Shareholder Report, Average Annual Return (Details) 74200166100_Putnam Sustainable Future Fund_Class C_TSR Annual {Class C}

12 Months Ended

60 Months Ended

120 Months Ended

Apr. 30, 2026

Apr. 30, 2026

Apr. 30, 2026

Class C

Average Annual Return [Line Items]

Line Graph and Table Measure Name

Class C (with sales charge)

Average Annual Return, Percent

10.88%

(0.95%)

8.23%

Without Sales Load [Member] | Class C

Average Annual Return [Line Items]

Line Graph and Table Measure Name

Class C

Average Annual Return, Percent

11.83%

(0.95%)

8.23%

Russell 3000 Index [Member]

Average Annual Return [Line Items]

Line Graph and Table Measure Name

Russell 3000 Index

Average Annual Return, Percent

31.01%

11.91%

14.75%

Russell Midcap Growth Index [Member]

Average Annual Return [Line Items]

Line Graph and Table Measure Name

Russell Midcap Growth Index

Average Annual Return, Percent

12.86%

5.54%

12.40%

Putnam Sustainable Future Linked Benchmark [Member]

Average Annual Return [Line Items]

Line Graph and Table Measure Name

^[1]

Putnam Sustainable Future Linked Benchmark†

Average Annual Return, Percent

^[1]

12.86%

5.54%

11.32%

[1]

†	The Putnam Sustainable Future Linked Benchmark represents the performance of the Russell 3000 Value Index through March 20, 2018, and the performance of the Russell Midcap Growth Index thereafter.