| Form N-CSR Cover | 12 Months Ended |
| Jul. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR/A |
| Amendment Flag | true |
| Amendment Description | This N-CSR filing is amended to include the Report of Independent Registered Public Accountants. |
| Registrant Name | Viking Mutual Funds |
| Entity Central Index Key | 0001082744 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jul. 31, 2024 |
| Shareholder Report | 12 Months Ended | |
| Jul. 31, 2024 USD ($) | ||
| Shareholder Report [Line Items] | ||
| Document Type | N-CSR/A | |
| Amendment Flag | true | |
| Amendment Description | This N-CSR filing is amended to include the Report of Independent Registered Public Accountants. | |
| Registrant Name | Viking Mutual Funds | |
| Entity Central Index Key | 0001082744 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Jul. 31, 2024 | |
| Kansas Municipal Fund | Class A [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Kansas Municipal Fund | |
| Class Name | Class A | |
| Trading Symbol | KSMUX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Kansas Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class A $98 0.98% | |
| Expenses Paid, Amount | $ 98 | |
| Expense Ratio, Percent | 0.98% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class A shares returned 2.09%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted with and without sales charge. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2014 through July 31, 2024 | [1] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class A without sales charge 2.09 -0.15 1.29 Class A with sales charge -0.46 -0.66 1.03 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.47 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 59,000,000 | |
| Holdings Count | 88 | |
| Advisory Fees Paid, Amount | $ 182,000 | |
| Investment Company, Portfolio Turnover | 29% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $59 Number of Holdings 88 Total Advisory Fee $182K Annual Portfolio Turnover 29% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 51.7 A 15.56 Health Care 11.4 AA 59.09 Utilities 9.1 AAA 14.57 Pre-Refunded 8.9 BBB 6.24 Other Revenue 7.3 NR 4.54 Education 6.6 Housing 2.1 Cash Equivalents and Other 1.6 Transportation 1.3 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Kansas Municipal Fund | Class I [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Kansas Municipal Fund | |
| Class Name | Class I | |
| Trading Symbol | KSITX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Kansas Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class I $73 0.73% | |
| Expenses Paid, Amount | $ 73 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class I shares returned 2.45%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE November 1, 2017 through July 31, 2024 | [2] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Inception^ Class I 2.45 0.12 0.98 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.01 ^Inception Date of 11/1/2017 | |
| Performance Inception Date | Nov. 01, 2017 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 59,000,000 | |
| Holdings Count | 88 | |
| Advisory Fees Paid, Amount | $ 182,000 | |
| Investment Company, Portfolio Turnover | 29% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $59 Number of Holdings 88 Total Advisory Fee Paid $182K Annual Portfolio Turnover 29% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 51.7 A 15.56 Health Care 11.4 AA 59.09 Utilities 9.1 AAA 14.57 Pre-Refunded 8.9 BBB 6.24 Other Revenue 7.3 NR 4.54 Education 6.6 Housing 2.1 Cash Equivalents and Other 1.6 Transportation 1.3 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Maine Municipal Fund | Class A [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Maine Municipal Fund | |
| Class Name | Class A | |
| Trading Symbol | MEMUX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Maine Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class A $98 0.98% | |
| Expenses Paid, Amount | $ 98 | |
| Expense Ratio, Percent | 0.98% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class A shares returned 3.05%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted with and without sales charge. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2014 through July 31, 2024 | [3] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class A without sales charge 3.05 -0.55 0.77 Class A with sales charge 0.51 -1.06 0.52 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.47 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 9,000,000 | |
| Holdings Count | 24 | |
| Advisory Fees Paid, Amount | $ 0 | |
| Investment Company, Portfolio Turnover | 69% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $9 Number of Holdings 24 Total Advisory Fee $0 Annual Portfolio Turnover 69% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 27.7 A 9.09 Housing 23.7 AA 90.91 Other Revenue 21.5 Health Care 15.6 Transportation 7.1 Cash Equivalents and Other 4.4 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Maine Municipal Fund | Class I [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Maine Municipal Fund | |
| Class Name | Class I | |
| Trading Symbol | MEIMX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Maine Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class I $73 0.73% | |
| Expenses Paid, Amount | $ 73 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class I shares returned 3.30%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE November 1, 2017 through July 31, 2024 | [4] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Inception^ Class I 3.30 -0.31 0.45 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.01 ^Inception Date of 11/1/2017 | |
| Performance Inception Date | Nov. 01, 2017 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 9,000,000 | |
| Holdings Count | 24 | |
| Advisory Fees Paid, Amount | $ 0 | |
| Investment Company, Portfolio Turnover | 69% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $9 Number of Holdings 24 Total Advisory Fee $0 Annual Portfolio Turnover 69% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 27.7 A 9.09 Housing 23.7 AA 90.91 Other Revenue 21.5 Health Care 15.6 Transportation 7.1 Cash Equivalents and Other 4.4 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Nebraska Municipal Fund | Class A [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Nebraska Municipal Fund | |
