v3.26.1
Shareholder Report, Average Annual Return (Details) 74200166100_Putnam Sustainable Future Fund_Class A_TSR Annual {Class A}
 12 Months Ended 60 Months Ended 120 Months Ended
Apr. 30, 2026
Apr. 30, 2026
Apr. 30, 2026
Class A      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Class A (with sales charge)    
Average Annual Return, Percent 6.18% (1.38%) 8.25%
Without Sales Load [Member] | Class A      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Class A    
Average Annual Return, Percent 12.66% (0.20%) 8.89%
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.