v3.25.2
Shareholder Report, Holdings (Details)
Apr. 30, 2025
C000006295 | Cash and Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value (3.10%)
C000006295 | Not Rated  
Holdings [Line Items]  
Percent of Net Asset Value 24.50%
C000006295 | CCC  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
C000006295 | B  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
C000006295 | BB  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
C000006295 | BBB  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000006295 | A  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
C000006295 | AA  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
C000006295 | AAA  
Holdings [Line Items]  
Percent of Net Asset Value 21.00%
C000006295 | AssetSenior Loan Interests  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000006295 | AssetCollateralized Mortgage Obligations - Agency Collateral Series  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000006295 | AssetSupranational  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000006295 | AssetInvestment Companies  
Holdings [Line Items]  
Percent of Total Investments 0.80%
C000006295 | AssetCommercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000006295 | AssetAgency Fixed Rate Mortgages  
Holdings [Line Items]  
Percent of Total Investments 7.50%
C000006295 | AssetSovereign  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000006295 | AssetAsset-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 12.00%
C000006295 | AssetShort-Term Investments  
Holdings [Line Items]  
Percent of Total Investments 12.90%
C000006295 | AssetMortgages - Other  
Holdings [Line Items]  
Percent of Total Investments 19.90%
C000006295 | AssetCorporate Bonds  
Holdings [Line Items]  
Percent of Total Investments 32.80%
C000155980 | Cash and Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value (3.10%)
C000155980 | Not Rated  
Holdings [Line Items]  
Percent of Net Asset Value 24.50%
C000155980 | CCC  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
C000155980 | B  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
C000155980 | BB  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
C000155980 | BBB  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000155980 | A  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
C000155980 | AA  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
C000155980 | AAA  
Holdings [Line Items]  
Percent of Net Asset Value 21.00%
C000155980 | AssetSenior Loan Interests  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000155980 | AssetCollateralized Mortgage Obligations - Agency Collateral Series  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000155980 | AssetSupranational  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000155980 | AssetInvestment Companies  
Holdings [Line Items]  
Percent of Total Investments 0.80%
C000155980 | AssetCommercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000155980 | AssetAgency Fixed Rate Mortgages  
Holdings [Line Items]  
Percent of Total Investments 7.50%
C000155980 | AssetSovereign  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000155980 | AssetAsset-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 12.00%
C000155980 | AssetShort-Term Investments  
Holdings [Line Items]  
Percent of Total Investments 12.90%
C000155980 | AssetMortgages - Other  
Holdings [Line Items]  
Percent of Total Investments 19.90%
C000155980 | AssetCorporate Bonds  
Holdings [Line Items]  
Percent of Total Investments 32.80%
C000006298 | Cash and Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value (3.10%)
C000006298 | Not Rated  
Holdings [Line Items]  
Percent of Net Asset Value 24.50%
C000006298 | CCC  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
C000006298 | B  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
C000006298 | BB  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
C000006298 | BBB  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000006298 | A  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
C000006298 | AA  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
C000006298 | AAA  
Holdings [Line Items]  
Percent of Net Asset Value 21.00%
C000006298 | AssetSenior Loan Interests  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000006298 | AssetCollateralized Mortgage Obligations - Agency Collateral Series  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000006298 | AssetSupranational  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000006298 | AssetInvestment Companies  
Holdings [Line Items]  
Percent of Total Investments 0.80%
C000006298 | AssetCommercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000006298 | AssetAgency Fixed Rate Mortgages  
Holdings [Line Items]  
Percent of Total Investments 7.50%
C000006298 | AssetSovereign  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000006298 | AssetAsset-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 12.00%
C000006298 | AssetShort-Term Investments  
Holdings [Line Items]  
Percent of Total Investments 12.90%
C000006298 | AssetMortgages - Other  
Holdings [Line Items]  
Percent of Total Investments 19.90%
C000006298 | AssetCorporate Bonds  
Holdings [Line Items]  
Percent of Total Investments 32.80%