| Class Name | Class A | |
| Trading Symbol | NEMUX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Nebraska Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class A $98 0.98% | |
| Expenses Paid, Amount | $ 98 | |
| Expense Ratio, Percent | 0.98% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class A shares returned 1.87%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted with and without sales charge. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2014 through July 31, 2024 | [5] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class A without sales charge 1.87 -0.44 1.19 Class A with sales charge -0.64 -0.94 0.93 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.47 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 33,000,000 | |
| Holdings Count | 51 | |
| Advisory Fees Paid, Amount | $ 83,000 | |
| Investment Company, Portfolio Turnover | 79% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $33 Number of Holdings 51 Total Advisory Fee $83K Annual Portfolio Turnover 79% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 58.0 A 11.49 Education 15.7 AA 58.06 Utilities 11.3 AAA 8.25 Pre-Refunded 7.0 BBB 3.13 Health Care 3.1 NR 19.07 Other Revenue 3.0 Housing 1.2 Cash Equivalents and Other 0.7 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Nebraska Municipal Fund | Class I [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Nebraska Municipal Fund | |
| Class Name | Class I | |
| Trading Symbol | NEITX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Nebraska Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class I $73 0.73% | |
| Expenses Paid, Amount | $ 73 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class I shares returned 2.02%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE November 1, 2017 | [6] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Inception^ Class I 2.02 -0.19 0.74 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.01 ^Inception Date of 11/1/2017 | |
| Performance Inception Date | Nov. 01, 2017 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 33,000,000 | |
| Holdings Count | 51 | |
| Advisory Fees Paid, Amount | $ 83,000 | |
| Investment Company, Portfolio Turnover | 79% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $33 Number of Holdings 51 Total Advisory Fee $83K Annual Portfolio Turnover 79% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 58.0 A 11.49 Education 15.7 AA 58.06 Utilities 11.3 AAA 8.25 Pre-Refunded 7.0 BBB 3.13 Health Care 3.1 NR 19.07 Other Revenue 3.0 Housing 1.2 Cash Equivalents and Other 0.7 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Oklahoma Municipal Fund | Class A [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Oklahoma Municipal Fund | |
| Class Name | Class A | |
| Trading Symbol | OKMUX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Oklahoma Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class A $98 0.98% | |
| Expenses Paid, Amount | $ 98 | |
| Expense Ratio, Percent | 0.98% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class A shares returned 2.33%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted with and without sales charge. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2014 through July 31, 2024 | [7] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class A without sales charge 2.33 -0.28 1.28 Class A with sales charge -0.20 -0.77 1.02 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.47 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 45,000,000 | |
| Holdings Count | 66 | |
| Advisory Fees Paid, Amount | $ 146,000 | |
| Investment Company, Portfolio Turnover | 69% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $45 Number of Holdings 66 Total Advisory Fee $146K Annual Portfolio Turnover 69% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net Other Revenue 69.4 A 32.32 Education 6.4 AA 36.91 Transportation 4.8 AAA 6.67 Cash Equivalents and Other 4.6 BBB 15.85 Housing 4.5 NR 8.25 General Obligation 3.9 Health Care 3.4 Utilities 3.0 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Oklahoma Municipal Fund | Class I [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Oklahoma Municipal Fund | |
| Class Name | Class I | |
| Trading Symbol | OKMIX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Oklahoma Municipal Fund. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class I $73 0.73% | |
| Expenses Paid, Amount | $ 73 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class I shares returned 2.59%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE November 1, 2017 through July 31, 2024 | [8] |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURN (%) 1 Year 5 Years Inception^ Class I 2.59 -0.03 0.90 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.01 ^Inception Date of 11/1/2017 | |
| Performance Inception Date | Nov. 01, 2017 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 45,000,000 | |
| Holdings Count | 66 | |
| Advisory Fees Paid, Amount | $ 146,000 | |
| Investment Company, Portfolio Turnover | 69% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $45 Number of Holdings 66 Total Advisory Fee $146K Annual Portfolio Turnover 69% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net Other Revenue 69.4 A 32.32 Education 6.4 AA 36.91 Transportation 4.8 AAA 6.67 Cash Equivalents and Other 4.6 BBB 15.85 Housing 4.5 NR 8.25 General Obligation 3.9 Health Care 3.4 Utilities 3.0 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Viking Tax-Free Fund for Montana | Class A [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Viking Tax-Free Fund for Montana | |
| Class Name | Class A | |
| Trading Symbol | VMTTX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Viking Tax-Free Fund for Montana. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class A $98 0.98% | |
| Expenses Paid, Amount | $ 98 | |
| Expense Ratio, Percent | 0.98% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class A shares returned 1.98%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted with and without sales charge. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2014 through July 31, 2024 | [9] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class A without sales charge 1.98 -0.02 1.37 Class A with sales charge -0.61 -0.52 1.11 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.47 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 61,000,000 | |
