| Form N-CSR Cover | 6 Months Ended |
| Dec. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | FORUM FUNDS |
| Entity Central Index Key | 0000315774 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| Shareholder Report | 6 Months Ended |
| Dec. 31, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | FORUM FUNDS |
| Entity Central Index Key | 0000315774 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| C000012491 | |
| Shareholder Report [Line Items] | |
| Fund Name | Auxier Focus Fund |
| Class Name | A Shares |
| Trading Symbol | AUXAX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Auxier Focus Fund for the period of July 1, 2024, to December 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | This semi-annual shareholder report contains important information about the Auxier Focus Fund for the period of July 1, 2024, to December 31, 2024. You can find additional information about the Fund at https://auxierasset.com/prospectus-and-reports. You can also request this information by contacting us at (877) 328-9437. |
| Additional Information Phone Number | (877) 328-9437 |
| Additional Information Website | https://auxierasset.com/prospectus-and-reports |
| Expenses [Text Block] | What were the Fund's costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment A shares Class $64 1.24% |
| Expenses Paid, Amount | $ 64 |
| Expense Ratio, Percent | 1.24% |
| AssetsNet | $ 281,432,100 |
| Holdings Count | Holding | 115 |
| Advisory Fees Paid, Amount | $ 850,185 |
| InvestmentCompanyPortfolioTurnover | 1% |
| Additional Fund Statistics [Text Block] | Fund Statistics Total Net Assets $281,432,100 # of Portfolio Holdings 115 Portfolio Turnover Rate 1% Investment Advisory Fees (Net of fees waived) $850,185 |
| Holdings [Text Block] | Asset Class Weightings (% of total investments) Value Value Common Stock 94.8% Preferred Stock 0.7% Corporate Non-Convertible Bonds 0.8% Money Market Fund 3.7% |
| Largest Holdings [Text Block] | Top Ten Holdings (% total investments) Microsoft Corp. 6.18% Mastercard, Inc., Class A 5.83% UnitedHealth Group, Inc. 5.01% The Kroger Co. 4.24% Philip Morris International, Inc. 3.82% The Bank of New York Mellon Corp. 3.81% Fidelity Investments Treasury Only Portfolio, Institutional Class, 4.38% 3.71% Visa, Inc., Class A 3.29% Bank of America Corp. 3.12% Alphabet, Inc., Class A 2.73% |
| C000112762 | |
| Shareholder Report [Line Items] | |
| Fund Name | Auxier Focus Fund |
| Class Name | Institutional |
| Trading Symbol | AUXIX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Auxier Focus Fund for the period of July 1, 2024, to December 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | This semi-annual shareholder report contains important information about the Auxier Focus Fund for the period of July 1, 2024, to December 31, 2024. You can find additional information about the Fund at https://auxierasset.com/prospectus-and-reports. You can also request this information by contacting us at (877) 328-9437. |
| Additional Information Phone Number | (877) 328-9437 |
| Additional Information Website | https://auxierasset.com/prospectus-and-reports |
| Expenses [Text Block] | What were the Fund's costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Institutional Shares $41 0.79% |
| Expenses Paid, Amount | $ 41 |
| Expense Ratio, Percent | 0.79% |
| AssetsNet | $ 281,432,100 |
| Holdings Count | Holding | 115 |
| Advisory Fees Paid, Amount | $ 850,185 |
| InvestmentCompanyPortfolioTurnover | 1% |
| Additional Fund Statistics [Text Block] | Fund Statistics Total Net Assets $281,432,100 # of Portfolio Holdings 115 Portfolio Turnover Rate 1% Investment Advisory Fees (Net of fees waived) $850,185 |
| Holdings [Text Block] | Asset Class Weightings (% of total investments) Value Value Common Stock 94.8% Preferred Stock 0.7% Corporate Non-Convertible Bonds 0.8% Money Market Fund 3.7% |
| Largest Holdings [Text Block] | Top Ten Holdings (% total investments) Microsoft Corp. 6.18% Mastercard, Inc., Class A 5.83% UnitedHealth Group, Inc. 5.01% The Kroger Co. 4.24% Philip Morris International, Inc. 3.82% The Bank of New York Mellon Corp. 3.81% Fidelity Investments Treasury Only Portfolio, Institutional Class, 4.38% 3.71% Visa, Inc., Class A 3.29% Bank of America Corp. 3.12% Alphabet, Inc., Class A 2.73% |
| C000012493 | |
| Shareholder Report [Line Items] | |
| Fund Name | Auxier Focus Fund |
| Class Name | Investor |
| Trading Symbol | AUXFX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Auxier Focus Fund for the period of July 1, 2024, to December 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | This semi-annual shareholder report contains important information about the Auxier Focus Fund for the period of July 1, 2024, to December 31, 2024. You can find additional information about the Fund at https://auxierasset.com/prospectus-and-reports. You can also request this information by contacting us at (877) 328-9437. |
| Additional Information Phone Number | (877) 328-9437 |
| Additional Information Website | https://auxierasset.com/prospectus-and-reports |
| Expenses [Text Block] | What were the Fund's costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Investor Shares $47 0.91% |
| Expenses Paid, Amount | $ 47 |
| Expense Ratio, Percent | 0.91% |
| AssetsNet | $ 281,432,100 |
| Holdings Count | Holding | 115 |
| Advisory Fees Paid, Amount | $ 850,185 |
| InvestmentCompanyPortfolioTurnover | 1% |
| Additional Fund Statistics [Text Block] | Fund Statistics Total Net Assets $281,432,100 # of Portfolio Holdings 115 Portfolio Turnover Rate 1% Investment Advisory Fees (Net of fees waived) $850,185 |
| Holdings [Text Block] | Asset Class Weightings (% of total investments) Value Value Common Stock 94.8% Preferred Stock 0.7% Corporate Non-Convertible Bonds 0.8% Money Market Fund 3.7% |
| Largest Holdings [Text Block] | Top Ten Holdings (% total investments) Microsoft Corp. 6.18% Mastercard, Inc., Class A 5.83% UnitedHealth Group, Inc. 5.01% The Kroger Co. 4.24% Philip Morris International, Inc. 3.82% The Bank of New York Mellon Corp. 3.81% Fidelity Investments Treasury Only Portfolio, Institutional Class, 4.38% 3.71% Visa, Inc., Class A 3.29% Bank of America Corp. 3.12% Alphabet, Inc., Class A 2.73% |
| Shareholder Report, Holdings (Details) | Dec. 31, 2024 |
| C000012491 | Microsoft Corp.None_594918104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.18% |
| C000012491 | Mastercard, Inc.NoneA_57636Q104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.83% |
| C000012491 | UnitedHealth Group, Inc.None_91324P102 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.01% |
| C000012491 | The Kroger Co.None_501044101 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.24% |
| C000012491 | Philip Morris International, Inc.None_718172109 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.82% |