C000198830 | Cash and Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value (3.10%)
C000198830 | Not Rated  
Holdings [Line Items]  
Percent of Net Asset Value 24.50%
C000198830 | CCC  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
C000198830 | B  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
C000198830 | BB  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
C000198830 | BBB  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000198830 | A  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
C000198830 | AA  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
C000198830 | AAA  
Holdings [Line Items]  
Percent of Net Asset Value 21.00%
C000198830 | AssetSenior Loan Interests  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000198830 | AssetCollateralized Mortgage Obligations - Agency Collateral Series  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000198830 | AssetSupranational  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000198830 | AssetInvestment Companies  
Holdings [Line Items]  
Percent of Total Investments 0.80%
C000198830 | AssetCommercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000198830 | AssetAgency Fixed Rate Mortgages  
Holdings [Line Items]  
Percent of Total Investments 7.50%
C000198830 | AssetSovereign  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000198830 | AssetAsset-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 12.00%
C000198830 | AssetShort-Term Investments  
Holdings [Line Items]  
Percent of Total Investments 12.90%
C000198830 | AssetMortgages - Other  
Holdings [Line Items]  
Percent of Total Investments 19.90%
C000198830 | AssetCorporate Bonds  
Holdings [Line Items]  
Percent of Total Investments 32.80%
C000006297 | Cash and Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value (3.10%)
C000006297 | Not Rated  
Holdings [Line Items]  
Percent of Net Asset Value 24.50%
C000006297 | CCC  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
C000006297 | B  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
C000006297 | BB  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
C000006297 | BBB  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000006297 | A  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
C000006297 | AA  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
C000006297 | AAA  
Holdings [Line Items]  
Percent of Net Asset Value 21.00%
C000006297 | AssetSenior Loan Interests  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000006297 | AssetCollateralized Mortgage Obligations - Agency Collateral Series  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000006297 | AssetSupranational  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000006297 | AssetInvestment Companies  
Holdings [Line Items]  
Percent of Total Investments 0.80%
C000006297 | AssetCommercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000006297 | AssetAgency Fixed Rate Mortgages  
Holdings [Line Items]  
Percent of Total Investments 7.50%
C000006297 | AssetSovereign  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000006297 | AssetAsset-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 12.00%
C000006297 | AssetShort-Term Investments  
Holdings [Line Items]  
Percent of Total Investments 12.90%
C000006297 | AssetMortgages - Other  
Holdings [Line Items]  
Percent of Total Investments 19.90%
C000006297 | AssetCorporate Bonds  
Holdings [Line Items]  
Percent of Total Investments 32.80%
C000126926 | Cash and Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value (3.10%)
C000126926 | Not Rated  
Holdings [Line Items]  
Percent of Net Asset Value 24.50%
C000126926 | CCC  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
C000126926 | B  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
C000126926 | BB  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
C000126926 | BBB  
Holdings [Line Items]  
Percent of Net Asset Value 27.20%
C000126926 | A  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
C000126926 | AA  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
C000126926 | AAA  
Holdings [Line Items]  
Percent of Net Asset Value 21.00%
C000126926 | AssetSenior Loan Interests  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000126926 | AssetCollateralized Mortgage Obligations - Agency Collateral Series  
Holdings [Line Items]  
Percent of Total Investments 0.30%
C000126926 | AssetSupranational  
Holdings [Line Items]  
Percent of Total Investments 0.60%
C000126926 | AssetInvestment Companies  
Holdings [Line Items]  
Percent of Total Investments 0.80%
C000126926 | AssetCommercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 3.70%
C000126926 | AssetAgency Fixed Rate Mortgages  
Holdings [Line Items]  
Percent of Total Investments 7.50%
C000126926 | AssetSovereign  
Holdings [Line Items]  
Percent of Total Investments 9.20%
C000126926 | AssetAsset-Backed Securities  
Holdings [Line Items]  
Percent of Total Investments 12.00%
C000126926 | AssetShort-Term Investments  
Holdings [Line Items]  
Percent of Total Investments 12.90%
C000126926 | AssetMortgages - Other  
Holdings [Line Items]  
Percent of Total Investments 19.90%
C000126926 | AssetCorporate Bonds  
Holdings [Line Items]  
Percent of Total Investments 32.80%