically could be unlimited. The writer of an option has no control over the time when it may be required to fulfill its obligations as a writer of the option. When the Fund writes put options, it bears the risk of loss if the value of the underlying stock declines below the exercise price minus the put premium. If the option is exercised, the Fund could incur a loss if it is required to purchase the stock underlying the put option at a price greater than the market price of the stock at the time of exercise plus the put premium the Fund received when it wrote the option. While the Fund's potential gain as the writer of a covered put option is limited to the premium received from the purchaser of the put option, the Fund risks a loss equal to the entire exercise price of the option minus the put premium. | ||||||||||
| Sector Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | m. Sector Risk: To the extent that the Fund has a significant portion of its assets invested in securities conducting business in a broadly related group of industries within an economic sector, the Fund may be more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly. Pharmaceutical Sector Risk . The success of companies in the pharmaceutical sector is highly dependent on the development, procurement and marketing of drugs. The values of pharmaceutical companies are also dependent on the development, protection and exploitation of intellectual property rights and other proprietary information, and the profitability of pharmaceutical companies may be significantly affected by such things as the expiration of patents or the loss of, or the inability to enforce, intellectual property rights. The research and other costs associated with developing or procuring new drugs and the related intellectual property rights can be significant, and the results of such research and expenditures are unpredictable. There can be no assurance that those efforts or costs will result in the development of a profitable drug. The pharmaceutical sector is also subject to rapid and significant technological change and competitive forces that may make drugs obsolete or make it difficult to raise prices and, in fact, may result in price discounting. Companies in the pharmaceutical sector may also be subject to expenses and losses from extensive litigation based on intellectual property, product liability and similar claims. Companies in the pharmaceutical sector may be adversely affected by government regulation and changes in reimbursement rates. The ability of many pharmaceutical companies to commercialize and monetize current and any future products depends in part on the extent to which reimbursement for the cost of such products and related treatments are available from third-party payors, such as Medicare, Medicaid, private health insurance plans and health maintenance organizations. Biotechnology Industry Risk. The success of biotechnology companies is highly dependent on the development, procurement and/or marketing of drugs. The values of biotechnology companies are also dependent on the development, protection and exploitation of intellectual property rights and other proprietary information, and the profitability of biotechnology companies may be significantly affected by such things as the expiration of patents or the loss of, or the inability to enforce, intellectual property rights The research and other costs associated with developing or procuring new drugs, products or technologies and the related intellectual property rights can be significant, and the results of such research and expenditures are unpredictable. There can be no assurance that those efforts or costs will result in the development of a profitable drug, product or technology. The biotechnology sector is also subject to rapid and significant technological change and competitive forces that may make drugs, products or technologies obsolete or make it difficult to raise prices and, in fact, may result in price discounting. Companies in the biotechnology sector may also be subject to expenses and losses from extensive litigation based on intellectual property, product liability and similar claims. Companies in the biotechnology sector may be adversely affected by government regulation and changes in reimbursement rates. Healthcare providers, principally hospitals, that transact with companies in the biotechnology industry, often rely on third party payors, such as Medicare, Medicaid, private health insurance plans and health maintenance organizations to reimburse all or a portion of the cost of healthcare related products or services. Biotechnology companies will continue to be affected by the efforts of governments and third-party payors to contain or reduce health care costs. Managed Care Sector Risk. Companies in the managed care sector often assume the risk of both medical and administrative costs for their customers in return for monthly premiums. The profitability of these products depends in large part on the ability of such companies to predict, price for, and effectively manage medical costs. Managed care companies base the premiums they charge and their Medicare bids on estimates of future medical costs over the fixed contract period; however, many factors may cause actual costs to exceed what was estimated and reflected in premiums or bids. Managed care companies are regulated at the federal, state, local and international levels. The evolution of the ACA and other regulatory reforms could materially and adversely affect the manner in which U.S. managed care companies conduct business and their results of operations, financial position and cash flows. New laws or regulations could drive substantial change to the way healthcare products and services are currently delivered and paid for in the United States. A transformative overhaul of the U.S. healthcare system could impact the financial viability of managed care companies in which the Fund may invest. Life Science and Tools Industry Risk. Life science industries are characterized by limited product focus, rapidly changing technology, extensive government regulation, and intense competition. In particular, technological advances can render an existing product, which may account for a disproportionate share of a company’s revenue, obsolete. Extensive regulation can delay cause delays in product development, which may disadvantage a company in an intensely competitive environment. These various factors may result in abrupt advances and declines in the securities prices of particular companies, and, in some cases, may have a broad effect on the prices of securities of companies in particular life science industries. Healthcare Technology Sector Risk. Companies in the healthcare technology sector may incur substantial cost related to product-related liabilities, interruptions at their data centers or client support facilities, claims for infringement or misappropriation of intellectual property rights of others, or infringement or misappropriation of their intellectual property. Each of these may adversely impact the prices of securities of companies in the healthcare technology sector. Additionally, the success of healthcare technology companies depends upon the recruitment and retention of key personnel. The failure to attract and retain qualified personnel could have a material adverse effect on healthcare technology companies’ prospects for long-term growth. Healthcare Services Sector Risk. The operations of healthcare services companies are subject to extensive federal, state and local government regulations. A violation or departure from any of these legal requirements may result in government audits, lower reimbursements, significant fines and penalties, the potential loss of certification, recoupment efforts or voluntary repayments. If healthcare services companies fail to adhere to all of the complex government regulations that apply to their businesses, such companies could suffer