| Form N-CSR Cover | 6 Months Ended |
| Jun. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | LOOMIS SAYLES FUNDS I |
| Entity Central Index Key | 0000917469 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
| Shareholder Report | 6 Months Ended |
| Jun. 30, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | LOOMIS SAYLES FUNDS I |
| Entity Central Index Key | 0000917469 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
| C000018124 | |
| Shareholder Report [Line Items] | |
| Fund Name | Loomis Sayles Bond Fund |
| Class Name | Admin Class |
| Trading Symbol | LBFAX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Loomis Sayles Bond Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information (including tax information) about the Fund at im.natixis.com/funddocuments This report describes changes to the Fund that occurred during the reporting period. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 800-225-5478 |
| Additional Information Website | im.natixis.com/funddocuments</span>" id="sjs-B20"><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;">im.natixis.com/funddocuments</span> |
| Expenses [Text Block] | What were the fund costs for the last six months? Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Admin Class $54 1.09% |
| Expenses Paid, Amount | $ 54 |
| Expense Ratio, Percent | 1.09% |
| AssetsNet | $ 4,356,767,123 |
| Holdings Count | Holding | 611 |
| Advisory Fees Paid, Amount | $ 11,111,452 |
| InvestmentCompanyPortfolioTurnover | 33% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $4,356,767,123 # of Portfolio Holdings (including overnight repurchase agreements and derivatives) 611 Portfolio Turnover Rate 33% Total Advisory Fees Paid $11,111,452 |
| Holdings [Text Block] | Industry Summary Value Value Other investments less than 3% of net assets Footnote Reference 30.3% Short-Term Investments 3.2% Pharmaceuticals 3.0% ABS Car Loan 3.2% Metals & Mining 3.2% Life Insurance 3.3% ABS Home Equity 4.2% Collateralized Loan Obligations 4.3% Banking 4.5% Sovereigns 4.6% ABS Other 5.0% Technology 5.0% Finance Companies 5.1% Cable Satellite 7.3% Treasuries 13.8% Footnote Description Footnote * Net of other assets less liabilities (including forward foreign currency and futures contracts) |
| Material Fund Change [Text Block] | Material Fund Changes Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments Expenses: |
| Material Fund Change Expenses [Text Block] | Expenses: |
| Summary of Change Legend [Text Block] | Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments |
| Updated Prospectus Phone Number | 800-225-5478 |
| Updated Prospectus Web Address | im.natixis.com/funddocuments</span>" id="sjs-B34"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">im.natixis.com/funddocuments</span> |
| C000125493 | |
| Shareholder Report [Line Items] | |
| Fund Name | Loomis Sayles Bond Fund |
| Class Name | Class N |
| Trading Symbol | LSBNX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Loomis Sayles Bond Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information (including tax information) about the Fund at im.natixis.com/funddocuments This report describes changes to the Fund that occurred during the reporting period. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 800-225-5478 |
| Additional Information Website | im.natixis.com/funddocuments</span>" id="sjs-B45"><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;">im.natixis.com/funddocuments</span> |
| Expenses [Text Block] | What were the fund costs for the last six months? Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class N $31 0.61% |
| Expenses Paid, Amount | $ 31 |
| Expense Ratio, Percent | 0.61% |
| AssetsNet | $ 4,356,767,123 |
| Holdings Count | Holding | 611 |
| Advisory Fees Paid, Amount | $ 11,111,452 |
| InvestmentCompanyPortfolioTurnover | 33% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $4,356,767,123 # of Portfolio Holdings (including overnight repurchase agreements and derivatives) 611 Portfolio Turnover Rate 33% Total Advisory Fees Paid $11,111,452 |
| Holdings [Text Block] | Industry Summary Value Value Other investments less than 3% of net assets Footnote Reference 30.3% Short-Term Investments 3.2% Pharmaceuticals 3.0% ABS Car Loan 3.2% Metals & Mining 3.2% Life Insurance 3.3% ABS Home Equity 4.2% Collateralized Loan Obligations 4.3% Banking 4.5% Sovereigns 4.6% ABS Other 5.0% Technology 5.0% Finance Companies 5.1% Cable Satellite 7.3% Treasuries 13.8% Footnote Description Footnote * Net of other assets less liabilities (including forward foreign currency and futures contracts) |
| Material Fund Change [Text Block] | Material Fund Changes Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments Expenses: |
| Material Fund Change Expenses [Text Block] | Expenses: |
| Summary of Change Legend [Text Block] | Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments |
| Updated Prospectus Phone Number | 800-225-5478 |
| Updated Prospectus Web Address | im.natixis.com/funddocuments</span>" id="sjs-B59"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">im.natixis.com/funddocuments</span> |
| C000018122 | |
| Shareholder Report [Line Items] | |
| Fund Name | Loomis Sayles Bond Fund |
| Class Name | Institutional Class |
| Trading Symbol | LSBDX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Loomis Sayles Bond Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information (including tax information) about the Fund at im.natixis.com/funddocuments This report describes changes to the Fund that occurred during the reporting period. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 800-225-5478 |
