Shareholder Report, Holdings (Details)	Nov. 30, 2025
C000024768 | Common Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[1]
C000024768 | Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[1]
C000024768 | Preferred Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[1]
C000024768 | Short-Term Municipals
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[1]
C000024768 | Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000024768 | Corporate Debt Securities
Holdings [Line Items]
Percent of Net Asset Value	98.50%
C000024770 | Common Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[2]
C000024770 | Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[2]
C000024770 | Preferred Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[2]
C000024770 | Short-Term Municipals
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[2]
C000024770 | Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000024770 | Corporate Debt Securities
Holdings [Line Items]
Percent of Net Asset Value	98.50%
C000024771 | Common Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[3]
C000024771 | Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[3]
C000024771 | Preferred Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[3]
C000024771 | Short-Term Municipals
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[3]
C000024771 | Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000024771 | Corporate Debt Securities
Holdings [Line Items]
Percent of Net Asset Value	98.50%
C000062220 | Common Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[4]
C000062220 | Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[4]
C000062220 | Preferred Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[4]
C000062220 | Short-Term Municipals
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[4]
C000062220 | Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000062220 | Corporate Debt Securities
Holdings [Line Items]
Percent of Net Asset Value	98.50%
C000173769 | Common Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[5]
C000173769 | Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[5]
C000173769 | Preferred Stock
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[5]
C000173769 | Short-Term Municipals
Holdings [Line Items]
Percent of Net Asset Value	0.00%	[5]
C000173769 | Cash Equivalents
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000173769 | Corporate Debt Securities
Holdings [Line Items]
Percent of Net Asset Value	98.50%

[1] Represents less than 0.1%.

[2] Represents less than 0.1%.

[3] Represents less than 0.1%.

[4] Represents less than 0.1%.

[5] Represents less than 0.1%.