S000093658 [Member] Fees and Expenses - Putnam Sustainable Retirement 2070 Fund	Jul. 28, 2025 USD ($)
Prospectus [Line Items]
Expense Heading [Optional Text]	Fees and expenses
Expense Narrative [Text Block]	The following tables describe the fees and expenses you may pay if you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds. More information about these and other discounts is available from your financial professional and in How do I buy fund shares? beginning on page 56 of the fund’s prospectus, in the Appendix to the fund’s prospectus, and in How to buy shares beginning on page II‑3 of the fund’s statement of additional information (“SAI”).
Expense Breakpoint Discounts [Text]	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds.
Expense Breakpoint, Minimum Investment Required [Amount]	$ 50,000
Other Expenses, New Fund, Based on Estimates [Text]	Other expenses are estimated based on the expenses the fund expects to incur for the current fiscal year and include 4.50% of non‑recurring costs related to commencement of the fund’s operations. Actual expenses may differ from estimates.Estimated amounts for the current fiscal year. Actual expenses may differ from estimates.
Shareholder Fees Caption [Optional Text]	Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Optional Text]	Annual fund operating expenses (expenses you pay each year as a percentage of the value of your investment)
Expense Example [Heading]	Example
Expense Example Narrative [Text Block]	The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then, except as indicated, redeem all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. The example takes into account the expense reimbursement described above for the 1‑year period. Your actual costs may be higher or lower.
Portfolio Turnover [Heading]	Portfolio turnover
Portfolio Turnover [Text Block]	The fund pays transaction-related costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher turnover rate may indicate higher transaction costs and may result in higher taxes when the fund’s shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or the above example, affect fund performance. The fund’s turnover rate will be available after the fund completes its first fiscal year.

S000093658 [Member] Fees and Expenses - Putnam Sustainable Retirement 2070 Fund

Jul. 28, 2025

USD ($)

Fees and expenses

The following tables describe the fees and expenses you may pay if you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds. More information about these and other discounts is available from your financial professional and in How do I buy fund shares? beginning on page 56 of the fund’s prospectus, in the Appendix to the fund’s prospectus, and in How to buy shares beginning on page II‑3 of the fund’s statement of additional information (“SAI”).

Expense Breakpoint Discounts [Text]

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds.

Expense Breakpoint, Minimum Investment Required [Amount]

$ 50,000

Other Expenses, New Fund, Based on Estimates [Text]

Other expenses are estimated based on the expenses the fund expects to incur for the current fiscal year and include 4.50% of non‑recurring costs related to commencement of the fund’s operations. Actual expenses may differ from estimates.Estimated amounts for the current fiscal year. Actual expenses may differ from estimates.

Shareholder Fees Caption [Optional Text]

Shareholder fees (fees paid directly from your investment)

Operating Expenses Caption [Optional Text]

Annual fund operating expenses (expenses you pay each year as a percentage of the value of your investment)

Expense Example [Heading]

Example

Expense Example Narrative [Text Block]

The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then, except as indicated, redeem all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. The example takes into account the expense reimbursement described above for the 1‑year period. Your actual costs may be higher or lower.

Portfolio Turnover [Heading]

Portfolio turnover

Portfolio Turnover [Text Block]

The fund pays transaction-related costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher turnover rate may indicate higher transaction costs and may result in higher taxes when the fund’s shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or the above example, affect fund performance. The fund’s turnover rate will be available after the fund completes its first fiscal year.