v3.25.2
S000094551 [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2024
Dec. 31, 2024
Dec. 31, 2024
Bloomberg Municipal Bond Index (no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 1.05% 0.99% 2.25%
Putnam Tax Exempt Income Fund - Class R6      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 2.50% 1.20% 2.46%
Putnam Tax Exempt Income Fund - Class R6 | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 2.50% 1.10% 2.30%
Putnam Tax Exempt Income Fund - Class R6 | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 2.92% 1.358% 2.58%
[1]
Performance for class R6 shares prior to their inception (5/22/18) is derived from the historical performance of class Y shares and has not been adjusted for the lower investor servicing fees applicable to class R6 shares; had it been adjusted, returns would have been higher.