| Holdings Count | 106 | |
| Advisory Fees Paid, Amount | $ 202,000 | |
| Investment Company, Portfolio Turnover | 32% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $61 Number of Holdings 106 Total Advisory Fee $202K Annual Portfolio Turnover 32% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 49.9 A 26.72 Housing 13.7 AA 58.89 Other Revenue 12.6 AAA 1.95 Health Care 12.5 BBB 0.86 Utilities 4.5 NR 11.58 Cash Equivalents and Other 2.3 Pre-Refunded 1.9 Transportation 1.9 Education 0.7 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Viking Tax-Free Fund for Montana | Class I [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Viking Tax-Free Fund for Montana | |
| Class Name | Class I | |
| Trading Symbol | VMTIX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Viking Tax-Free Fund for Montana. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class I $73 0.73% | |
| Expenses Paid, Amount | $ 73 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class I shares returned 2.23%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2016 through July 31, 2024 | [10] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years Inception^ Class I 2.23 0.23 0.89 Bloomberg U.S. Muni Bond Index 3.74 1.19 1.79 ^Inception Date of 8/1/2016 | |
| Performance Inception Date | Aug. 01, 2016 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 61,000,000 | |
| Holdings Count | 106 | |
| Advisory Fees Paid, Amount | $ 202,000 | |
| Investment Company, Portfolio Turnover | 32% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $61 Number of Holdings 106 Total Advisory Fee $202K Annual Portfolio Turnover 32% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 49.9 A 26.72 Housing 13.7 AA 58.89 Other Revenue 12.6 AAA 1.95 Health Care 12.5 BBB 0.86 Utilities 4.5 NR 11.58 Cash Equivalents and Other 2.3 Pre-Refunded 1.9 Transportation 1.9 Education 0.7 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Viking Tax-Free Fund for North Dakota | |
| Class Name | Class A | |
| Trading Symbol | VNDFX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Viking Tax-Free Fund for North Dakota. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class A $98 0.98% | |
| Expenses Paid, Amount | $ 98 | |
| Expense Ratio, Percent | 0.98% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class A shares returned 1.35%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted with and without sales charge. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2014 through July 31, 2024 | [11] |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Class A without sales charge 1.35 -0.64 1.00 Class A with sales charge -1.14 -1.13 0.74 Bloomberg U.S. Muni Bond Index 3.74 1.19 2.47 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 21,000,000 | |
| Holdings Count | 45 | |
| Advisory Fees Paid, Amount | $ 40,000 | |
| Investment Company, Portfolio Turnover | 56% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $21 Number of Holdings 45 Total Advisory Fee $40K Annual Portfolio Turnover 56% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 42.4 A 22.29 Health Care 17.1 AA 51.74 Education 12.9 BBB 7.64 Housing 12.4 NR 18.33 Other Revenue 9.4 Utilities 5.8 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | ||
| Shareholder Report [Line Items] | ||
| Fund Name | Viking Tax-Free Fund for North Dakota | |
| Class Name | Class I | |
| Trading Symbol | VNDIX | |
| Annual or Semi-Annual Statement [Text Block] | This shareholder report contains important information about the Viking Tax-Free Fund for North Dakota. Period covered: August 1, 2023 through July 31, 2024 | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at www.integrityvikingfunds.com/documents or by calling us at (800) 276-1262. | |
| Additional Information Phone Number | (800) 276-1262 | |
| Additional Information Website | www.integrityvikingfunds.com/documents | |
| Expenses [Text Block] | What were the Fund costs for the past year? (Based on a hypothetical $10,000 investment) Class Name Cost of a $10,000 Costs paid as a percentage of a Class I $73 0.73% | |
| Expenses Paid, Amount | $ 73 | |
| Expense Ratio, Percent | 0.73% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform last year? • For the twelve month period ended July 31, 2024, the Fund’s Class I shares returned 1.61%. • In comparison, the Bloomberg U.S. Municipal Bond Index (the Benchmark) returned 3.74% for the same period. What affected the Fund’s performance? • An underweight to lower rated bonds (e.g. BBB) which generally outperformed across most maturities over the period, detracted from relative performance. • An overweight to bonds maturing in roughly 13-20 years, contributed positively to relative performance. • An underweight to higher rated bonds (e.g. AAA) maturing in greater than 25 years, contributed positively to relative performance. | |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years?* The chart below reflects a hypothetical $10,000 investment in the class of shares noted. The chart uses total return NAV performance and assumes reinvestment of dividends and capital gains. Fund expenses, including 12b-1 fees, management fees and other expenses were deducted. CUMULATIVE PERFORMANCE August 1, 2016 through July 31, 2024 | [12] |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURN (%) 1 Year 5 Years Inception^ Class I 1.61 -0.41 0.40 Bloomberg U.S. Muni Bond Index 3.74 1.19 1.79 ^Inception Date of 8/1/2016 | |
| Performance Inception Date | Aug. 01, 2016 | |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | |
| Net Assets | $ 21,000,000 | |
| Holdings Count | 45 | |
| Advisory Fees Paid, Amount | $ 40,000 | |
| Investment Company, Portfolio Turnover | 56% | |
| Additional Fund Statistics [Text Block] | What are some key Fund statistics? (as of July 31, 2024) Total Net Assets (Millions) $21 Number of Holdings 45 Total Advisory Fee $40K Annual Portfolio Turnover 56% | |
| Holdings [Text Block] | What did the Fund invest in? (as of July 31, 2024) Sectors % Net Credit Rating % Net General Obligation 42.4 A 22.29 Health Care 17.1 AA 51.74 Education 12.9 BBB 7.64 Housing 12.4 NR 18.33 Other Revenue 9.4 Utilities 5.8 Additional Fund Statistics Information | |
