v3.25.1
Shareholder Report, Holdings (Details)
Feb. 28, 2025
C000005557 | Virginia Housing Dev. Auth., Tender Option Bond Trust Receipts  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
C000005557 | Roanoke Economic Dev. Auth., Carilion Clinic Obligated  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
C000005557 | Clark County Dept. of Aviation  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000005557 | New York City Transational Fin. Auth., Tender Option Bond Trust Receipts  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000005557 | Rhode Island Health & Ed. Building  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000005557 | Missouri HEFA, SSM Health Care  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000005557 | Houston Combined Utility System  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000005557 | Harris County  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000005557 | Greenville County School Dist.  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
C000005557 | South Carolina Public Service Auth.  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
C000005557 | Other Holdings Grouping  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
C000005557 | Other Municipal Security  
Holdings [Line Items]  
Percent of Net Asset Value 43.40%
C000005557 | Variable Rate Demand Notes  
Holdings [Line Items]  
Percent of Net Asset Value 33.60%
C000005557 | Non-Financial Company Commercial Paper  
Holdings [Line Items]  
Percent of Net Asset Value 21.60%
C000193189 | Virginia Housing Dev. Auth., Tender Option Bond Trust Receipts  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
C000193189 | Roanoke Economic Dev. Auth., Carilion Clinic Obligated  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
C000193189 | Clark County Dept. of Aviation  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000193189 | New York City Transational Fin. Auth., Tender Option Bond Trust Receipts  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000193189 | Rhode Island Health & Ed. Building  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000193189 | Missouri HEFA, SSM Health Care  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000193189 | Houston Combined Utility System  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000193189 | Harris County  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
C000193189 | Greenville County School Dist.  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
C000193189 | South Carolina Public Service Auth.  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
C000193189 | Other Holdings Grouping  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
C000193189 | Other Municipal Security  
Holdings [Line Items]  
Percent of Net Asset Value 43.40%
C000193189 | Variable Rate Demand Notes  
Holdings [Line Items]  
Percent of Net Asset Value 33.60%
C000193189 | Non-Financial Company Commercial Paper  
Holdings [Line Items]  
Percent of Net Asset Value 21.60%