v3.26.3
Shareholder Report, Average Annual Return (Details) 74200172000_Putnam Strategic Intermediate Municipal Fund_Class C_TSR Annual {Class C}
 12 Months Ended 60 Months Ended 120 Months Ended
Jul. 31, 2026
Jul. 31, 2026
Jul. 31, 2026
Class C      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Class C (with sales charge)    
Average Annual Return, Percent 3.51% 0.42% 1.63%
Without Sales Load [Member] | Class C      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Class C    
Average Annual Return, Percent 4.51% 0.42% 1.63%
Bloomberg Municipal Bond Index [Member]      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Bloomberg Municipal Bond Index    
Average Annual Return, Percent 5.27% 0.51% 1.95%
Putnam Strategic Intermediate Municipal Linked Benchmark [Member]      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Putnam Strategic Intermediate Municipal Linked Benchmark    
Average Annual Return, Percent [1] 3.74% 0.77% 2.00%
Bloomberg 3-15 Year Blend Municipal Bond Index [Member]      
Average Annual Return [Line Items]      
Line Graph and Table Measure Name Bloomberg 3-15 Year Blend Municipal Bond Index    
Average Annual Return, Percent 3.74% 0.77% 1.93%
[1]
† The Putnam Strategic Intermediate Municipal Linked Benchmark represents the performance of the Bloomberg Municipal Bond Index through August 27, 2020, and the performance of the Bloomberg 3-15 Year Blend Municipal Bond Index thereafter.