| Form N-CSR Cover | 6 Months Ended |
| Jun. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | BNY Mellon Investment Funds III |
| Entity Central Index Key | 0000053808 |
| Document Period End Date | Jun. 30, 2024 |
| Shareholder Report | 6 Months Ended | |
| Jun. 30, 2024 USD ($) | ||
| Shareholder Report [Line Items] | ||
| Document Type | N-CSRS | |
| Amendment Flag | false | |
| Registrant Name | BNY Mellon Investment Funds III | |
| Entity Central Index Key | 0000053808 | |
| Document Period End Date | Jun. 30, 2024 | |
| Class A - DQIAX | ||
| Shareholder Report [Line Items] | ||
| Fund Name | BNY Mellon High Yield Fund | |
| Class Name | Class A | |
| Trading Symbol | DPLTX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| Class C - DQICX | ||
| Shareholder Report [Line Items] | ||
| Fund Name | BNY Mellon High Yield Fund | |
| Class Name | Class C | |
| Trading Symbol | PTHIX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| Class I - DQIRX | ||
| Shareholder Report [Line Items] | ||
| Fund Name | BNY Mellon High Yield Fund | |
| Class Name | Class I | |
| Trading Symbol | DLHRX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| BNY Mellon High Yield Fund | Class A - DQIAX | ||
| Shareholder Report [Line Items] | ||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about BNY Mellon High Yield Fund (the “Fund”) for the period of January 1, 2024 to June 30, 2024. You can find additional information about the Fund at im.bnymellon.com/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info bnymellon.com. | |
| Additional Information [Text Block] | You can find additional information about the Fund at im.bnymellon.com/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bnymellon.com. | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bnymellon.com | |
| Additional Information Website | im.bnymellon.com/literaturecenter | |
| Expenses [Text Block] | What were the Fund’s costs for the last six months? (based on a hypothetical $10,000 investment) Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class A * $48 0.95% ** * During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. ** Annualized | |
| Expenses Paid, Amount | $ 48 | [1] |
| Expense Ratio, Percent | 0.95% | [1],[2] |
| Net Assets | $ 563,000,000 | |
| Holdings Count | 338 | |
| Portfolio Turnover | 57.20% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 6/30/24) Fund Size (Millions) Number of Holdings Portfolio Turnover $563 338 57.20% | |
| Holdings [Text Block] | Portfolio Holdings (as of 6/30/24) Allocation of Holdings (Based on Net Assets) Sector Allocation (Based on Net Assets) | |
| Updated Prospectus Web Address | im.bnymellon.com/literaturecenter | |
| BNY Mellon High Yield Fund | Class C - DQICX | ||
| Shareholder Report [Line Items] | ||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about BNY Mellon High Yield Fund (the “Fund”) for the period of January 1, 2024 to June 30, 2024. You can find additional information about the Fund at im.bnymellon.com/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info bnymellon.com. | |
| Additional Information [Text Block] | You can find additional information about the Fund at im.bnymellon.com/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bnymellon.com. | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bnymellon.com | |
| Additional Information Website | im.bnymellon.com/literaturecenter | |
| Expenses [Text Block] | What were the Fund’s costs for the last six months? (based on a hypothetical $10,000 investment) Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class C * $86 1.70% ** * During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. ** Annualized | |
| Expenses Paid, Amount | $ 86 | [3] |
| Expense Ratio, Percent | 1.70% | [3],[4] |
| Net Assets | $ 563,000,000 | |
| Holdings Count | 338 | |
| Portfolio Turnover | 57.20% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 6/30/24) Fund Size (Millions) Number of Holdings Portfolio Turnover $563 338 57.20% | |
| Holdings [Text Block] | Portfolio Holdings (as of 6/30/24) Allocation of Holdings (Based on Net Assets) Sector Allocation (Based on Net Assets) | |
| Updated Prospectus Web Address | im.bnymellon.com/literaturecenter | |
| BNY Mellon High Yield Fund | Class I - DQIRX | ||
| Shareholder Report [Line Items] | ||
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about BNY Mellon High Yield Fund (the “Fund”) for the period of January 1, 2024 to June 30, 2024. You can find additional information about the Fund at im.bnymellon.com/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info bnymellon.com. | |
| Additional Information [Text Block] | You can find additional information about the Fund at im.bnymellon.com/literaturecenter. You can also request this information by calling 1-800-373-9387 (inside the U.S. only) or by sending an e-mail request to info@bnymellon.com. | |
| Additional Information Phone Number | 1-800-373-9387 | |
| Additional Information Email | info@bnymellon.com | |
| Additional Information Website | im.bnymellon.com/literaturecenter | |
| Expenses [Text Block] | What were the Fund’s costs for the last six months? (based on a hypothetical $10,000 investment) Share Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class I * $35 0.70% ** * During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. ** Annualized | |
| Expenses Paid, Amount | $ 35 | [5] |
| Expense Ratio, Percent | 0.70% | [5],[6] |
| Net Assets | $ 563,000,000 | |
| Holdings Count | 338 | |
| Portfolio Turnover | 57.20% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (AS OF 6/30/24) Fund Size (Millions) Number of Holdings Portfolio Turnover $563 338 57.20% | |
| Holdings [Text Block] | Portfolio Holdings (as of 6/30/24) Allocation of Holdings (Based on Net Assets) Sector Allocation (Based on Net Assets) | |