| Credit Quality Explanation [Text Block] | The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | |
| [1]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[2]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[3]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[4]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[5]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[6]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[7]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[8]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[9]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[10]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[11]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares.[12]The Fund’s past performance is not a good predictor of the Fund’s future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemptions of Fund shares. | ||
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | ||||||||||||
| Jul. 31, 2024 | Jul. 31, 2023 | Jul. 31, 2022 | Jul. 31, 2021 | Jul. 31, 2020 | Jul. 31, 2019 | Jul. 31, 2018 | Nov. 01, 2017 | Jul. 31, 2017 | Aug. 01, 2016 | Jul. 31, 2016 | Jul. 31, 2015 | Jul. 31, 2014 | |
| Kansas Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 12,762 | $ 12,301 | $ 12,188 | $ 13,095 | $ 12,678 | $ 12,031 | $ 11,214 | $ 11,104 | $ 11,075 | $ 10,356 | $ 10,000 | ||
| Kansas Municipal Fund | Class A | KSMUX with maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | KSMUX with maximum sales charge | ||||||||||||
| Account Value | $ 11,084 | 10,856 | 11,076 | 11,861 | 11,737 | 11,167 | 10,566 | 10,532 | 10,576 | 10,044 | 9,748 | ||
| Kansas Municipal Fund | Class A | KSMUX without maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | KSMUX without maximum sales charge | ||||||||||||
| Account Value | $ 11,370 | 11,137 | 11,362 | 12,167 | 12,040 | 11,455 | 10,838 | 10,804 | 10,849 | 10,303 | 10,000 | ||
| Kansas Municipal Fund | Class I | KSITX [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | KSITX | ||||||||||||
| Account Value | $ 10,682 | 10,426 | 10,610 | 11,333 | 11,188 | 10,618 | 10,031 | $ 10,000 | |||||
| Kansas Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 11,440 | 11,027 | 10,926 | 11,739 | 11,365 | 10,785 | 10,053 | 10,000 | |||||
| Maine Municipal Fund | Class A | MEMUX without maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | MEMUX without maximum sales charge | ||||||||||||
| Account Value | $ 10,800 | 10,480 | 10,666 | 11,561 | 11,446 | 11,105 | 10,632 | 10,628 | 10,794 | 10,237 | 10,000 | ||
| Maine Municipal Fund | Class A | MEMUX with maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | MEMUX with maximum sales charge | ||||||||||||
| Account Value | $ 10,532 | 10,220 | 10,401 | 11,274 | 11,162 | 10,829 | 10,368 | 10,364 | 10,526 | 9,983 | 9,752 | ||
| Maine Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 12,762 | 12,301 | 12,188 | 13,095 | 12,678 | 12,031 | 11,214 | 11,104 | 11,075 | 10,356 | 10,000 | ||
| Maine Municipal Fund | Class I | MEIMX [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | MEIMX | ||||||||||||
| Account Value | $ 10,310 | 9,981 | 10,134 | 10,958 | 10,832 | 10,473 | 10,012 | 10,000 | |||||
| Maine Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 11,440 | 11,027 | 10,926 | 11,739 | 11,365 | 10,785 | 10,053 | 10,000 | |||||
| Nebraska Municipal Fund | Class A | NEMUX without maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | NEMUX without maximum sales charge | ||||||||||||
| Account Value | $ 11,259 | 11,052 | 11,227 | 11,993 | 11,948 | 11,510 | 10,895 | 10,858 | 10,969 | 10,354 | 10,000 | ||
| Nebraska Municipal Fund | Class A | NEMUX with maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | NEMUX with maximum sales charge | ||||||||||||
| Account Value | $ 10,974 | 10,772 | 10,943 | 11,690 | 11,646 | 11,219 | 10,619 | 10,583 | 10,692 | 10,092 | 9,747 | ||
| Nebraska Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 12,762 | 12,301 | 12,188 | 13,095 | 12,678 | 12,031 | 11,214 | 11,104 | 11,075 | 10,356 | 10,000 | ||
| Nebraska Municipal Fund | Class I |NEITX [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | NEITX | ||||||||||||
| Account Value | $ 10,512 | 10,304 | 10,441 | 11,116 | 11,046 | 10,615 | 10,032 | 10,000 | |||||
| Nebraska Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 11,440 | 11,027 | 10,926 | 11,739 | 11,365 | 10,785 | 10,053 | 10,000 | |||||
| Oklahoma Municipal Fund | Class A | OKMUX without maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | OKMUX without maximum sales charge | ||||||||||||
| Account Value | $ 11,356 | 11,098 | 11,248 | 12,210 | 11,967 | 11,515 | 10,866 | 10,870 | 10,948 | 10,282 | 10,000 | ||
| Oklahoma Municipal Fund | Class A | OKMUX with maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | OKMUX with maximum sales charge | ||||||||||||
| Account Value | $ 11,070 | 10,818 | 10,965 | 11,902 | 11,665 | 11,225 | 10,592 | 10,596 | 10,672 | 10,023 | 9,748 | ||
| Oklahoma Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 12,762 | 12,301 | 12,188 | 13,095 | 12,678 | 12,031 | 11,214 | 11,104 | 11,075 | 10,356 | 10,000 | ||
| Oklahoma Municipal Fund | Class I | OKMIX [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | OKMIX | ||||||||||||
| Account Value | $ 10,620 | 10,353 | 10,467 | 11,332 | 11,079 | 10,635 | 10,010 | 10,000 | |||||
| Oklahoma Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 11,440 | 11,027 | 10,926 | 11,739 | 11,365 | 10,785 | 10,053 | $ 10,000 | |||||
| Viking Tax-Free Fund for Montana | Class A | VMTTX without maximum sales Charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | VMTTX without maximum sales Charge | ||||||||||||
| Account Value | $ 11,454 | 11,232 | 11,318 | 12,099 | 11,912 | 11,466 | 10,828 | 10,845 | 10,883 | 10,332 | 10,000 | ||
| Viking Tax-Free Fund for Montana | Class A | VMTTX with maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | VMTTX with maximum sales charge | ||||||||||||
| Account Value | $ 11,167 | 10,950 | 11,034 | 11,796 | 11,614 | 11,179 | 10,557 | 10,573 | 10,610 | 10,074 | 9,750 | ||
| Viking Tax-Free Fund for Montana | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 12,762 | 12,301 | 12,188 | 13,095 | 12,678 | 12,031 | 11,214 | 11,104 | 11,075 | 10,356 | 10,000 | ||
