v3.25.4
Average Annual Total Returns
 12 Months Ended 60 Months Ended 92 Months Ended 94 Months Ended 120 Months Ended 141 Months Ended 327 Months Ended 345 Months Ended 422 Months Ended
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THIRD AVENUE VALUE FUND Institutional Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Institutional Class Before Taxes                  
Average Annual Return, Percent   35.46% 18.00%     11.04%       10.92%
Performance Inception Date Nov. 01, 1990                  
THIRD AVENUE VALUE FUND Institutional Class | After Taxes on Distributions                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions                  
Average Annual Return, Percent   33.36% 16.31%     9.39%       9.57%
Performance Inception Date Nov. 01, 1990                  
THIRD AVENUE VALUE FUND Institutional Class | After Taxes on Distributions and Sales                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions and Sale of Fund Shares                  
Average Annual Return, Percent   22.49% 14.24%     8.56%       9.18%
Performance Inception Date Nov. 01, 1990                  
THIRD AVENUE VALUE FUND Institutional Class | MSCI World Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [1]         9.05%          
THIRD AVENUE VALUE FUND Investor Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Investor Class Before Taxes                  
Average Annual Return, Percent   35.15% 17.70%     10.76%       8.35%
Performance Inception Date Dec. 31, 2009                  
THIRD AVENUE VALUE FUND Investor Class | MSCI World Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [1]         11.27%          
THIRD AVENUE VALUE FUND Z Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Z Class Before Taxes                  
Average Annual Return, Percent   35.56% 18.11%           10.71%
Performance Inception Date Mar. 01, 2018                  
THIRD AVENUE VALUE FUND Z Class | MSCI World Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [1]   21.60% 12.66%   12.22% 12.74%        
Performance Inception Date Mar. 01, 2018                  
THIRD AVENUE SMALL-CAP VALUE FUND Institutional Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Institutional Class Before Taxes                  
Average Annual Return, Percent   14.04% 12.20%     9.82%     8.73%  
Performance Inception Date Apr. 01, 1997                  
THIRD AVENUE SMALL-CAP VALUE FUND Institutional Class | After Taxes on Distributions                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions                  
Average Annual Return, Percent   13.07% 10.06%     7.72%     7.30%  
Performance Inception Date Apr. 01, 1997                  
THIRD AVENUE SMALL-CAP VALUE FUND Institutional Class | After Taxes on Distributions and Sales                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions and Sale of Fund Shares                  
Average Annual Return, Percent   9.03% 9.44%     7.52%     7.16%  
Performance Inception Date Apr. 01, 1997                  
THIRD AVENUE SMALL-CAP VALUE FUND Institutional Class | MSCI USA All Cap Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI USA All Cap Index (reflects no deductions for fees, expenses, or taxes)                  
THIRD AVENUE SMALL-CAP VALUE FUND Institutional Class | MSCI USA Small Cap Value Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI USA Small Cap Value Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [2]         9.71%          
THIRD AVENUE SMALL-CAP VALUE FUND Investor Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Investor Class Before Taxes                  
Average Annual Return, Percent   13.71% 11.92%     9.55%     9.11%  
Performance Inception Date Dec. 31, 2009                  
THIRD AVENUE SMALL-CAP VALUE FUND Investor Class | MSCI USA All Cap Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI USA All Cap Index (reflects no deductions for fees, expenses, or taxes)                  
THIRD AVENUE SMALL-CAP VALUE FUND Investor Class | MSCI USA Small Cap Value Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI USA Small Cap Value Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [2]         10.66%          
THIRD AVENUE SMALL-CAP VALUE FUND Z Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Z Class Before Taxes                  
Average Annual Return, Percent   14.11% 12.31%         8.48%  
Performance Inception Date Mar. 01, 2018                  
THIRD AVENUE SMALL-CAP VALUE FUND Z Class | MSCI USA All Cap Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI USA All Cap Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [2]   17.27% 13.29%   13.88% 14.39%        
Performance Inception Date Mar. 01, 2018                  
THIRD AVENUE SMALL-CAP VALUE FUND Z Class | MSCI USA Small Cap Value Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI USA Small Cap Value Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [2]   10.80% 10.09%   8.22% 9.63%        