| Additional Information Website | im.natixis.com/funddocuments</span>" id="sjs-B70"><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;">im.natixis.com/funddocuments</span> |
| Expenses [Text Block] | What were the fund costs for the last six months? Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Institutional Class $33 0.66% |
| Expenses Paid, Amount | $ 33 |
| Expense Ratio, Percent | 0.66% |
| AssetsNet | $ 4,356,767,123 |
| Holdings Count | Holding | 611 |
| Advisory Fees Paid, Amount | $ 11,111,452 |
| InvestmentCompanyPortfolioTurnover | 33% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $4,356,767,123 # of Portfolio Holdings (including overnight repurchase agreements and derivatives) 611 Portfolio Turnover Rate 33% Total Advisory Fees Paid $11,111,452 |
| Holdings [Text Block] | Industry Summary Value Value Other investments less than 3% of net assets Footnote Reference 30.3% Short-Term Investments 3.2% Pharmaceuticals 3.0% ABS Car Loan 3.2% Metals & Mining 3.2% Life Insurance 3.3% ABS Home Equity 4.2% Collateralized Loan Obligations 4.3% Banking 4.5% Sovereigns 4.6% ABS Other 5.0% Technology 5.0% Finance Companies 5.1% Cable Satellite 7.3% Treasuries 13.8% Footnote Description Footnote * Net of other assets less liabilities (including forward foreign currency and futures contracts) |
| Material Fund Change [Text Block] | Material Fund Changes Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments Expenses: |
| Material Fund Change Expenses [Text Block] | Expenses: |
| Summary of Change Legend [Text Block] | Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments |
| Updated Prospectus Phone Number | 800-225-5478 |
| Updated Prospectus Web Address | im.natixis.com/funddocuments</span>" id="sjs-B84"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">im.natixis.com/funddocuments</span> |
| C000018123 | |
| Shareholder Report [Line Items] | |
| Fund Name | Loomis Sayles Bond Fund |
| Class Name | Retail Class |
| Trading Symbol | LSBRX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Loomis Sayles Bond Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information (including tax information) about the Fund at im.natixis.com/funddocuments This report describes changes to the Fund that occurred during the reporting period. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 800-225-5478 |
| Additional Information Website | im.natixis.com/funddocuments</span>" id="sjs-B95"><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;">im.natixis.com/funddocuments</span> |
| Expenses [Text Block] | What were the fund costs for the last six months? Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Retail Class $45 0.91% |
| Expenses Paid, Amount | $ 45 |
| Expense Ratio, Percent | 0.91% |
| AssetsNet | $ 4,356,767,123 |
| Holdings Count | Holding | 611 |
| Advisory Fees Paid, Amount | $ 11,111,452 |
| InvestmentCompanyPortfolioTurnover | 33% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $4,356,767,123 # of Portfolio Holdings (including overnight repurchase agreements and derivatives) 611 Portfolio Turnover Rate 33% Total Advisory Fees Paid $11,111,452 |
| Holdings [Text Block] | Industry Summary Value Value Other investments less than 3% of net assets Footnote Reference 30.3% Short-Term Investments 3.2% Pharmaceuticals 3.0% ABS Car Loan 3.2% Metals & Mining 3.2% Life Insurance 3.3% ABS Home Equity 4.2% Collateralized Loan Obligations 4.3% Banking 4.5% Sovereigns 4.6% ABS Other 5.0% Technology 5.0% Finance Companies 5.1% Cable Satellite 7.3% Treasuries 13.8% Footnote Description Footnote * Net of other assets less liabilities (including forward foreign currency and futures contracts) |
| Material Fund Change [Text Block] | Material Fund Changes Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments Expenses: |
| Material Fund Change Expenses [Text Block] | Expenses: |
| Summary of Change Legend [Text Block] | Effective July 1, 2024, the Fund had the following material changes, which were reported in a supplement to the Fund's prospectus. For more information, you may review the Fund's prospectus at im.natixis.com/funddocuments |
| Updated Prospectus Phone Number | 800-225-5478 |
| Updated Prospectus Web Address | im.natixis.com/funddocuments</span>" id="sjs-B109"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">im.natixis.com/funddocuments</span> |
| C000018133 | |
| Shareholder Report [Line Items] | |
| Fund Name | Loomis Sayles Investment Grade Fixed Income Fund |
| Class Name | Institutional Class |
| Trading Symbol | LSIGX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Loomis Sayles Investment Grade Fixed Income Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information (including tax information) about the Fund at im.natixis.com/funddocuments |
| Additional Information Phone Number | 800-225-5478 |
| Additional Information Website | im.natixis.com/funddocuments</span>" id="sjs-B119"><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;">im.natixis.com/funddocuments</span> |
| Expenses [Text Block] | What were the fund costs for the last six months? Class Name Cost of a $10,000 investment Costs paid as a percentage of a $10,000 investment Institutional Class $26 0.53% |
| Expenses Paid, Amount | $ 26 |
| Expense Ratio, Percent | 0.53% |
| AssetsNet | $ 206,243,272 |
| Holdings Count | Holding | 646 |
| Advisory Fees Paid, Amount | $ 353,027 |
| InvestmentCompanyPortfolioTurnover | 19% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $206,243,272 # of Portfolio Holdings (including overnight repurchase agreements and derivatives) 646 Portfolio Turnover Rate 19% Total Advisory Fees Paid $353,027 |