| Viking Tax-Free Fund for Montana | Class I | VMTIX [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | VMTIX | ||||||||||||
| Account Value | $ 10,737 | 10,503 | 10,557 | 11,256 | 11,054 | 10,614 | 9,998 | 9,989 | $ 10,000 | ||||
| Viking Tax-Free Fund for Montana | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 11,526 | 11,110 | 11,008 | 11,827 | 11,450 | 10,866 | 10,128 | 10,028 | 10,000 | ||||
| Viking Tax-Free Fund for North Dakota | Class A | VNDFX without maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | VNDFX without maximum sales charge | ||||||||||||
| Account Value | $ 11,043 | 10,895 | 11,138 | 11,937 | 11,752 | 11,402 | 10,849 | 10,855 | 10,921 | 10,349 | 10,000 | ||
| Viking Tax-Free Fund for North Dakota | Class A | VNDFX with maximum sales charge [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | VNDFX with maximum sales charge | ||||||||||||
| Account Value | $ 10,770 | 10,626 | 10,863 | 11,642 | 11,462 | 11,121 | 10,581 | 10,587 | 10,651 | 10,093 | 9,753 | ||
| Viking Tax-Free Fund for North Dakota | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 12,762 | 12,301 | 12,188 | 13,095 | 12,678 | 12,031 | 11,214 | 11,104 | $ 11,075 | $ 10,356 | $ 10,000 | ||
| Viking Tax-Free Fund for North Dakota | Class I | VNDIX [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | VNDIX | ||||||||||||
| Account Value | $ 10,323 | 10,160 | 10,360 | 11,076 | 10,877 | 10,538 | 9,992 | 9,982 | 10,000 | ||||
| Viking Tax-Free Fund for North Dakota | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||||||||
| Account Value | $ 11,526 | $ 11,110 | $ 11,008 | $ 11,827 | $ 11,450 | $ 10,866 | $ 10,128 | $ 10,028 | $ 10,000 |
| Shareholder Report, Average Annual Return (Details) | 12 Months Ended | 60 Months Ended | 81 Months Ended | 96 Months Ended | 120 Months Ended | ||
| Jul. 31, 2024 | Jul. 31, 2024 | Jul. 31, 2024 | Jul. 31, 2024 | Jul. 31, 2024 | |||
| Kansas Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Kansas Municipal Fund | Class A | KSMUX with maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | KSMUX with maximum sales charge | ||||||
| Kansas Municipal Fund | Class A | KSMUX without maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | KSMUX without maximum sales charge | ||||||
| Kansas Municipal Fund | Class A | Class A without sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 2.09% | (0.15%) | 1.29% | ||||
| Kansas Municipal Fund | Class A | Class A with sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | (0.46%) | (0.66%) | 1.03% | ||||
| Kansas Municipal Fund | Class A | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.47% | ||||
| Kansas Municipal Fund | Class I | KSITX [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | KSITX | ||||||
| Kansas Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Kansas Municipal Fund | Class I | Class I [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 2.45% | 0.12% | 0.98% | [1] | |||
| Kansas Municipal Fund | Class I | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.01% | [1] | |||
| Maine Municipal Fund | Class A | MEMUX without maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | MEMUX without maximum sales charge | ||||||
| Maine Municipal Fund | Class A | MEMUX with maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | MEMUX with maximum sales charge | ||||||
| Maine Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Maine Municipal Fund | Class A | Class A without sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.05% | (0.55%) | 0.77% | ||||
| Maine Municipal Fund | Class A | Class A with sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 0.51% | (1.06%) | 0.52% | ||||
| Maine Municipal Fund | Class A | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.47% | ||||
| Maine Municipal Fund | Class I | MEIMX [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | MEIMX | ||||||
| Maine Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Maine Municipal Fund | Class I | Class I [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.30% | (0.31%) | 0.45% | ||||
| Maine Municipal Fund | Class I | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.01% | ||||
| Nebraska Municipal Fund | Class A | NEMUX without maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | NEMUX without maximum sales charge | ||||||
| Nebraska Municipal Fund | Class A | NEMUX with maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | NEMUX with maximum sales charge | ||||||
| Nebraska Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Nebraska Municipal Fund | Class A | Class A without sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 1.87% | (0.44%) | 1.19% | ||||
| Nebraska Municipal Fund | Class A | Class A with sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | (0.64%) | (0.94%) | 0.93% | ||||
| Nebraska Municipal Fund | Class A | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.47% | ||||
| Nebraska Municipal Fund | Class I |NEITX [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | NEITX | ||||||
| Nebraska Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Nebraska Municipal Fund | Class I | Class I [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 2.02% | (0.19%) | 0.74% | [2] | |||
| Nebraska Municipal Fund | Class I | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.01% | [2] | |||
| Oklahoma Municipal Fund | Class A | OKMUX without maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | OKMUX without maximum sales charge | ||||||
| Oklahoma Municipal Fund | Class A | OKMUX with maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | OKMUX with maximum sales charge | ||||||
| Oklahoma Municipal Fund | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Oklahoma Municipal Fund | Class A | Class A without sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 2.33% | (0.28%) | 1.28% | ||||
| Oklahoma Municipal Fund | Class A | Class A with sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | (0.20%) | (0.77%) | 1.02% | ||||
| Oklahoma Municipal Fund | Class A | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.47% | ||||
| Oklahoma Municipal Fund | Class I | OKMIX [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | OKMIX | ||||||
