| Shareholder Report | 6 Months Ended |
| May 31, 2024 USD ($) Holding |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Federated Hermes Investment Series Funds, Inc. |
| Entity Central Index Key | 0000889388 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | May 31, 2024 |
| C000173769 | |
| Shareholder Report [Line Items] | |
| Fund Name | Federated Hermes Corporate Bond Fund |
| Class Name | R6 Shares |
| Trading Symbol | FDBLX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Federated Hermes Corporate Bond Fund (the "Fund") for the period of December 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information at www.FederatedHermes.com/us/FundInformation |
| Additional Information Phone Number | 1-800-341-7400 |
| Additional Information Website | <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span>" id="sjs-B19"><span style="text-decoration: underline solid rgb(0, 0, 0); box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; height: auto; max-height: none; min-height: 0px;"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class R6 Shares $29 0.58% |
| Expenses Paid, Amount | $ 29 |
| Expense Ratio, Percent | 0.58% |
| AssetsNet | $ 1,124,911,180 |
| Holdings Count | Holding | 415 |
| InvestmentCompanyPortfolioTurnover | 5% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Net Assets $1,124,911,180 Number of Investments 415 Portfolio Turnover 5% |
| Holdings [Text Block] | Top Security Types (% of Net Assets) Value Value Other Security Types Footnote Reference 0.0% Footnote Reference Collateralized Mortgage Obligations Footnote Reference 0.0% Footnote Reference Mortgage Backed Securities Footnote Reference 0.0% Footnote Reference Municipal Bond 0.1% U.S. Treasury Securities 3.8% Cash Equivalents 4.5% High Yield Bond Core Fund 8.2% Corporate Debt Securities 82.5% Footnote Description Footnote * Represents less than 0.1%. |
| Material Fund Change [Text Block] | |
| C000024768 | |
| Shareholder Report [Line Items] | |
| Fund Name | Federated Hermes Corporate Bond Fund |
| Class Name | Class A |
| Trading Symbol | FDBAX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Federated Hermes Corporate Bond Fund (the "Fund") for the period of December 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information at www.FederatedHermes.com/us/FundInformation |
| Additional Information Phone Number | 1-800-341-7400 |
| Additional Information Website | <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span>" id="sjs-B38"><span style="text-decoration: underline solid rgb(0, 0, 0); box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; height: auto; max-height: none; min-height: 0px;"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class A Shares $43 0.85% |
| Expenses Paid, Amount | $ 43 |
| Expense Ratio, Percent | 0.85% |
| AssetsNet | $ 1,124,911,180 |
| Holdings Count | Holding | 415 |
| InvestmentCompanyPortfolioTurnover | 5% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Net Assets $1,124,911,180 Number of Investments 415 Portfolio Turnover 5% |
| Holdings [Text Block] | Top Security Types (% of Net Assets) Value Value Other Security Types Footnote Reference 0.0% Footnote Reference Collateralized Mortgage Obligations Footnote Reference 0.0% Footnote Reference Mortgage Backed Securities Footnote Reference 0.0% Footnote Reference Municipal Bond 0.1% U.S. Treasury Securities 3.8% Cash Equivalents 4.5% High Yield Bond Core Fund 8.2% Corporate Debt Securities 82.5% Footnote Description Footnote * Represents less than 0.1%. |
| Material Fund Change [Text Block] | |
| C000024770 | |
| Shareholder Report [Line Items] | |
| Fund Name | Federated Hermes Corporate Bond Fund |
| Class Name | Class C |
| Trading Symbol | FDBCX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Federated Hermes Corporate Bond Fund (the "Fund") for the period of December 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information at www.FederatedHermes.com/us/FundInformation |
| Additional Information Phone Number | 1-800-341-7400 |
| Additional Information Website | <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span>" id="sjs-B57"><span style="text-decoration: underline solid rgb(0, 0, 0); box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; height: auto; max-height: none; min-height: 0px;"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class C Shares $85 1.68% |
| Expenses Paid, Amount | $ 85 |
| Expense Ratio, Percent | 1.68% |
