S000010032 [Member] Investment Objectives and Goals - The National Tax-Free Intermediate Bond Fund |
Oct. 31, 2025 |
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| Prospectus [Line Items] | |
| Risk/Return [Heading] | The National Tax‑Free Intermediate Bond Fund – Summary |
| Objective [Heading] | Investment Objective |
| Objective, Primary [Text Block] | The investment objective of the Fund is to seek current income exempt from federal income tax as is consistent with the preservation of capital.
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