| Oklahoma Municipal Fund | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Oklahoma Municipal Fund | Class I | Class I [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 2.59% | (0.03%) | 0.90% | ||||
| Oklahoma Municipal Fund | Class I | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.01% | ||||
| Viking Tax-Free Fund for Montana | Class A | VMTTX without maximum sales Charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | VMTTX without maximum sales Charge | ||||||
| Viking Tax-Free Fund for Montana | Class A | VMTTX with maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | VMTTX with maximum sales charge | ||||||
| Viking Tax-Free Fund for Montana | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Viking Tax-Free Fund for Montana | Class A | Class A without sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 1.98% | (0.02%) | 1.37% | ||||
| Viking Tax-Free Fund for Montana | Class A | Class A with sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | (0.61%) | (0.52%) | 1.11% | ||||
| Viking Tax-Free Fund for Montana | Class A | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.47% | ||||
| Viking Tax-Free Fund for Montana | Class I | VMTIX [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | VMTIX | ||||||
| Viking Tax-Free Fund for Montana | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Viking Tax-Free Fund for Montana | Class I | Class I [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 2.23% | 0.23% | 0.89% | [3] | |||
| Viking Tax-Free Fund for Montana | Class I | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 1.79% | [3] | |||
| Viking Tax-Free Fund for North Dakota | Class A | VNDFX without maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | VNDFX without maximum sales charge | ||||||
| Viking Tax-Free Fund for North Dakota | Class A | VNDFX with maximum sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | VNDFX with maximum sales charge | ||||||
| Viking Tax-Free Fund for North Dakota | Class A | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Viking Tax-Free Fund for North Dakota | Class A | Class A without sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 1.35% | (0.64%) | 1% | ||||
| Viking Tax-Free Fund for North Dakota | Class A | Class A with sales charge [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | (1.14%) | (1.13%) | 0.74% | ||||
| Viking Tax-Free Fund for North Dakota | Class A | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 2.47% | ||||
| Viking Tax-Free Fund for North Dakota | Class I | VNDIX [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | VNDIX | ||||||
| Viking Tax-Free Fund for North Dakota | Class I | Bloomberg U.S. Municipal Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Line Graph and Table Measure Name | Bloomberg U.S. Municipal Bond Index | ||||||
| Viking Tax-Free Fund for North Dakota | Class I |Class I [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 1.61% | (0.41%) | 0.40% | [4] | |||
| Viking Tax-Free Fund for North Dakota | Class I | Bloomberg U.S. Muni Bond Index [Member] | |||||||
| Average Annual Return [Line Items] | |||||||
| Average Annual Return, Percent | 3.74% | 1.19% | 1.79% | [4] | |||
| [1]Inception Date of 11/1/2017[2]Inception Date of 11/1/2017[3]Inception Date of 8/1/2016[4]Inception Date of 8/1/2016 | |||||||
| Shareholder Report, Holdings (Details) | Jul. 31, 2024 | |
| Kansas Municipal Fund | Class A [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.56% | [1] |
| Kansas Municipal Fund | Class A [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 59.09% | [1] |
| Kansas Municipal Fund | Class A [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 14.57% | [1] |
| Kansas Municipal Fund | Class A [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.24% | [1] |
| Kansas Municipal Fund | Class A [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.54% | [1] |
| Kansas Municipal Fund | Class A [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 51.70% | |
| Kansas Municipal Fund | Class A [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.40% | |
| Kansas Municipal Fund | Class A [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 9.10% | |
| Kansas Municipal Fund | Class A [Member] | Pre-Refunded [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 8.90% | |
| Kansas Municipal Fund | Class A [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.30% | |
| Kansas Municipal Fund | Class A [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.60% | |
| Kansas Municipal Fund | Class A [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.10% | |
| Kansas Municipal Fund | Class A [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.60% | |
| Kansas Municipal Fund | Class A [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.30% | |
| Kansas Municipal Fund | Class I [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.56% | [2] |
| Kansas Municipal Fund | Class I [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 59.09% | [2] |
| Kansas Municipal Fund | Class I [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 14.57% | [2] |
| Kansas Municipal Fund | Class I [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.24% | [2] |
| Kansas Municipal Fund | Class I [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.54% | [2] |
| Kansas Municipal Fund | Class I [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 51.70% | |
| Kansas Municipal Fund | Class I [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.40% | |
| Kansas Municipal Fund | Class I [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 9.10% | |
| Kansas Municipal Fund | Class I [Member] | Pre-Refunded [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 8.90% | |
| Kansas Municipal Fund | Class I [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.30% | |
| Kansas Municipal Fund | Class I [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.60% | |
| Kansas Municipal Fund | Class I [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.10% | |
| Kansas Municipal Fund | Class I [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.60% | |
| Kansas Municipal Fund | Class I [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.30% | |
| Maine Municipal Fund | Class A [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 9.09% | [3] |