| Holdings [Text Block] | Industry Summary Value Value Other investments less than 3% of net assets Footnote Reference 32.8% Short-Term Investments 4.0% Metals & Mining 3.0% Collateralized Loan Obligations 3.2% Midstream 3.3% Sovereigns 3.5% Finance Companies 4.0% ABS Home Equity 4.5% ABS Other 4.5% ABS Car Loan 5.0% Technology 7.1% Banking 9.2% Treasuries 15.9% Footnote Description Footnote * Net of other assets less liabilities (including futures contracts) |
| Material Fund Change [Text Block] | Material Fund Changes There were no material fund changes during the period. |
| Updated Prospectus Phone Number | 800-225-5478 |
| Updated Prospectus Web Address | im.natixis.com/funddocuments</span>" id="sjs-B131"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">im.natixis.com/funddocuments</span> |
| Shareholder Report, Holdings (Details) | Jun. 30, 2024 |
| C000018124 | Cash & equivalents | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.60% |
| C000018124 | US Treasury | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.30% |
| C000018124 | Not rated | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.90% |
| C000018124 | CC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000018124 | CCC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| C000018124 | B | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| C000018124 | BB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.80% |
| C000018124 | BBB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 36% |
| C000018124 | A | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| C000018124 | AA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000018124 | AAA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| C000018124 | Sector Other Net Line | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 30.30% |
| C000018124 | SectorShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018124 | SectorPharmaceuticals | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| C000018124 | SectorABS Car Loan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018124 | SectorMetals & Mining | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018124 | SectorLife Insurance | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000018124 | SectorABS Home Equity | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| C000018124 | SectorCollateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| C000018124 | SectorBanking | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| C000018124 | SectorSovereigns | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| C000018124 | SectorABS Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000018124 | SectorTechnology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000018124 | SectorFinance Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000018124 | SectorCable Satellite | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.30% |
| C000018124 | SectorTreasuries | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.80% |
| C000125493 | Cash & equivalents | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.60% |
| C000125493 | US Treasury | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.30% |
| C000125493 | Not rated | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.90% |
| C000125493 | CC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000125493 | CCC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| C000125493 | B | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| C000125493 | BB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.80% |
| C000125493 | BBB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 36% |
| C000125493 | A | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| C000125493 | AA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000125493 | AAA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| C000125493 | Sector Other Net Line | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 30.30% |
| C000125493 | SectorShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000125493 | SectorPharmaceuticals | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| C000125493 | SectorABS Car Loan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000125493 | SectorMetals & Mining | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000125493 | SectorLife Insurance | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000125493 | SectorABS Home Equity | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| C000125493 | SectorCollateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| C000125493 | SectorBanking | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| C000125493 | SectorSovereigns | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| C000125493 | SectorABS Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000125493 | SectorTechnology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000125493 | SectorFinance Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000125493 | SectorCable Satellite | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.30% |
| C000125493 | SectorTreasuries | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.80% |
| C000018122 | Cash & equivalents | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.60% |
| C000018122 | US Treasury | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.30% |
| C000018122 | Not rated | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.90% |
| C000018122 | CC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000018122 | CCC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| C000018122 | B | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| C000018122 | BB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.80% |
| C000018122 | BBB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 36% |