Performance Inception Date Mar. 01, 2018                  
THIRD AVENUE REAL ESTATE VALUE FUND Institutional Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Institutional Class Before Taxes                  
Average Annual Return, Percent   11.62% 8.58%     5.68%   8.96%    
Performance Inception Date Sep. 17, 1998                  
THIRD AVENUE REAL ESTATE VALUE FUND Institutional Class | After Taxes on Distributions                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions                  
Average Annual Return, Percent   10.16% 6.80%     3.93%   7.59%    
Performance Inception Date Sep. 17, 1998                  
THIRD AVENUE REAL ESTATE VALUE FUND Institutional Class | After Taxes on Distributions and Sales                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions and Sale of Fund Shares                  
Average Annual Return, Percent   7.68% 6.46%     4.17% [3]   7.41%    
Performance Inception Date Sep. 17, 1998                  
THIRD AVENUE REAL ESTATE VALUE FUND Institutional Class | MSCI World Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [4]         8.27%          
THIRD AVENUE REAL ESTATE VALUE FUND Institutional Class | MSCI ACWI IMI Core Real Estate Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI ACWI IMI Core Real Estate Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [4]         7.64%          
THIRD AVENUE REAL ESTATE VALUE FUND Investor Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Investor Class Before Taxes                  
Average Annual Return, Percent   11.33% 8.31%     5.41%   7.06%    
Performance Inception Date Dec. 31, 2009                  
THIRD AVENUE REAL ESTATE VALUE FUND Investor Class | MSCI World Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [4]         11.27%          
THIRD AVENUE REAL ESTATE VALUE FUND Investor Class | MSCI ACWI IMI Core Real Estate Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI ACWI IMI Core Real Estate Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [4]         6.40%          
THIRD AVENUE REAL ESTATE VALUE FUND Z Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Z Class Before Taxes                  
Average Annual Return, Percent   11.71% 8.68%       4.41%    
Performance Inception Date Mar. 01, 2018                  
THIRD AVENUE REAL ESTATE VALUE FUND Z Class | MSCI World Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [4]   21.60% 12.66%   12.22% 12.74%        
Performance Inception Date Mar. 01, 2018                  
THIRD AVENUE REAL ESTATE VALUE FUND Z Class | MSCI ACWI IMI Core Real Estate Index (reflects no deductions for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI ACWI IMI Core Real Estate Index (reflects no deductions for fees, expenses, or taxes)                  
Average Annual Return, Percent [4]   10.90% 3.49%   3.86% 4.37%        
Performance Inception Date Mar. 01, 2018                  
Third Avenue International Real Estate Value Fund Institutional Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Institutional Class Before Taxes                  
Average Annual Return, Percent   25.56% 5.54%     7.08% 5.95%      
Performance Inception Date Mar. 19, 2014                  
Third Avenue International Real Estate Value Fund Institutional Class | After Taxes on Distributions                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions                  
Average Annual Return, Percent   24.84% 5.06%     6.08% 4.99%      
Performance Inception Date Mar. 19, 2014                  
Third Avenue International Real Estate Value Fund Institutional Class | After Taxes on Distributions and Sales                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] After Taxes on Distributions and Sale of Fund Shares                  
Average Annual Return, Percent   15.56% 4.34%     5.34% 4.41%      
Performance Inception Date Mar. 19, 2014                  
Third Avenue International Real Estate Value Fund Institutional Class | MSCI World ex USA Index (reflects no deduction for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World ex USA Index (reflects no deduction for fees, expenses, or taxes)                  
Average Annual Return, Percent [5]       7.15%            
Third Avenue International Real Estate Value Fund Institutional Class | MSCI ACWI ex USA IMI Core Real Estate Index (reflects no deduction for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI ACWI ex USA IMI Core Real Estate Index (reflects no deduction for fees, expenses, or taxes)                  
Average Annual Return, Percent [5]       2.99%            
Third Avenue International Real Estate Value Fund Z Class                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] Z Class Shares Before Taxes                  