| Maine Municipal Fund | Class A [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 90.91% | [3] |
| Maine Municipal Fund | Class A [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 27.70% | |
| Maine Municipal Fund | Class A [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.60% | |
| Maine Municipal Fund | Class A [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 21.50% | |
| Maine Municipal Fund | Class A [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 23.70% | |
| Maine Municipal Fund | Class A [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.40% | |
| Maine Municipal Fund | Class A [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.10% | |
| Maine Municipal Fund | Class I [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 9.09% | [4] |
| Maine Municipal Fund | Class I [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 90.91% | [4] |
| Maine Municipal Fund | Class I [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 27.70% | |
| Maine Municipal Fund | Class I [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.60% | |
| Maine Municipal Fund | Class I [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 21.50% | |
| Maine Municipal Fund | Class I [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 23.70% | |
| Maine Municipal Fund | Class I [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.40% | |
| Maine Municipal Fund | Class I [Member] | Transportation Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.10% | |
| Nebraska Municipal Fund | Class A [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.49% | [5] |
| Nebraska Municipal Fund | Class A [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 58.06% | [5] |
| Nebraska Municipal Fund | Class A [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 8.25% | [5] |
| Nebraska Municipal Fund | Class A [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.13% | [5] |
| Nebraska Municipal Fund | Class A [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 19.07% | [5] |
| Nebraska Municipal Fund | Class A [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 58% | |
| Nebraska Municipal Fund | Class A [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.10% | |
| Nebraska Municipal Fund | Class A [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.30% | |
| Nebraska Municipal Fund | Class A [Member] | Pre-Refunded [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7% | |
| Nebraska Municipal Fund | Class A [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3% | |
| Nebraska Municipal Fund | Class A [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.70% | |
| Nebraska Municipal Fund | Class A [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.20% | |
| Nebraska Municipal Fund | Class A [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | |
| Nebraska Municipal Fund | Class I [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.49% | [6] |
| Nebraska Municipal Fund | Class I [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 58.06% | [6] |
| Nebraska Municipal Fund | Class I [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 8.25% | [6] |
| Nebraska Municipal Fund | Class I [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.13% | [6] |
| Nebraska Municipal Fund | Class I [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 19.07% | [6] |
| Nebraska Municipal Fund | Class I [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 58% | |
| Nebraska Municipal Fund | Class I [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.10% | |
| Nebraska Municipal Fund | Class I [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.30% | |
| Nebraska Municipal Fund | Class I [Member] | Pre-Refunded [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7% | |
| Nebraska Municipal Fund | Class I [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3% | |
| Nebraska Municipal Fund | Class I [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.70% | |
| Nebraska Municipal Fund | Class I [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.20% | |
| Nebraska Municipal Fund | Class I [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | |
| Oklahoma Municipal Fund | Class A [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 32.32% | [7] |
| Oklahoma Municipal Fund | Class A [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 36.91% | [7] |
| Oklahoma Municipal Fund | Class A [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.67% | [7] |
| Oklahoma Municipal Fund | Class A [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.85% | [7] |
| Oklahoma Municipal Fund | Class A [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 8.25% | [7] |
| Oklahoma Municipal Fund | Class A [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.90% | |
| Oklahoma Municipal Fund | Class A [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.40% | |
| Oklahoma Municipal Fund | Class A [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 69.40% | |
| Oklahoma Municipal Fund | Class A [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.40% | |
| Oklahoma Municipal Fund | Class A [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.50% | |
| Oklahoma Municipal Fund | Class A [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.60% | |
| Oklahoma Municipal Fund | Class A [Member] | Transportation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.80% | |
| Oklahoma Municipal Fund | Class A [Member] | Utilities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3% | |
| Oklahoma Municipal Fund | Class I [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 32.32% | [8] |
| Oklahoma Municipal Fund | Class I [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 36.91% | [8] |
| Oklahoma Municipal Fund | Class I [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.67% | [8] |
| Oklahoma Municipal Fund | Class I [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 15.85% | [8] |
| Oklahoma Municipal Fund | Class I [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 8.25% | [8] |
| Oklahoma Municipal Fund | Class I [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.90% | |
| Oklahoma Municipal Fund | Class I [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3.40% | |
| Oklahoma Municipal Fund | Class I [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 69.40% | |
