Shareholder Report, Holdings (Details)	Jan. 31, 2025
C000007089 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000007089 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	3.60%
C000007089 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	13.20%
C000007089 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	80.90%
C000007089 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.60%
C000007090 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	0.70%
C000007090 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	3.60%
C000007090 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	13.20%
C000007090 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	80.90%
C000007090 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.60%
C000007092 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000007092 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	12.90%
C000007092 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	15.30%
C000007092 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	3.40%
C000007092 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	10.50%
C000007092 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	9.50%
C000007092 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000007092 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	8.30%
C000007092 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	9.50%
C000007092 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	1.50%
C000007092 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	6.60%
C000007092 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	1.90%
C000007092 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	8.60%
C000007093 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000007093 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	12.90%
C000007093 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	15.30%
C000007093 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	3.40%
C000007093 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	10.50%
C000007093 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	9.50%
C000007093 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000007093 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	8.30%
C000007093 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	9.50%
C000007093 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	1.50%
C000007093 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	6.60%
C000007093 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	1.90%
C000007093 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	8.60%
C000007097 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.40%
C000007097 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	5.20%
C000007097 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	3.40%
C000007097 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	4.40%
C000007097 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	6.80%
C000007097 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	32.00%
C000007097 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	8.20%
C000007097 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000007097 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	2.30%
C000007097 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	4.30%
C000007097 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	4.40%
C000007097 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000007097 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	16.30%
C000007098 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.40%
C000007098 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	5.20%
C000007098 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	3.40%
C000007098 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	4.40%
C000007098 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	6.80%
C000007098 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	32.00%
C000007098 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	8.20%
C000007098 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	4.60%
C000007098 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	2.30%
C000007098 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	4.30%
C000007098 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	4.40%
C000007098 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	6.70%
C000007098 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	16.30%
C000007099 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	4.80%
C000007099 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000007099 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	6.30%
C000007099 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	82.80%
C000007099 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.70%
C000007099 \| Nonconventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	3.90%
C000007100 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	4.80%
C000007100 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000007100 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	6.30%
C000007100 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	82.80%
C000007100 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.70%
C000007100 \| Nonconventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	3.90%
C000007101 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	5.40%
C000007101 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	4.80%
C000007101 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	4.00%
C000007101 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000007101 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	6.10%
C000007101 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	16.80%
C000007101 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	12.20%
C000007101 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000007101 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000007101 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000007101 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	7.50%
C000007101 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	13.80%
C000007101 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	17.30%
C000007102 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	5.40%
C000007102 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	4.80%
C000007102 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	4.00%
C000007102 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000007102 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	6.10%
C000007102 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	16.80%
C000007102 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	12.20%
C000007102 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	5.30%
C000007102 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000007102 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	0.50%
C000007102 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	7.50%
C000007102 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	13.80%
C000007102 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	17.30%
C000007103 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	6.20%
C000007103 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	1.70%
C000007103 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	88.50%
C000007103 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.50%
C000007103 \| Nonconventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	2.10%
C000007104 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	6.20%
C000007104 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	1.70%
C000007104 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	88.50%
C000007104 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.50%
C000007104 \| Nonconventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	2.10%
C000007105 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	35.70%
C000007105 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	12.80%
C000007105 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	38.40%
C000007105 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	12.70%
C000007105 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	(3.30%)
C000007105 \| Nonconventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	3.70%
C000007106 \| Agency Bonds and Notes
Holdings [Line Items]
Percent of Net Asset Value	35.70%
C000007106 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	12.80%
C000007106 \| Conventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	38.40%
C000007106 \| U.S. Government Securities
Holdings [Line Items]
Percent of Net Asset Value	12.70%
C000007106 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	(3.30%)
C000007106 \| Nonconventional Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	3.70%
C000007107 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.40%
C000007107 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000007107 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000007107 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	4.50%
C000007107 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	6.40%
C000007107 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	30.30%
C000007107 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000007107 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	5.40%
C000007107 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	2.00%
C000007107 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	4.00%
C000007107 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000007107 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	5.70%
C000007107 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	17.50%
C000007108 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.40%
C000007108 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000007108 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000007108 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	4.50%
C000007108 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	6.40%
C000007108 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	30.30%
C000007108 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000007108 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	5.40%
C000007108 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	2.00%
C000007108 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	4.00%
C000007108 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000007108 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	5.70%
C000007108 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	17.50%
C000007109 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	1.40%
C000007109 \| Communications
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000007109 \| Consumer Discretionary
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000007109 \| Consumer Staples
Holdings [Line Items]
Percent of Net Asset Value	4.50%
C000007109 \| Energy
Holdings [Line Items]
Percent of Net Asset Value	6.40%
C000007109 \| Financials
Holdings [Line Items]
Percent of Net Asset Value	30.30%
C000007109 \| Health Care
Holdings [Line Items]
Percent of Net Asset Value	7.60%
C000007109 \| Industrials
Holdings [Line Items]
Percent of Net Asset Value	5.40%
C000007109 \| Materials
Holdings [Line Items]
Percent of Net Asset Value	2.00%
C000007109 \| Real Estate
Holdings [Line Items]
Percent of Net Asset Value	4.00%
C000007109 \| Technology
Holdings [Line Items]
Percent of Net Asset Value	5.10%
C000007109 \| Utilities
Holdings [Line Items]
Percent of Net Asset Value	5.70%
C000007109 \| Asset Other Line
Holdings [Line Items]
Percent of Net Asset Value	17.50%
C000151976 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]
Percent of Net Asset Value	25.60%
C000151976 \| Other Assets and Liabilities, Net
Holdings [Line Items]
Percent of Net Asset Value	5.50%
C000151976 \| Corporate Bonds
Holdings [Line Items]
Percent of Net Asset Value	63.90%
C000151976 \| Sovereign Bonds
Holdings [Line Items]
Percent of Net Asset Value	1.90%
C000151976 \| U.S. Government and Agency Obligations
Holdings [Line Items]
Percent of Net Asset Value	3.10%
C000151975 \| Asset-Backed/Commercial Mortgage-Backed Securities
Holdings [Line Items]

Shareholder Report, Holdings (Details)

Jan. 31, 2025