v3.26.1
Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
S&P 500 Index - Total Return (reflects no deduction for fees, expenses, or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 17.88% 14.42% 14.82%
Russell 1000 Value Index - Total Return (reflects no deduction for fees, expenses, or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 15.91% 11.33% 10.53%
Russell 3000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 17.15% 13.15% 14.29%
Russell 2500 Index-Total Return (reflects no deduction for fees, expenses, or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 11.91% 7.26% 10.40%
Russell 1000 Index-Total Return (reflects no deduction for fees, expenses, or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 17.37% 13.59% 14.59%
Russell 1000 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 18.56% 15.32% 18.13%
Russell 2500 Growth Index-Total Return (reflects no deduction for fees, expenses, or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 10.31% 2.98% 10.55%
Thornburg American Opportunities Fund - Class I      
Prospectus [Line Items]      
Average Annual Return, Percent (0.50%) 4.58% 8.09%
Thornburg American Opportunities Fund - Class I | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent (0.50%) 2.91% 7.09%
Thornburg American Opportunities Fund - Class I | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent (0.30%) 3.17% 6.30%
Thornburg Focus Growth Fund - Class I      
Prospectus [Line Items]      
Average Annual Return, Percent 4.82% (0.79%) 7.74%
Thornburg Focus Growth Fund - Class I | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent 4.82% (2.30%) 6.54%
Thornburg Focus Growth Fund - Class I | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent 2.85% (0.54%) 6.27%