v3.26.3
Load [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Bloomberg U.S. Intermediate Government Bond Index (Index reflects no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 6.50% 0.64% 1.75%
Bloomberg US Aggregate Index (Index reflects no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 7.30% (0.36%) 2.01%
Intermediate Government Bond Series      
Prospectus [Line Items]      
Average Annual Return, Percent 5.04% 1.59% 1.99%
Intermediate Government Bond Series | After Taxes on Distributions      
Prospectus [Line Items]      
Average Annual Return, Percent 3.57% 0.38% 0.86%
Intermediate Government Bond Series | After Taxes on Distributions and Sales      
Prospectus [Line Items]      
Average Annual Return, Percent [2] 2.96% 0.69% 1.02%
[1] The Bloomberg US Aggregate Index is presented solely to satisfy the regulatory requirement for a broad-based securities market index. The Bloomberg U.S. Intermediate Government Bond Index more accurately reflects the investment style and strategy of the Fund.
[2] Return after Taxes on Distributions & Sale of Fund Shares also includes any taxable gain or loss realized by a shareholder on the sale of a fund’s shares.