Shareholder Report, Holdings (Details)	Jul. 31, 2025
C000024572 \| Greater than 5 Years
Holdings [Line Items]
Percent of Net Asset Value	9.90%
C000024572 \| 2-5 Years
Holdings [Line Items]
Percent of Net Asset Value	73.50%
C000024572 \| Less than 2 Years
Holdings [Line Items]
Percent of Net Asset Value	14.60%
C000024572 \| Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	1.30%
C000024572 \| Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	6.40%
C000024572 \| Collaterized Mortgage Obligations
Holdings [Line Items]
Percent of Net Asset Value	14.40%
C000024572 \| U.S. Treasury Securities
Holdings [Line Items]
Percent of Net Asset Value	77.20%
C000024571 \| Greater than 5 Years
Holdings [Line Items]
Percent of Net Asset Value	9.90%
C000024571 \| 2-5 Years
Holdings [Line Items]
Percent of Net Asset Value	73.50%
C000024571 \| Less than 2 Years
Holdings [Line Items]
Percent of Net Asset Value	14.60%
C000024571 \| Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	1.30%
C000024571 \| Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	6.40%
C000024571 \| Collaterized Mortgage Obligations
Holdings [Line Items]
Percent of Net Asset Value	14.40%
C000024571 \| U.S. Treasury Securities
Holdings [Line Items]
Percent of Net Asset Value	77.20%
C000024573 \| Greater than 5 Years
Holdings [Line Items]
Percent of Net Asset Value	9.90%
C000024573 \| 2-5 Years
Holdings [Line Items]
Percent of Net Asset Value	73.50%
C000024573 \| Less than 2 Years
Holdings [Line Items]
Percent of Net Asset Value	14.60%
C000024573 \| Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	1.30%
C000024573 \| Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	6.40%
C000024573 \| Collaterized Mortgage Obligations
Holdings [Line Items]
Percent of Net Asset Value	14.40%
C000024573 \| U.S. Treasury Securities
Holdings [Line Items]
Percent of Net Asset Value	77.20%