| C000012491 | The Bank of New York Mellon Corp.None_064058100 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.81% |
| C000012491 | Fidelity Investments Treasury Only Portfolio, Institutional Class0.043775_31607A802 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.71% |
| C000012491 | Visa, Inc.NoneA_92826C839 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.29% |
| C000012491 | Bank of America Corp.None_060505104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.12% |
| C000012491 | Alphabet, Inc.NoneA_02079K305 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.73% |
| C000012491 | Financials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 27.80% |
| C000012491 | Health Care | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.40% |
| C000012491 | Consumer Staples | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.70% |
| C000012491 | Information Technology | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000012491 | Consumer Discretionary | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000012491 | Industrials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.90% |
| C000012491 | Energy | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000012491 | Consumer Cyclical | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000012491 | Materials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000012491 | Transportation | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000012491 | Communications | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000012491 | Common Stock | |
| Holdings [Line Items] | |
| Percent of Total Investments | 94.80% |
| C000012491 | Preferred Stock | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000012491 | Corporate Non-Convertible Bonds | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000012491 | Money Market Fund | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000112762 | Microsoft Corp.None_594918104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.18% |
| C000112762 | Mastercard, Inc.NoneA_57636Q104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.83% |
| C000112762 | UnitedHealth Group, Inc.None_91324P102 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.01% |
| C000112762 | The Kroger Co.None_501044101 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.24% |
| C000112762 | Philip Morris International, Inc.None_718172109 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.82% |
| C000112762 | The Bank of New York Mellon Corp.None_064058100 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.81% |
| C000112762 | Fidelity Investments Treasury Only Portfolio, Institutional Class0.043775_31607A802 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.71% |
| C000112762 | Visa, Inc.NoneA_92826C839 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.29% |
| C000112762 | Bank of America Corp.None_060505104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.12% |
| C000112762 | Alphabet, Inc.NoneA_02079K305 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.73% |
| C000112762 | Financials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 27.80% |
| C000112762 | Health Care | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.40% |
| C000112762 | Consumer Staples | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.70% |
| C000112762 | Information Technology | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000112762 | Consumer Discretionary | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000112762 | Industrials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.90% |
| C000112762 | Energy | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000112762 | Consumer Cyclical | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000112762 | Materials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000112762 | Transportation | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000112762 | Communications | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000112762 | Common Stock | |
| Holdings [Line Items] | |
| Percent of Total Investments | 94.80% |
| C000112762 | Preferred Stock | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000112762 | Corporate Non-Convertible Bonds | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000112762 | Money Market Fund | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
| C000012493 | Microsoft Corp.None_594918104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.18% |
| C000012493 | Mastercard, Inc.NoneA_57636Q104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.83% |
| C000012493 | UnitedHealth Group, Inc.None_91324P102 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 5.01% |
| C000012493 | The Kroger Co.None_501044101 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.24% |
| C000012493 | Philip Morris International, Inc.None_718172109 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.82% |
| C000012493 | The Bank of New York Mellon Corp.None_064058100 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.81% |
| C000012493 | Fidelity Investments Treasury Only Portfolio, Institutional Class0.043775_31607A802 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.71% |
| C000012493 | Visa, Inc.NoneA_92826C839 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.29% |
| C000012493 | Bank of America Corp.None_060505104 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.12% |
| C000012493 | Alphabet, Inc.NoneA_02079K305 | |
| Holdings [Line Items] | |
| Percent of Total Investments | 2.73% |
| C000012493 | Financials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 27.80% |
| C000012493 | Health Care | |
| Holdings [Line Items] | |
| Percent of Total Investments | 19.40% |
| C000012493 | Consumer Staples | |
| Holdings [Line Items] | |
| Percent of Total Investments | 18.70% |
| C000012493 | Information Technology | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.80% |
| C000012493 | Consumer Discretionary | |
| Holdings [Line Items] | |
| Percent of Total Investments | 8.50% |
| C000012493 | Industrials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.90% |
| C000012493 | Energy | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.40% |
| C000012493 | Consumer Cyclical | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000012493 | Materials | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3% |
| C000012493 | Transportation | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000012493 | Communications | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.20% |
| C000012493 | Common Stock | |
| Holdings [Line Items] | |
| Percent of Total Investments | 94.80% |
| C000012493 | Preferred Stock | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| C000012493 | Corporate Non-Convertible Bonds | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.80% |
| C000012493 | Money Market Fund | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.70% |