severe consequences that would substantially reduce revenues, earnings, cash flows and stock prices. A substantial percentage of a healthcare services company’s service revenues may be generated from patients who have state Medicaid or other non-Medicare government-based programs, such as coverage through the Department of Veterans Affairs (“VA”), as their primary coverage. As state governments and other governmental organizations face increasing budgetary pressure, healthcare services companies may in turn face reductions in payment rates, delays in the receipt of payments, limitations on enrollee eligibility or other changes to the applicable programs. Healthcare Supplies Sector Risk. If healthcare supplies companies are unable to successfully expand their product lines through internal research and development and acquisitions or are unable to successfully grow their business through marketing partnerships, their business may be materially and adversely affected. Quality is extremely important to healthcare supplies companies and their customers due to the serious and costly consequences of product failure. Quality certifications are critical to the marketing success of their products and services. If a healthcare supplies company fails to meet these standards or fails to adapt to evolving standards, its reputation could be damaged, it could lose customers, and its revenue and results of operations could decline. Healthcare Facilities Sector Risk. A healthcare facility’s ability to negotiate favorable contracts significantly affects the revenues and operating results of such healthcare facilities. If a healthcare facility is unable to enter into and maintain managed care contractual arrangements on acceptable terms, if it experiences material reductions in the contracted rates received from managed care payers, or if it has difficulty collecting from managed care payers, its results of operations could be adversely affected. Further changes in the Medicare and Medicaid programs or other government health care programs could have an adverse effect on a healthcare facility’s business. In addition to the changes affected by the ACA, the Medicare and Medicaid programs are subject to other regulatory changes which could materially increase or decrease payments from government programs in the future, as well as affect the cost of providing services to patients and the timing of payments to facilities, which could in turn adversely affect a healthcare facility’s overall business, financial condition, results of operations or cashflows. Healthcare Equipment Sector Risk. The medical device markets are highly competitive and characterized by rapid change, which may affect a company’s ability to be competitive. They are also rigorously regulated and it is anticipated that governmental authorities will continue to scrutinize this industry closely, and that additional regulation may increase compliance and legal costs, exposure to litigation, and other adverse effects to operations. Healthcare equipment companies are substantially dependent on patent and other proprietary rights and failing to protect such rights or to be successful in litigation related to such rights may negatively impact the ability of healthcare equipment companies to sell current or future products. Quality problems with the processes, goods and services of a healthcare equipment company could harm the company’s reputation for producing high-quality products and erode its competitive advantage, sales and market share. Quality certifications are critical to the marketing success of goods and services. If a healthcare equipment company fails to meet these standards, its reputation could be damaged, it could lose customers, and its revenue and results of operations could decline. Healthcare Distributors Sector Risk. Companies in the healthcare distribution sector operate in markets that are highly competitive and in an industry that is highly regulated and often subject to legal proceedings. Due to the nature of the business of healthcare distribution companies, each of the above may have an adverse impact on the securities prices of companies in the healthcare distribution sector. Healthcare distribution companies depend on the availability of various components, compounds, raw materials and energy supplied by others for their operations. Any of these supplier relationships could be interrupted due to events beyond the control of such companies, including pandemics, epidemics or natural disasters, or could be terminated. A sustained supply interruption could have an adverse effect on business. | ||||||||||
| Valuation Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | n. Valuation Risk: The price that the Fund could receive upon the sale of any particular portfolio investment may differ from the Fund's valuation of the investment, particularly for securities that trade in thin or volatile markets or that are valued using a fair valuation methodology or a price provided by an independent pricing service. As a result, the price received upon the sale of an investment may be less than the value ascribed by the Fund, and the Fund could realize a greater than expected loss or lower than expected gain upon the sale of the investment. The Fund's ability to value its investments may also be impacted by technological issues and/or errors by pricing services or other third-party service providers. | ||||||||||
| Venture Capital Investments Risk [Member] | |||||||||||
| General Description of Registrant [Abstract] | |||||||||||
| Risk [Text Block] | o. Venture Capital Investments Risk: The Fund may occasionally invest in venture capital opportunities. While these securities offer the opportunity for significant capital gains, such investments also involve a degree of risk that can result in substantial losses. Some of the venture capital opportunities in which the Fund may invest are expected to be companies that are in a “start-up” stage of development, have little or no operating history, operate at a loss or with substantial variations in operating results from period to period, have limited products, markets, financial resources or management depth, or have the need for substantial additional “follow-on” capital to support expansion or to achieve or maintain a competitive position. Such additional investments may dilute the interests of prior investors, such as the Fund. Some of these companies may be emerging companies at the research and development stage with no marketable or approved products or technology. There can be no assurance that securities of start-up or emerging growth companies will, in the future, yield returns commensurate with their associated risks. These investments, which are considered Restricted Securities, will be made primarily in convertible preferred stock. The Fund may also purchase non-convertible debt securities in connection with its venture capital investments, and otherwise when the Investment Adviser believes that such investments would be consistent with the Fund’s investment objective. While these debt investments typically will not be rated, the Investment Adviser believes that, in light of the risk characteristics associated with investments in emerging growth companies, if such investments were to be compared with investments rated by S&P or Moody’s, they may be rated as low as “C” in the rating categories established by S&P and Moody’s. Such securities are commonly referred to as “junk bonds” and are considered, on balance, as predominantly speculative. | ||||||||||
| [1]Effective October 27, 2023, abrdn Inc. became the investment adviser of the Fund. Prior to October 27, 2023, the Fund was managed by Tekla Capital Management, LLC.[2]Beginning with the year ended September 30, 2023, the Fund’s financial statements were audited by KPMG LLP. Previous years were audited by a different independent registered public accounting firm.[3]Based on average shares outstanding. | |||||||||||
