Transamerica High Yield Muni Investment Strategy - Retail Class [Member] - Transamerica High Yield Muni	Oct. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:bold;margin-left:0%;">Principal Investment Strategies:</span>
Strategy Narrative [Text Block]	Under normal circumstances, the fund’s sub-adviser, Belle Haven Investments, L.P. (the “sub-adviser”), invests at least 80% of the fund’s net assets (plus the amount of borrowings, if any, for investment purposes) in municipal fixed-income securities the interest from which is exempt from federal income tax and the federal alternative minimum tax (“AMT”) applicable to individuals. Interest income from some of the municipal obligations in which the fund may invest may be subject to the AMT. The fund primarily invests in “high yield” municipal bonds under normal market conditions. For this purpose, “high yield” municipal bonds are those rated medium to lower grade. The fund normally invests primarily in general obligation and revenue bonds issued by U.S. municipal issuers, as well as issuers in U.S. territories and possessions. The fund may invest 25% or more of its total net assets in any sector or sub-sector of the municipal bond market. The fund pursues an actively managed, total return strategy that seeks to identify inefficiencies in the municipal bond market. The sub-adviser’s investment process is engineered to seek to exploit mispricing that the sub-adviser aims to identify at the issuer, credit, industry, security and/or maturity level based on macro-economic and fundamental analysis. Analysis is also used to determine the fund’s yield curve positioning. Investment decisions are made by the sub-adviser in an effort to maximize total return while balancing portfolio risk. Medium grade municipal bonds are those rated “A” to “BBB” by Standard & Poor’s Rating Services (“S&P”). Lower-grade municipal bonds (commonly known as “junk bonds”) are those rated below “Baa” by Moody’s Investors Service, Inc. (“Moody’s”) or lower than “BBB” by S&P or Fitch, Inc. (“Fitch”) or comparable ratings by other nationally recognized rating organizations (or, in the case of unrated securities, determined by the sub-adviser to be of comparable quality). The fund has the flexibility to invest the remainder of its assets in a broad array of issuers across the credit spectrum. The fund may also invest up to 15% of its net assets in municipal bonds that are distressed securities. Distressed securities are securities that are the subject of bankruptcy proceedings or are rated in the lowest rating categories by at least one independent rating agency (“CC” or lower by S&P or Fitch or “Ca” or lower by Moody’s), or if unrated, judged to be of comparable quality by the sub-adviser. The fund may also invest in higher quality debt securities.Under normal conditions, the duration of the fund will generally vary between three and 20 years. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates. The longer a security’s duration, the more sensitive it will be to changes in interest rates. The fund does not limit the maturity of the securities in which it invests. The maturity of a fixed-income security is the measure of time remaining until the final payment on the security is due. However, under normal circumstances, the fund may focus on longer-term maturities in an effort to capture the higher yields generally associated with such maturities. The fund may invest more than 25% of its net assets in securities relating to one political subdivision, such as any state or U.S. territory. The fund may, but is not required to, invest in derivative instruments such as options and futures for speculative, hedging, or duration management purposes. The fund may also invest in exchange-traded funds (“ETFs”) as well as municipal bond closed-end funds. The fund may invest in privately issued securities, including those that are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended. The fund is non-diversified.

Transamerica High Yield Muni Investment Strategy - Retail Class [Member] - Transamerica High Yield Muni

Oct. 31, 2025

<span style="color:#000000;font-family:Times New Roman;font-size:10pt;font-weight:bold;margin-left:0%;">Principal Investment Strategies:</span>

Strategy Narrative [Text Block]

Under normal circumstances, the fund’s sub-adviser, Belle Haven Investments, L.P. (the “sub-adviser”), invests at least 80% of the fund’s net assets (plus the amount of borrowings, if any, for investment purposes) in municipal fixed-income securities the interest from which is exempt from federal income tax and the federal alternative minimum tax (“AMT”) applicable to individuals. Interest income from some of the municipal obligations in which the fund may invest may be subject to the AMT. The fund primarily invests in “high yield” municipal bonds under normal market conditions. For this purpose, “high yield” municipal bonds are those rated medium to lower grade. The fund normally invests primarily in general obligation and revenue bonds issued by U.S. municipal issuers, as well as issuers in U.S. territories and possessions. The fund may invest 25% or more of its total net assets in any sector or sub-sector of the municipal bond market. The fund pursues an actively managed, total return strategy that seeks to identify inefficiencies in the municipal bond market. The sub-adviser’s investment process is engineered to seek to exploit mispricing that the sub-adviser aims to identify at the issuer, credit, industry, security and/or maturity level based on macro-economic and fundamental analysis. Analysis is also used to determine the fund’s yield curve positioning. Investment decisions are made by the sub-adviser in an effort to maximize total return while balancing portfolio risk. Medium grade municipal bonds are those rated “A” to “BBB” by Standard & Poor’s Rating Services (“S&P”). Lower-grade municipal bonds (commonly known as “junk bonds”) are those rated below “Baa” by Moody’s Investors Service, Inc. (“Moody’s”) or lower than “BBB” by S&P or Fitch, Inc. (“Fitch”) or comparable ratings by other nationally recognized rating organizations (or, in the case of unrated securities, determined by the sub-adviser to be of comparable quality). The fund has the flexibility to invest the remainder of its assets in a broad array of issuers across the credit spectrum. The fund may also invest up to 15% of its net assets in municipal bonds that are distressed securities. Distressed securities are securities that are the subject of bankruptcy proceedings or are rated in the lowest rating categories by at least one independent rating agency (“CC” or lower by S&P or Fitch or “Ca” or lower by Moody’s), or if unrated, judged to be of comparable quality by the sub-adviser. The fund may also invest in higher quality debt securities.Under normal conditions, the duration of the fund will generally vary between three and 20 years. Duration is a measure used to determine the sensitivity of a security’s price to changes in interest rates. The longer a security’s duration, the more sensitive it will be to changes in interest rates. The fund does not limit the maturity of the securities in which it invests. The maturity of a fixed-income security is the measure of time remaining until the final payment on the security is due. However, under normal circumstances, the fund may focus on longer-term maturities in an effort to capture the higher yields generally associated with such maturities. The fund may invest more than 25% of its net assets in securities relating to one political subdivision, such as any state or U.S. territory. The fund may, but is not required to, invest in derivative instruments such as options and futures for speculative, hedging, or duration management purposes. The fund may also invest in exchange-traded funds (“ETFs”) as well as municipal bond closed-end funds. The fund may invest in privately issued securities, including those that are normally purchased pursuant to Rule 144A or Regulation S promulgated under the Securities Act of 1933, as amended. The fund is non-diversified.