The fund invests mainly in mortgages, mortgage-related fixed income securities and related derivatives that are either investment-grade or below-investment-grade in quality (sometimes referred to as “junk bonds”). Under normal circumstances, the fund invests at least 80% of its net assets in mortgages, mortgage-related fixed income securities and related derivatives (i.e., derivatives used to acquire exposure to, or whose underlying securities are, mortgages or mortgage-related securities). This policy may be changed only after 60 days’ notice to shareholders.

The fund expects to invest in lower-rated, higher-yielding mortgage-backed securities, including non-agency residential mortgage-backed securities (which may be backed by non-qualified or “sub-prime” mortgages), commercial mortgage-backed securities, collateralized mortgage obligations (including interest only, principal only, and other prepayment derivatives), and agency mortgage-backed securities. The fund currently has significant investment exposure to commercial mortgage backed securities. Non-agency (i.e., privately issued) securities typically are lower-rated and higher yielding than securities issued or backed by agencies such as Ginnie Mae, Fannie Mae or Freddie Mac. While the fund’s emphasis will be on mortgage-backed securities, the fund may also invest to a lesser extent in other types of asset-backed securities.

The Investment Manager may consider, among other factors, credit, interest rate, prepayment and liquidity risks, as well as general market conditions, when deciding whether to buy or sell investments.

The Investment Manager typically uses, to a significant extent, derivatives, including credit default swaps, interest rate swaps, total return swaps, to-be-announced (TBA) commitments, futures, options and swaptions on mortgage-backed securities and indices for both hedging and non-hedging purposes, including to obtain or adjust exposure to mortgage-backed securities. The fund’s investments in derivative instruments and other investments that provide exposure to the investment focus indicated in the fund’s 80% policy, or that provide exposure to one or more market risk factors associated with the investment focus indicated in the fund’s name, are included in the fund’s 80% basket.

Prospectus 2 [Member] Investment Strategy - Prospectus 2 - PUTNAM MORTGAGE OPPORTUNITIES FUND	May 31, 2026
Prospectus [Line Items]
Strategy [Heading]	Investments, risks, and performance Investments
Strategy Narrative [Text Block]	The fund invests mainly in mortgages, mortgage-related fixed income securities and related derivatives that are either investment-grade or below-investment-grade in quality (sometimes referred to as “junk bonds”). Under normal circumstances, the fund invests at least 80% of its net assets in mortgages, mortgage-related fixed income securities and related derivatives (i.e., derivatives used to acquire exposure to, or whose underlying securities are, mortgages or mortgage-related securities). This policy may be changed only after 60 days’ notice to shareholders. The fund expects to invest in lower-rated, higher-yielding mortgage-backed securities, including non-agency residential mortgage-backed securities (which may be backed by non-qualified or “sub-prime” mortgages), commercial mortgage-backed securities, collateralized mortgage obligations (including interest only, principal only, and other prepayment derivatives), and agency mortgage-backed securities. The fund currently has significant investment exposure to commercial mortgage backed securities. Non-agency (i.e., privately issued) securities typically are lower-rated and higher yielding than securities issued or backed by agencies such as Ginnie Mae, Fannie Mae or Freddie Mac. While the fund’s emphasis will be on mortgage-backed securities, the fund may also invest to a lesser extent in other types of asset-backed securities. The Investment Manager may consider, among other factors, credit, interest rate, prepayment and liquidity risks, as well as general market conditions, when deciding whether to buy or sell investments. The Investment Manager typically uses, to a significant extent, derivatives, including credit default swaps, interest rate swaps, total return swaps, to-be-announced (TBA) commitments, futures, options and swaptions on mortgage-backed securities and indices for both hedging and non-hedging purposes, including to obtain or adjust exposure to mortgage-backed securities. The fund’s investments in derivative instruments and other investments that provide exposure to the investment focus indicated in the fund’s 80% policy, or that provide exposure to one or more market risk factors associated with the investment focus indicated in the fund’s name, are included in the fund’s 80% basket.