| Updated Prospectus Web Address | im.bnymellon.com/literaturecenter | |
| [1] During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. Annualized During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. Annualized During the period, fees were waived and/or expenses reimbursed pursuant to an agreement with the Fund’s investment adviser, BNY Mellon Investment Adviser, Inc. If this agreement is not extended in the future, expenses could be higher. Annualized | ||
| Shareholder Report, Holdings (Details) - BNY Mellon High Yield Fund | Jun. 30, 2024 |
| Class A - DQIAX | Net Other Assets and Liabilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (6.80%) |
| Class A - DQIAX | Collateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class A - DQIAX | Utilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| Class A - DQIAX | Technology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Class A - DQIAX | Basic Materials | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Class A - DQIAX | Energy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Class A - DQIAX | Communications | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Class A - DQIAX | Investment Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.80% |
| Class A - DQIAX | Financial | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Class A - DQIAX | Industrial | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Class A - DQIAX | Consumer, Cyclical | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.40% |
| Class A - DQIAX | Consumer, Non-cyclical | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.20% |
| Class A - DQIAX | Net Other Assets and Liabilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (6.70%) |
| Class A - DQIAX | Forward Foreign Currency Exchange Contracts | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0% |
| Class A - DQIAX | Exchange-Traded Funds | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class A - DQIAX | Collateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class A - DQIAX | Floating Rate Loan Interests | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Class A - DQIAX | Investment Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Class A - DQIAX | Corporate Bonds | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 85.80% |
| Class C - DQICX | Net Other Assets and Liabilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (6.80%) |
| Class C - DQICX | Collateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class C - DQICX | Utilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| Class C - DQICX | Technology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Class C - DQICX | Basic Materials | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Class C - DQICX | Energy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Class C - DQICX | Communications | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Class C - DQICX | Investment Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.80% |
| Class C - DQICX | Financial | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Class C - DQICX | Industrial | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Class C - DQICX | Consumer, Cyclical | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.40% |
| Class C - DQICX | Consumer, Non-cyclical | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.20% |
| Class C - DQICX | Net Other Assets and Liabilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (6.70%) |
| Class C - DQICX | Forward Foreign Currency Exchange Contracts | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0% |
| Class C - DQICX | Exchange-Traded Funds | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class C - DQICX | Collateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class C - DQICX | Floating Rate Loan Interests | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Class C - DQICX | Investment Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Class C - DQICX | Corporate Bonds | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 85.80% |
| Class I - DQIRX | Net Other Assets and Liabilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (6.80%) |
| Class I - DQIRX | Collateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class I - DQIRX | Utilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| Class I - DQIRX | Technology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Class I - DQIRX | Basic Materials | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Class I - DQIRX | Energy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Class I - DQIRX | Communications | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Class I - DQIRX | Investment Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.80% |
| Class I - DQIRX | Financial | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Class I - DQIRX | Industrial | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Class I - DQIRX | Consumer, Cyclical | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.40% |
| Class I - DQIRX | Consumer, Non-cyclical | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.20% |
| Class I - DQIRX | Net Other Assets and Liabilities | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | (6.70%) |
| Class I - DQIRX | Forward Foreign Currency Exchange Contracts | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0% |
| Class I - DQIRX | Exchange-Traded Funds | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class I - DQIRX | Collateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Class I - DQIRX | Floating Rate Loan Interests | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Class I - DQIRX | Investment Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Class I - DQIRX | Corporate Bonds | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 85.80% |
