Investor A, C, Institutional and Class R [Member] Investment Risks - Investor A, C, Institutional and Class R [Member] - BLACKROCK HEALTH SCIENCES OPPORTUNITIES PORTFOLIO	May 31, 2025
Healthcare Related Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Healthcare-Related Securities Risk — Healthcare companies are strongly affected by worldwide scientific or technological developments. Their products may rapidly become obsolete. Many healthcare companies are also subject to significant government regulation and may be affected by changes in governmental policies.
Concentration Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Concentration Risk — The Fund’s strategy of concentrating in health sciences and related companies means that its performance will be closely tied to the performance of a particular market segment. The Fund’s concentration in these companies may present more risks than if it were broadly diversified over numerous industries and sectors of the economy. A downturn in these companies would have a larger impact on the Fund than on a mutual fund that does not concentrate in such companies. At times, the performance of these companies will lag the performance of other industries or the broader market as a whole.
Foreign Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include: ◼ The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight. ◼ Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio. ◼ The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position. ◼ The governments of certain countries, or the U.S. Government with respect to certain countries, may prohibit or impose substantial restrictions through capital controls and/or sanctions on foreign investments in the capital markets or certain industries in those countries, which may prohibit or restrict the ability to own or transfer currency, securities, derivatives or other assets. ◼ Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws. ◼ Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments. ◼ The Fund’s claims to recover foreign withholding taxes may not be successful, and if the likelihood of recovery of foreign withholding taxes materially decreases, due to, for example, a change in tax regulation or approach in the foreign country, accruals in the Fund’s net asset value for such refunds may be written down partially or in full, which will adversely affect the Fund’s net asset value.
Geographic Concentration Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Geographic Concentration Risk — From time to time the Fund may invest a substantial amount of its assets in issuers located in a single country or a limited number of countries. If the Fund concentrates its investments in this manner, it assumes the risk that economic, political and social conditions in those countries will have a significant impact on its investment performance. The Fund’s investment performance may also be more volatile if it concentrates its investments in certain countries, especially emerging market countries.
Investment Style Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Investment Style Risk — Under certain market conditions, growth investments have performed better during the later stages of economic expansion. Therefore, this investment style may over time go in and out of favor. At times when the investment style used by the Fund is out of favor, the Fund may underperform other equity funds that use different investment styles.
Market Risk and Selection Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. The value of a security or other asset may decline due to changes in general market conditions, economic trends or events that are not specifically related to the issuer of the security or other asset, or factors that affect a particular issuer or issuers, exchange, country, group of countries, region, market, industry, group of industries, sector or asset class. Local, regional or global events such as war, acts of terrorism, the spread of infectious illness or other public health issues like pandemics or epidemics, recessions, or other events could have a significant impact on the Fund and its investments. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
Mid Cap Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Mid Cap Securities Risk — The securities of mid cap companies generally trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.
Operational and Technology Risks [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Operational and Technology Risks — The Fund is directly and indirectly susceptible to operational and technology risks, including those related to human errors, processing errors, communication errors, systems failures, cybersecurity incidents, and the use of artificial intelligence and machine learning (“AI”), which may result in losses for the Fund and its shareholders or may impair the Fund’s operations. While the Fund’s service providers are required to have appropriate operational, information security and cybersecurity risk management policies and procedures, their methods of risk management may differ from those of the Fund. Operational and technology risks for the issuers in which the Fund invests could also result in material adverse consequences for such issuers and may cause the Fund’s investments in such issuers to lose value.
Risk of Investing in the United States [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Risk of Investing in the United States — Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.
Small Cap Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Small Cap Securities Risk — Small cap companies may have limited product lines or markets. They may be less financially secure than larger, more established companies. They may depend on a more limited management group than larger capitalized companies.
Equity Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	◼ Equity Securities Risk — Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.
Risk Lose Money [Member]
Prospectus [Line Items]
Risk [Text Block]	You may lose part or all of yourinvestment in the Fund or your investment may not perform as well as other similar investments.