| Oklahoma Municipal Fund | Class I [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 6.40% | |
| Oklahoma Municipal Fund | Class I [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.50% | |
| Oklahoma Municipal Fund | Class I [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.60% | |
| Oklahoma Municipal Fund | Class I [Member] | Transportation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.80% | |
| Oklahoma Municipal Fund | Class I [Member] | Utilities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 3% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 26.72% | [9] |
| Viking Tax-Free Fund for Montana | Class A [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 58.89% | [9] |
| Viking Tax-Free Fund for Montana | Class A [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.95% | [9] |
| Viking Tax-Free Fund for Montana | Class A [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.86% | [9] |
| Viking Tax-Free Fund for Montana | Class A [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.58% | [9] |
| Viking Tax-Free Fund for Montana | Class A [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 49.90% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.50% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Pre-Refunded [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.90% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.60% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 13.70% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.30% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Transportation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.90% | |
| Viking Tax-Free Fund for Montana | Class A [Member] | Utilities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.50% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 26.72% | [10] |
| Viking Tax-Free Fund for Montana | Class I [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 58.89% | [10] |
| Viking Tax-Free Fund for Montana | Class I [Member] | AAA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.95% | [10] |
| Viking Tax-Free Fund for Montana | Class I [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.86% | [10] |
| Viking Tax-Free Fund for Montana | Class I [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 11.58% | [10] |
| Viking Tax-Free Fund for Montana | Class I [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 49.90% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.50% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Utilities Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 4.50% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Pre-Refunded [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.90% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.60% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 0.70% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 13.70% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Cash Equivalents and Other [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 2.30% | |
| Viking Tax-Free Fund for Montana | Class I [Member] | Transportation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 1.90% | |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 22.29% | [11] |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 51.74% | [11] |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.64% | [11] |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 18.33% | [11] |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 42.40% | |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 17.10% | |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 9.40% | |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.90% | |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.40% | |
| Viking Tax-Free Fund for North Dakota | Class A [Member] | Utilities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 5.80% | |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | A [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 22.29% | [12] |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | AA [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 51.74% | [12] |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | BBB [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 7.64% | [12] |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | NR [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 18.33% | [12] |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | General Obligation [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 42.40% | |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | Healthcare Sector [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 17.10% | |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | Other Revenue [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 9.40% | |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | Education [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.90% | |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | Housing [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 12.40% | |
| Viking Tax-Free Fund for North Dakota | Class I [Member] | Utilities [Member] | ||
| Holdings [Line Items] | ||
| Percent of Net Asset Value | 5.80% | |
| [1]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[2]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[3]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[4]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[5]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[6]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[7]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[8]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[9]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[10]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[11]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change.[12]The ratings agencies that provided the ratings are Standard & Poor’s and Moody’s. When ratings vary, the higher rating is used. Credit quality ratings are measured on a scale that generally ranges from AAA (highest) to D (lowest). “NR” is used to classify securities for which a rating is not available. Ratings apply to the holdings in the Fund portfolio and not to the Fund or its shares. Ratings are subject to change. | ||