Average Annual Return, Percent   25.49% 5.55%     5.71%      
Performance Inception Date Apr. 20, 2018                  
Third Avenue International Real Estate Value Fund Z Class | MSCI World ex USA Index (reflects no deduction for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI World ex USA Index (reflects no deduction for fees, expenses, or taxes)                  
Average Annual Return, Percent [5]   32.55% 10.04% 8.28%   9.11%        
Performance Inception Date Apr. 20, 2018                  
Third Avenue International Real Estate Value Fund Z Class | MSCI ACWI ex USA IMI Core Real Estate Index (reflects no deduction for fees, expenses, or taxes)                    
Prospectus [Line Items]                    
Average Annual Return, Label [Optional Text] MSCI ACWI ex USA IMI Core Real Estate Index (reflects no deduction for fees, expenses, or taxes)                  
Average Annual Return, Percent [5]   22.14% 0.36% 0.50%   3.03%        
Performance Inception Date Apr. 20, 2018                  
[1] The MSCI World Index captures large and mid-cap representation across 23 Developed Markets countries. With 1,320 constituents, the MSCI World Index covers approximately 85% of the free float-adjusted market capitalization in each country. The MSCI World Index is not a security that can be purchased or sold, and its total returns are reflective of unmanaged portfolios. It is not possible to invest directly in an unmanaged index.
[2] The MSCI USA All Cap Index captures broad US equity coverage. The index includes 3,356 constituents across large, mid, small and micro capitalizations, representing about 99% of the US equity universe. The Fund will also use the MSCI USA Small Cap Value Index as a secondary benchmark. The MSCI USA Small Cap Value Index captures small cap securities exhibiting overall value style characteristics across the US equity markets. The value investment style characteristics for index construction are defined using three variables: book value to price, 12-month forward earnings to price and dividend yield. The MSCI USA All Cap Index and the MSCI USA Small Cap Value Index are not securities that can be purchased or sold, and their total returns are reflective of unmanaged portfolios. The returns include reinvestment of all distributions. It is not possible to invest directly in an unmanaged index.
[3] The Return After Taxes on Distributions and Sale of Fund Shares is higher than the Return After Taxes on Distributions because of realized losses that would have been sustained upon the sale of Fund shares immediately after the relevant periods.
[4] The MSCI World Index captures large and mid-cap representation across 23 Developed Markets countries. With 1,320 constituents, the MSCI World Index covers approximately 85% of the free float-adjusted market capitalization in each country. The Fund will also use the MSCI ACWI IMI Core Real Estate Index as a secondary benchmark. The MSCI ACWI IMI Core Real Estate Index is a free float-adjusted market capitalization index that consists of large, mid and small-cap stocks across 23 Developed Markets and 24 Emerging Markets countries engaged in ownership, development and management of specific core property type real estate. The MSCI ACWI IMI Core Real Estate Index excludes companies, such as real estate services and real estate financing companies, that do not own properties. The MSCI World Index and the MSCI ACWI IMI Core Real Estate Index are not securities that can be purchased or sold, and their total returns are reflective of unmanaged portfolios. The returns include reinvestment of all distributions. It is not possible to invest directly in an unmanaged index.
[5] The MSCI World ex USA Index captures large and mid-cap representation across 22 of 23 Developed Market countries, excluding the United States. With 776 constituents, the MSCI World ex USA Index covers approximately 85% of the free float-adjusted market capitalization in each country. The Fund will also use the MSCI ACWI ex US IMI Core Real Estate Index as a secondary benchmark. The MSCI ACWI ex USA IMI Core Real Estate Index is a free float-adjusted market capitalization index that consists of large, mid and small-cap stocks across 22 Developed Markets and 24 Emerging Markets countries engaged in the ownership, development and management of specific core property type real estate. The MSCI ACWI ex USA IMI Core Real Estate Index excludes companies, such as real estate services and real estate financing companies, that do not own properties. The MSCI World ex USA Index and the MSCI ACWI ex USA IMI Core Real Estate Index are not securities that can be purchased or sold, and their total returns are reflective of unmanaged portfolios. The returns include reinvestment of all distributions. It is not possible to invest directly in an unmanaged index.