S000051718 [Member] Investment Risks - Putnam Sustainable Retirement 2060 Fund	Jul. 31, 2025
Substantial shareholder risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Substantial shareholder risk: Certain accounts or affiliates of the Investment Manager, including other funds advised by the Investment Manager or third parties, may from time to time own (beneficially or of record) or control a substantial amount of the fund’s shares, including through seed capital arrangements. Such shareholders may at times be considered to control the fund. Dispositions of a large number of shares by these shareholders may adversely affect the fund’s liquidity and net assets. These redemptions may also force the fund to sell securities, which may increase the fund’s brokerage costs.
Market risks [Member]
Prospectus [Line Items]
Risk [Text Block]	Market risk: A fund’s allocation of assets among asset classes may hurt performance. The value of investments in the fund’s portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general economic, political or financial market conditions, investor sentiment and market perceptions, government actions, geopolitical events or changes, outbreaks of infectious illnesses or other widespread public health issues, and factors related to a specific issuer, asset class, geography, industry or sector. These and other factors may lead to increased volatility and reduced liquidity in the fund’s portfolio holdings, may negatively impact the fund’s performance, and may exacerbate other risks to which the fund is subject.
Common stock risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Common stock risk: Common stock represents an ownership interest in a company. The value of a company’s stock may fall or fail to rise as a result of factors directly relating to that company, such as decisions made by its management or lower demand for the company’s products or services. A stock’s value may also fall because of factors affecting not just the company, but also other companies in the same industry or in a number of different industries, such as increases in production costs. Growth investing risk: Growth stocks may be more susceptible to earnings disappointments, and the market may not favor growth-style investing. Value investing risk: Value stocks may fail to rebound, and the market may not favor value-style investing. Companies whose stocks the Investment Manager believes are undervalued by the market may have experienced adverse business developments or may be subject to special risks that have caused their stocks to be out of favor. Small and midsize companies risk: Stocks of small and midsize companies often trade in smaller volumes, and their prices may fluctuate more than stocks of larger companies. Stocks of these companies may therefore be more vulnerable to adverse developments than those of larger companies.
Fixed income investments risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Fixed income investments risk: The risks associated with fixed income investments include interest rate risk, which is the risk that the value of the fund’s investments is likely to fall if interest rates rise. Fixed income investments are also subject to credit risk, which is the risk that issuers of the fund’s investments may default on payment of interest or principal. Fixed income investments may be more susceptible to downgrades or defaults during economic downturns or other periods of economic stress. Default risk is generally higher for non-qualified mortgages. Interest rate risk is generally greater for longer-term bonds, and credit risk is generally greater for below-investment-grade bonds (sometimes referred to as “junk bonds”), which can be more sensitive to changes in markets, credit conditions, and interest rates, and may be considered speculative. Mortgage-backed investments, unlike traditional debt investments, are also subject to prepayment risk, which means that they may increase in value less than other bonds when interest rates decline and decline in value more than other bonds when interest rates rise. The fund may have to invest the proceeds from prepaid investments, including mortgage-backed investments, in other investments with less attractive terms and yields. The fund’s investments in mortgage-backed securities, and in certain other securities and derivatives, may be or become illiquid.
Foreign investments risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Foreign investments risk: The value of international investments traded in foreign currencies may be adversely impacted by fluctuations in exchange rates. International investments, particularly investments in emerging markets, may carry risks associated with potentially less stable economies or governments (such as the risk of seizure by a foreign government, the imposition of economic sanctions or currency or other restrictions, or high levels of inflation), and may be or become illiquid.
Derivatives risks [Member]
Prospectus [Line Items]
Risk [Text Block]	Derivatives risk: The fund may have exposure to derivatives such as futures, options, swap contracts, and certain foreign currency transactions and warrants, for both hedging and investment purposes. An underlying fund’s use of derivatives may increase the risks of investing in the underlying fund by increasing investment exposure (which may be considered leverage) or, in the case of many over-the-counter instruments, because of the potential inability to terminate or sell derivative positions and the potential failure of the other party to the instrument to meet its obligations. The risk of a party failing to meet its obligations may increase if the underlying fund has significant exposure to that counterparty. The value of derivatives may move in unexpected ways due to unanticipated market movements, the use of leverage, imperfect correlation between the derivative instrument and the reference asset, or other factors, especially in unusual market conditions, and volatility in the value of derivatives could adversely impact the underlying fund’s returns, obligations and exposures. Derivatives are also subject to other risks, including liquidity risk (e.g., liquidity demands arising from the requirement to make payments to a derivative counterparty), operational risk (e.g., settlement issues or system failures) and legal risk (e.g., insufficient legal documentation or contract enforceability issues).
Alternative strategies risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Alternative strategies risk: In addition to risks associated with more traditional investments (e.g., market risk, credit risk, etc.), the fund’s investments in underlying funds that pursue alternative strategies (such as private credit and private and public real estate strategies) are subject to additional risks, which may be significant, and may expose the underlying fund to potentially significant fluctuations in value. The underlying funds’ alternative strategies may not work as intended, resulting in potentially significant losses for the underlying fund. Furthermore, alternative strategies may employ leverage, involve short positions, and/or focus on narrow segments of the market, which may magnify the underlying fund’s overall risks and volatility. Alternative strategies also may expose the underlying fund to additional liquidity risk and to valuation risk (the risk that the sale price the underlying fund could receive for a portfolio security may differ from the underlying fund’s valuation of the security).
Management and operational risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Management and operational risk: There is no guarantee that the investment techniques, analyses, or judgments that the Investment Manager applies in making investment decisions for the fund will produce the intended outcome or that the investments selected for the fund will perform as well as other securities that were not selected for the fund. If the quantitative models or data that are used in managing the underlying fund prove to be incorrect or incomplete, investment decisions made in reliance on the models or data may not produce the desired results and the fund may realize losses. The Investment Manager, or the fund’s other service providers, may experience disruptions or operating errors that could negatively impact the fund. The fund may not achieve its goal, and it is not intended to be a complete investment program. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Allocation risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Allocation risk: The fund’s allocation of assets among asset classes and the underlying funds may hurt performance. An underlying fund may change its investment program or policies without the fund’s approval, which could require the fund to reduce or eliminate its allocation to the underlying fund at an unfavorable time.
Risk Lose Money [Member]
Prospectus [Line Items]
Risk [Text Block]	It is important to understand that you can lose money by investing in the fund.
Risk Not Insured [Member]
Prospectus [Line Items]
Risk [Text Block]	An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.