Shareholder Report, Average Annual Return (Details)
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12 Months Ended |
60 Months Ended |
120 Months Ended |
May 31, 2025 |
May 31, 2025 |
May 31, 2025 |
| C000015145 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at maximum sales charge (Offering Price)
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| Average Annual Return, Percent |
(0.92%)
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(0.50%)
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1.17%
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| C000015146 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class I Shares at NAV
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| Average Annual Return, Percent |
2.38%
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0.32%
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1.69%
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| C000015139 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at maximum sales charge (Offering Price)
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| Average Annual Return, Percent |
(3.66%)
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(1.78%)
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0.75%
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| C000015141 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class I Shares at NAV
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| Average Annual Return, Percent |
0.62%
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(0.74%)
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1.37%
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| C000015138 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class I Shares at NAV
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| Average Annual Return, Percent |
1.61%
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0.49%
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2.03%
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| C000015136 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at maximum sales charge (Offering Price)
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| Average Annual Return, Percent |
(2.88%)
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(0.57%)
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1.39%
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| C000015134 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at maximum sales charge (Offering Price)
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| Average Annual Return, Percent |
(0.57%)
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0.03%
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1.46%
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| C000015135 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class I Shares at NAV
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| Average Annual Return, Percent |
2.74%
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0.84%
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1.98%
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| Without Sales Load [Member] | C000015145 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
2.16%
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0.11%
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1.48%
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| Without Sales Load [Member] | C000137681 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class C Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
1.44%
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(0.68%)
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0.83%
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| Without Sales Load [Member] | C000015139 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
0.53%
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(0.93%)
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1.18%
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| Without Sales Load [Member] | C000137680 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class C Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
(0.31%)
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(1.70%)
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0.54%
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| Without Sales Load [Member] | C000015136 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
1.41%
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0.29%
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1.83%
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| Without Sales Load [Member] | C000137679 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class C Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
0.59%
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(0.52%)
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1.17%
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| Without Sales Load [Member] | C000015134 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class A Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
2.54%
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0.63%
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1.77%
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| Without Sales Load [Member] | C000137678 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class C Shares at NAV (excluding maximum sales charge)
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| Average Annual Return, Percent |
1.73%
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(0.15%)
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1.12%
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| S And P Municipal Bond Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
S&P Municipal Bond Index
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| Average Annual Return, Percent |
2.44%
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0.78%
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2.22%
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| Lipper Other States Intermediate Municipal Debt Funds Classification Average [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Lipper Other States Intermediate Municipal Debt Funds Classification Average
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| Average Annual Return, Percent |
2.36%
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0.02%
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1.31%
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| S And P Municipal Bond Intermediate Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
S&P Municipal Bond Intermediate Index
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| Average Annual Return, Percent |
3.48%
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0.80%
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2.20%
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| Lipper Other States Municipal Debt Funds Classification Average [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Lipper Other States Municipal Debt Funds Classification Average
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| Average Annual Return, Percent |
0.90%
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(0.12%)
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1.32%
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| S And P Municipal Bond Nebraska Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
S&P Municipal Bond Nebraska Index
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| Average Annual Return, Percent |
2.55%
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0.29%
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2.06%
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| S And P Municipal Bond Minnesota Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
S&P Municipal Bond Minnesota Index
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| Average Annual Return, Percent |
3.01%
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0.63%
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1.99%
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| Lipper Minnesota Municipal Debt Funds Classification Average [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Lipper Minnesota Municipal Debt Funds Classification Average
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| Average Annual Return, Percent |
1.25%
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0.01%
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1.38%
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