| AssetsNet | $ 1,124,911,180 |
| Holdings Count | Holding | 415 |
| InvestmentCompanyPortfolioTurnover | 5% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Net Assets $1,124,911,180 Number of Investments 415 Portfolio Turnover 5% |
| Holdings [Text Block] | Top Security Types (% of Net Assets) Value Value Other Security Types Footnote Reference 0.0% Footnote Reference Collateralized Mortgage Obligations Footnote Reference 0.0% Footnote Reference Mortgage Backed Securities Footnote Reference 0.0% Footnote Reference Municipal Bond 0.1% U.S. Treasury Securities 3.8% Cash Equivalents 4.5% High Yield Bond Core Fund 8.2% Corporate Debt Securities 82.5% Footnote Description Footnote * Represents less than 0.1%. |
| Material Fund Change [Text Block] | |
| C000024771 | |
| Shareholder Report [Line Items] | |
| Fund Name | Federated Hermes Corporate Bond Fund |
| Class Name | Class F |
| Trading Symbol | ISHIX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Federated Hermes Corporate Bond Fund (the "Fund") for the period of December 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information at www.FederatedHermes.com/us/FundInformation |
| Additional Information Phone Number | 1-800-341-7400 |
| Additional Information Website | <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span>" id="sjs-B76"><span style="text-decoration: underline solid rgb(0, 0, 0); box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; height: auto; max-height: none; min-height: 0px;"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class F Shares $43 0.85% |
| Expenses Paid, Amount | $ 43 |
| Expense Ratio, Percent | 0.85% |
| AssetsNet | $ 1,124,911,180 |
| Holdings Count | Holding | 415 |
| InvestmentCompanyPortfolioTurnover | 5% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Net Assets $1,124,911,180 Number of Investments 415 Portfolio Turnover 5% |
| Holdings [Text Block] | Top Security Types (% of Net Assets) Value Value Other Security Types Footnote Reference 0.0% Footnote Reference Collateralized Mortgage Obligations Footnote Reference 0.0% Footnote Reference Mortgage Backed Securities Footnote Reference 0.0% Footnote Reference Municipal Bond 0.1% U.S. Treasury Securities 3.8% Cash Equivalents 4.5% High Yield Bond Core Fund 8.2% Corporate Debt Securities 82.5% Footnote Description Footnote * Represents less than 0.1%. |
| Material Fund Change [Text Block] | |
| C000062220 | |
| Shareholder Report [Line Items] | |
| Fund Name | Federated Hermes Corporate Bond Fund |
| Class Name | Institutional Shares |
| Trading Symbol | FDBIX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Federated Hermes Corporate Bond Fund (the "Fund") for the period of December 1, 2023 to May 31, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information at www.FederatedHermes.com/us/FundInformation |
| Additional Information Phone Number | 1-800-341-7400 |
| Additional Information Website | <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span>" id="sjs-B95"><span style="text-decoration: underline solid rgb(0, 0, 0); box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; height: auto; max-height: none; min-height: 0px;"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 12px; font-weight: 400; grid-area: auto; line-height: 18px; margin: 0px; overflow: visible; text-align: left; text-decoration: underline solid rgb(0, 0, 0); height: auto; max-height: none; min-height: 0px;">www.FederatedHermes.com/us/FundInformation</span></span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? (based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Institutional Shares $30 0.60% |
| Expenses Paid, Amount | $ 30 |
| Expense Ratio, Percent | 0.60% |
| AssetsNet | $ 1,124,911,180 |
| Holdings Count | Holding | 415 |
| InvestmentCompanyPortfolioTurnover | 5% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Net Assets $1,124,911,180 Number of Investments 415 Portfolio Turnover 5% |
| Holdings [Text Block] | Top Security Types (% of Net Assets) Value Value Other Security Types Footnote Reference 0.0% Footnote Reference Collateralized Mortgage Obligations Footnote Reference 0.0% Footnote Reference Mortgage Backed Securities Footnote Reference 0.0% Footnote Reference Municipal Bond 0.1% U.S. Treasury Securities 3.8% Cash Equivalents 4.5% High Yield Bond Core Fund 8.2% Corporate Debt Securities 82.5% Footnote Description Footnote * Represents less than 0.1%. |
| Material Fund Change [Text Block] | |
