v3.26.1
Shareholder Report, Holdings (Details)
May 31, 2026
C000030200 | Commercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030200 | Foreign Governments/Agencies  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030200 | Cash Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
C000030200 | Emerging Markets Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
C000030200 | High Yield Bond Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
C000030200 | Project and Trade Finance Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030200 | Collaterized Mortgage Obligations  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030200 | Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
C000030200 | Corporate Bonds  
Holdings [Line Items]  
Percent of Net Asset Value 26.60%
C000030200 | U.S. Treasuries  
Holdings [Line Items]  
Percent of Net Asset Value 29.00%
C000030202 | Commercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030202 | Foreign Governments/Agencies  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030202 | Cash Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
C000030202 | Emerging Markets Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
C000030202 | High Yield Bond Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
C000030202 | Project and Trade Finance Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030202 | Collaterized Mortgage Obligations  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030202 | Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
C000030202 | Corporate Bonds  
Holdings [Line Items]  
Percent of Net Asset Value 26.60%
C000030202 | U.S. Treasuries  
Holdings [Line Items]  
Percent of Net Asset Value 29.00%
C000030204 | Commercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030204 | Foreign Governments/Agencies  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030204 | Cash Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
C000030204 | Emerging Markets Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
C000030204 | High Yield Bond Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
C000030204 | Project and Trade Finance Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030204 | Collaterized Mortgage Obligations  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030204 | Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
C000030204 | Corporate Bonds  
Holdings [Line Items]  
Percent of Net Asset Value 26.60%
C000030204 | U.S. Treasuries  
Holdings [Line Items]  
Percent of Net Asset Value 29.00%
C000030203 | Commercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030203 | Foreign Governments/Agencies  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030203 | Cash Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
C000030203 | Emerging Markets Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
C000030203 | High Yield Bond Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
C000030203 | Project and Trade Finance Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030203 | Collaterized Mortgage Obligations  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030203 | Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
C000030203 | Corporate Bonds  
Holdings [Line Items]  
Percent of Net Asset Value 26.60%
C000030203 | U.S. Treasuries  
Holdings [Line Items]  
Percent of Net Asset Value 29.00%
C000157740 | Commercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000157740 | Foreign Governments/Agencies  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000157740 | Cash Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
C000157740 | Emerging Markets Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
C000157740 | High Yield Bond Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
C000157740 | Project and Trade Finance Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000157740 | Collaterized Mortgage Obligations  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000157740 | Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
C000157740 | Corporate Bonds  
Holdings [Line Items]  
Percent of Net Asset Value 26.60%
C000157740 | U.S. Treasuries  
Holdings [Line Items]  
Percent of Net Asset Value 29.00%
C000030199 | Commercial Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030199 | Foreign Governments/Agencies  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
C000030199 | Cash Equivalents  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
C000030199 | Emerging Markets Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
C000030199 | High Yield Bond Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
C000030199 | Project and Trade Finance Core Fund  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030199 | Collaterized Mortgage Obligations  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
C000030199 | Mortgage-Backed Securities  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
C000030199 | Corporate Bonds  
Holdings [Line Items]  
Percent of Net Asset Value 26.60%
C000030199 | U.S. Treasuries  
Holdings [Line Items]  
Percent of Net Asset Value 29.00%