v3.26.3
S000039195 [Member] Investment Risks - AB Select US Long/Short Portfolio
Jun. 30, 2026
Short Sale Risk [Member]  
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Short Sale Risk: Short sales involve the risk that the Fund will incur a loss by subsequently buying a security at a higher price than the price at which it sold the security. The amount of such loss is theoretically unlimited, as it will be based on the increase in value of the security sold short. In contrast, the risk of loss from a long position is limited to the Fund’s investment in the security, because the price of the security cannot fall below zero. The Fund may not always be able to close out a short position on favorable terms.
Derivatives Risks [Member]  
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Derivatives Risk: Derivatives may be difficult to price or unwind and leveraged so that small changes may produce disproportionate losses for the Fund. A short position in a derivative instrument involves the risk of a theoretically unlimited increase in the value of the underlying asset, reference rate or index, which could cause the Fund to suffer a potentially unlimited loss. Derivatives, especially over‑the‑counter derivatives, are also subject to counterparty risk, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable or unwilling to honor its contractual obligations to the Fund.
Leverage Risk [Member]  
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Leverage Risk: To the extent the Fund uses leveraging techniques, the value of its shares may be more volatile because leverage tends to exaggerate the effect of any increase or decrease in the value of the Fund’s investments.
Capitalization Risk [Member]  
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Capitalization Risk: Investments in small- and mid‑capitalization companies may be more volatile than investments in large-capitalization companies. Investments in these companies may have additional risks because these companies may have limited product lines, markets or financial resources.
Active Trading Risk [Member]  
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Active Trading Risk: The Fund expects to engage in active and frequent trading of its portfolio securities and its portfolio turnover rate is expected to greatly exceed 100%. A higher rate of portfolio turnover increases transaction costs, which may negatively affect the Fund’s return. In addition, a high rate of portfolio turnover may result in substantial short-term gains, which may have adverse tax consequences for Fund shareholders.
IPO Risk [Member]  
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IPO Risk: Securities purchased in an IPO may be subject to substantial price volatility due to one or more factors such as unseasoned trading in the securities, the lack of investor knowledge of the issuer, the lack of an operating history of the issuer, and the dependence of the issuer on key personnel, suppliers or a limited number of customers.
Management Risk [Member]  
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Management Risk: The Fund is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions for the Fund, but there is no guarantee that its techniques will produce the intended results. Some of these techniques may incorporate, or rely upon, quantitative models, but there is no guarantee that these models will generate accurate forecasts, reduce risk or otherwise perform as expected.
Market Risks [Member]  
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Market Risk: The value of the Fund’s assets will fluctuate as the market or markets in which the Fund invests fluctuate. The value of the Fund’s investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other local, regional or global events, including public health crises (including the occurrence of a contagious disease or illness), terrorism, war, changing interest rate levels, the imposition of new or additional tariffs, or global conflicts, any of which can affect large portions of the securities markets. It includes the risk that a particular style of investing may be underperforming the market generally.
Risk Lose Money [Member]  
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As with all investments, you may lose money by investing in the Fund.