v3.26.1
Shareholder Fees
Aug. 20, 2026
Thornburg Investment Income Builder Fund - Class A  
Prospectus [Line Items]  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.50%
Maximum Deferred Sales Charge (as a percentage) 0.00% [1]
Thornburg Investment Income Builder Fund - Class C  
Prospectus [Line Items]  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 0.00%
Maximum Deferred Sales Charge (as a percentage) 1.00% [2]
Thornburg Investment Income Builder Fund - Class I  
Prospectus [Line Items]  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 0.00%
Maximum Deferred Sales Charge (as a percentage) 0.00%
Thornburg Investment Income Builder Fund - Class R6  
Prospectus [Line Items]  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 0.00%
Maximum Deferred Sales Charge (as a percentage) 0.00%
Thornburg Summit Fund - Class A  
Prospectus [Line Items]  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 4.50%
Maximum Deferred Sales Charge (as a percentage) 0.00% [3]
Thornburg Summit Fund - Class I  
Prospectus [Line Items]  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) 0.00%
Maximum Deferred Sales Charge (as a percentage) 0.00%
[1] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.
[2] Imposed only on redemptions of Class C shares within 12 months of purchase.
[3] Up to a 1.00% contingent deferred sales charge (CDSC) is imposed on redemptions of any part or all of a purchase of $1 million or more within 12 months of purchase.