S000046220 [Member] Investment Strategy - BATS: High Income Municipal Series	Mar. 31, 2026
Prospectus [Line Items]
Strategy [Heading]	Principal Investment Strategies of the Fund
Strategy Narrative [Text Block]	Under normal circumstances, the Fund seeks to invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in investments the income of which is free from federal income tax and derivatives that provide investment exposure to such securities or to one or more market risk factors associated with such securities. The Fund seeks to provide investors with greater federal tax-free income, in comparison with other municipal bond funds that invest primarily in investment grade securities, by investing in a combination of investment grade and non-investment grade municipal bonds. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for federal income tax purposes (except that the interest may be includable in taxable income for purposes of the federal alternative minimum tax). Issuers of municipal bonds may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include private activity bonds, short-term tax-exempt obligations like municipal notes and variable rate demand obligations. The Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds. Currently, the Fund expects to invest approximately 50% of its net assets in below investment grade municipal bonds. While the level of the Fund’s investments in below investment grade municipal bonds may vary depending on market conditions, the Fund will not invest more than 70% of its net assets, at the time of purchase, in below investment grade municipal bonds, as rated by the independent rating agencies at the time of purchase (BB or lower by S&P Global Ratings (“S&P”) and Fitch Ratings, Inc. (“Fitch”), and Ba or lower by Moody’s Investors Service, Inc. (“Moody’s”)), or if unrated, determined to be of comparable quality by Fund management. Obligations rated BB or lower and Ba or lower are commonly known as “junk bonds.” Split rated bonds will be considered to have the higher credit rating. Split rated bonds are bonds that receive different ratings from two or more rating agencies. The Fund is permitted to engage in transactions in certain derivatives, including, but not limited to, financial futures contracts and options thereon, options, indexed and inverse floating rate obligations and swap agreements, including credit default swap agreements. Derivatives are financial instruments whose value is derived from another security or an index . The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. Derivatives may allow the Fund to increase or decrease its risk exposure more quickly and efficiently than other types of instruments. The Fund is not required to use hedging and may choose not to do so. The Fund intends to invest so that no more than 25% of the Fund’s net assets are represented by the municipal securities of issuers located in the same state. The Fund may also invest up to 10% of its net assets in municipal bonds that are considered “distressed securities.” Distressed securities are securities that are the subject of bankruptcy proceedings or otherwise in default as to the repayment of principal and/or payment of interest at the time of acquisition or are rated in the lowest rating categories by the independent rating agencies (CC or lower by S&P and Fitch, and Ca or lower by Moody’s), or if unrated, determined to be of comparable quality by Fund management. Generally, the Fund will invest in distressed securities when Fund management believes they offer significant potential for higher returns or can be exchanged for other securities that offer this potential. However, there can be no assurance that the Fund will achieve these returns or that the issuer will make an exchange offer or adopt a plan of reorganization.

Under normal circumstances, the Fund seeks to invest at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in investments the income of which is free from federal income tax and derivatives that provide investment exposure to such securities or to one or more market risk factors associated with such securities.

The Fund seeks to provide investors with greater federal tax-free income, in comparison with other municipal bond funds that invest primarily in investment grade securities, by investing in a combination of investment grade and non-investment grade municipal bonds. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for federal income tax purposes (except that the interest may be includable in taxable income for purposes of the federal alternative minimum tax). Issuers of municipal bonds may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include private activity bonds, short-term tax-exempt obligations like municipal notes and variable rate demand obligations.

The Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds. Currently, the Fund expects to invest approximately 50% of its net assets in below investment grade municipal bonds. While the level of the Fund’s investments in below investment grade municipal bonds may vary depending on market conditions, the Fund will not invest more than 70% of its net assets, at the time of purchase, in below investment grade municipal bonds, as rated by the independent rating agencies at the time of purchase (BB or lower by S&P Global Ratings (“S&P”) and Fitch Ratings, Inc. (“Fitch”), and Ba or lower by Moody’s Investors Service, Inc. (“Moody’s”)), or if unrated, determined to be of comparable quality by Fund management. Obligations rated BB or lower and Ba or lower are commonly known as “junk bonds.” Split rated bonds will be considered to have the higher credit rating. Split rated bonds are bonds that receive different ratings from two or more rating agencies.

The Fund is permitted to engage in transactions in certain derivatives, including, but not limited to, financial futures contracts and options thereon, options, indexed and inverse floating rate obligations and swap agreements, including credit default swap agreements. Derivatives are financial instruments whose value is derived from another security or an index . The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. Derivatives may allow the Fund to increase or decrease its risk exposure more quickly and efficiently than other types of instruments. The Fund is not required to use hedging and may choose not to do so.

The Fund may also invest up to 10% of its net assets in municipal bonds that are considered “distressed securities.” Distressed securities are securities that are the subject of bankruptcy proceedings or otherwise in default as to the repayment of principal and/or payment of interest at the time of acquisition or are rated in the lowest rating categories by the independent rating agencies (CC or lower by S&P and Fitch, and Ca or lower by Moody’s), or if unrated, determined to be of comparable quality by Fund management. Generally, the Fund will invest in distressed securities when Fund management believes they offer significant potential for higher returns or can be exchanged for other securities that offer this potential. However, there can be no assurance that the Fund will achieve these returns or that the issuer will make an exchange offer or adopt a plan of reorganization.