| C000018122 | A | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| C000018122 | AA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000018122 | AAA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| C000018122 | Sector Other Net Line | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 30.30% |
| C000018122 | SectorShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018122 | SectorPharmaceuticals | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| C000018122 | SectorABS Car Loan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018122 | SectorMetals & Mining | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018122 | SectorLife Insurance | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000018122 | SectorABS Home Equity | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| C000018122 | SectorCollateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| C000018122 | SectorBanking | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| C000018122 | SectorSovereigns | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| C000018122 | SectorABS Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000018122 | SectorTechnology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000018122 | SectorFinance Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000018122 | SectorCable Satellite | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.30% |
| C000018122 | SectorTreasuries | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.80% |
| C000018123 | Cash & equivalents | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.60% |
| C000018123 | US Treasury | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.30% |
| C000018123 | Not rated | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.90% |
| C000018123 | CC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000018123 | CCC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| C000018123 | B | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| C000018123 | BB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.80% |
| C000018123 | BBB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 36% |
| C000018123 | A | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| C000018123 | AA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000018123 | AAA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| C000018123 | Sector Other Net Line | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 30.30% |
| C000018123 | SectorShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018123 | SectorPharmaceuticals | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| C000018123 | SectorABS Car Loan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018123 | SectorMetals & Mining | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018123 | SectorLife Insurance | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| C000018123 | SectorABS Home Equity | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| C000018123 | SectorCollateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| C000018123 | SectorBanking | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| C000018123 | SectorSovereigns | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| C000018123 | SectorABS Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000018123 | SectorTechnology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000018123 | SectorFinance Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| C000018123 | SectorCable Satellite | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.30% |
| C000018123 | SectorTreasuries | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.80% |
| C000018133 | Cash & equivalents | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| C000018133 | US Treasury | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| C000018133 | Not rated | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.10% |
| C000018133 | CC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| C000018133 | CCC | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.60% |
| C000018133 | B | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| C000018133 | BB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.40% |
| C000018133 | BBB | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 47.20% |
| C000018133 | A | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.10% |
| C000018133 | AA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| C000018133 | AAA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.50% |
| C000018133 | Sector Other Net Line | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.80% |
| C000018133 | SectorShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| C000018133 | SectorABS Car Loan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| C000018133 | SectorMetals & Mining | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| C000018133 | SectorABS Home Equity | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| C000018133 | SectorCollateralized Loan Obligations | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| C000018133 | SectorBanking | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.20% |
| C000018133 | SectorSovereigns | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.50% |
| C000018133 | SectorABS Other | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| C000018133 | SectorTechnology | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.10% |
| C000018133 | SectorFinance Companies | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| C000018133 | SectorTreasuries | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.90% |
| C000018133 | SectorMidstream | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
