Shareholder Report, Average Annual Return (Details)
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12 Months Ended |
60 Months Ended |
117 Months Ended |
120 Months Ended |
Mar. 31, 2026 |
Mar. 31, 2026 |
Mar. 31, 2026 |
Mar. 31, 2026 |
| C000001504 [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 |
4.16%
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1.11%
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2.23%
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| C000000699 [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 |
0.84%
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0.29%
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1.72%
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| C000000700 [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 |
(1.46%)
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(1.41%)
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1.34%
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| C000171394 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class R6 Shares at NAV
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| Average Annual Return, Percent |
3.14%
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(0.34%)
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1.68%
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| C000001507 [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 |
3.02%
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(0.35%)
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1.98%
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| C000001512 [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 |
3.62%
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1.44%
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1.91%
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| C000000702 [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 |
0.93%
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0.74%
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1.45%
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| C000000703 [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 |
(1.62%)
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(0.46%)
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2.62%
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| C000171395 [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
Class R6 Shares at NAV
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| Average Annual Return, Percent |
2.98%
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0.63%
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2.91%
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| C000001515 [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 |
2.87%
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0.60%
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3.26%
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| C000122986 [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 |
2.55%
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2.27%
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3.17%
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| C000122984 [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 |
(0.31%)
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1.55%
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2.71%
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| C000149455 [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 |
(0.23%)
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0.00%
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2.63%
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| C000149457 [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 |
3.00%
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0.81%
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3.14%
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| Without Sales Load [Member] | C000137699 [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 |
3.11%
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0.11%
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1.37%
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| Without Sales Load [Member] | C000000699 [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 |
3.96%
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0.91%
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2.03%
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| Without Sales Load [Member] | C000000700 [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 |
2.89%
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(0.56%)
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1.78%
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| Without Sales Load [Member] | C000137700 [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 |
2.08%
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(1.35%)
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1.12%
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| Without Sales Load [Member] | C000137701 [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 |
2.69%
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0.45%
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1.07%
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| Without Sales Load [Member] | C000000702 [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 |
3.53%
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1.25%
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1.71%
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| Without Sales Load [Member] | C000000703 [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 |
2.72%
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0.40%
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3.06%
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| Without Sales Load [Member] | C000137702 [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 |
1.96%
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(0.40%)
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2.40%
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| Without Sales Load [Member] | C000137704 [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 |
1.51%
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1.26%
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2.32%
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| Without Sales Load [Member] | C000122984 [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 |
2.25%
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2.07%
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2.97%
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| Without Sales Load [Member] | C000149455 [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 |
2.86%
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0.61%
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2.94%
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| Without Sales Load [Member] | C000149456 [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 |
1.94%
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(0.20%)
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2.27%
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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 |
4.32%
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1.08%
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2.03%
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2.25%
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| Lipper 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 Intermediate Municipal Debt Funds Classification Average
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| Average Annual Return, Percent |
4.24%
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1.05%
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1.87%
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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 |
4.71%
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1.18%
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2.19%
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| Lipper General And Insured 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 General & Insured Municipal Debt Funds Classification Average
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| Average Annual Return, Percent |
3.75%
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0.54%
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1.68%
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1.94%
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| S And P Municipal Bond Short 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 Short-Intermediate Index
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| Average Annual Return, Percent |
3.86%
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1.38%
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1.82%
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| Lipper Short 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 Short-Intermediate Municipal Debt Funds Classification Average
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| Average Annual Return, Percent |
3.77%
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1.23%
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1.50%
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| S And P Municipal Yield Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
S&P Municipal Yield Index
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| Average Annual Return, Percent |
3.63%
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1.69%
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3.46%
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3.83%
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| Lipper High Yield 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 High Yield Municipal Debt Funds Classification Average
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| Average Annual Return, Percent |
2.85%
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0.83%
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2.30%
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2.64%
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| S And P Short Duration Municipal Yield Index [Member] |
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| Average Annual Return [Line Items] |
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| Line Graph and Table Measure Name |
S&P Short Duration Municipal Yield Index
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| Average Annual Return, Percent |
3.25%
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2.24%
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3.38%
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