v3.25.2
Shareholder Report, Average Annual Return (Details)
 12 Months Ended 60 Months Ended 98 Months Ended 120 Months Ended
May 31, 2025
May 31, 2025
May 31, 2025
May 31, 2025
C000017685 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.05% 2.06%   2.89%
C000088012 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.25% 2.27%   3.10%
C000189766 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.16% 2.28% 2.88%  
C000017686 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent (2.79%) 0.88%   2.16%
C000017688 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 0.92% 1.03%   1.87%
C000017689 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.27% 1.04%   1.92%
C000017691 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.57% 1.24%   2.12%
C000189767 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.60% 1.27% 2.12%  
C000088013 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent (2.49%) (0.12%)   1.20%
C000088014 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 1.35% 0.05%   0.91%
Without Sales Load [Member] | C000017686 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 1.80% 1.81%   2.64%
Without Sales Load [Member] | C000088013 [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.11% 0.81%   1.67%
S&P National AMT-Free Municipal [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 1.64% 0.53% 1.90% 2.08%
S&P National AMT-Free Municipal (Inception Date 4/10/17) [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 1.64% 0.53% 1.90%  
S&P Municipal Bond 50% Investment Grade/50% High Yield [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.98% 2.05% 2.88% 3.18%
S&P Intermediate Term National AMT-Free Municipal [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.63% 0.86%   2.04%
S&P Intermediate Term National AMT-Free Municipal (Inception Date 4/10/17) [Member]        
Average Annual Return [Line Items]        
Average Annual Return, Percent 2.63% 0.86% 1.94%