01001 - Document - Document and Entity Information {Elements}
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01002 - Document - Risk/Return Summary (Kansas Municipal Fund) {Unlabeled}
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01003 - Schedule - Shareholder Fees
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01004 - Schedule - Annual Fund Operating Expenses
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01005 - Schedule - Expense Example {Transposed}
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01006 - Schedule - Bar Chart [Table]
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01007 - Schedule - Average Annual Total Returns {Transposed}
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01008 - Schedule - Shareholder Fees
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01009 - Schedule - Annual Fund Operating Expenses
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01010 - Schedule - Expense Example {Transposed}
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01011 - Schedule - Bar Chart [Table]
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01012 - Schedule - Average Annual Total Returns {Transposed}
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01013 - Schedule - Shareholder Fees
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01014 - Schedule - Annual Fund Operating Expenses
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01015 - Schedule - Expense Example {Transposed}
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01016 - Schedule - Bar Chart [Table]
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01017 - Schedule - Average Annual Total Returns {Transposed}
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01018 - Schedule - Shareholder Fees
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01019 - Schedule - Annual Fund Operating Expenses
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01020 - Schedule - Expense Example {Transposed}
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01021 - Schedule - Bar Chart [Table]
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01022 - Schedule - Average Annual Total Returns {Transposed}
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01023 - Schedule - Shareholder Fees
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01024 - Schedule - Annual Fund Operating Expenses
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01025 - Schedule - Expense Example {Transposed}
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01026 - Schedule - Bar Chart [Table]
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01027 - Schedule - Average Annual Total Returns {Transposed}
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01028 - Schedule - Shareholder Fees
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01029 - Schedule - Annual Fund Operating Expenses
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01030 - Schedule - Expense Example {Transposed}
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01031 - Schedule - Bar Chart [Table]
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01032 - Schedule - Average Annual Total Returns {Transposed}
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01033 - Disclosure - Risk/Return Detail Data (Kansas Municipal Fund) {Elements}
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01034 - Document - Risk/Return Summary (Maine Municipal Fund) {Unlabeled}
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01035 - Disclosure - Risk/Return Detail Data (Maine Municipal Fund) {Elements}
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01036 - Document - Risk/Return Summary (Nebraska Municipal Fund) {Unlabeled}
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01037 - Disclosure - Risk/Return Detail Data (Nebraska Municipal Fund) {Elements}
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01038 - Document - Risk/Return Summary (Oklahoma Municipal Fund) {Unlabeled}
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01039 - Disclosure - Risk/Return Detail Data (Oklahoma Municipal Fund) {Elements}
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01040 - Document - Risk/Return Summary (Viking Tax-Free Fund for Montana) {Unlabeled}
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link:definitionLink
01041 - Disclosure - Risk/Return Detail Data (Viking Tax-Free Fund for Montana) {Elements}
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01042 - Document - Risk/Return Summary (Viking Tax-Free Fund for North Dakota) {Unlabeled}
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link:definitionLink
01043 - Disclosure - Risk/Return Detail Data (Viking Tax-Free Fund for North Dakota) {Elements}
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