Shareholder Report, Holdings (Details)	May 31, 2026
C000015135 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[1]
C000015135 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%	[1]
C000015135 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	23.90%	[1]
C000015135 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	35.90%	[1]
C000015135 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%	[1]
C000015135 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.20%	[1]
C000015135 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137678 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[2]
C000137678 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%	[2]
C000137678 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	23.90%	[2]
C000137678 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	35.90%	[2]
C000137678 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%	[2]
C000137678 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.20%	[2]
C000137678 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000015134 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[3]
C000015134 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	13.50%	[3]
C000015134 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	23.90%	[3]
C000015134 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	35.90%	[3]
C000015134 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.30%	[3]
C000015134 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.20%	[3]
C000015134 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000015136 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	5.40%	[4]
C000015136 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[4]
C000015136 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	19.90%	[4]
C000015136 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	34.40%	[4]
C000015136 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	21.40%	[4]
C000015136 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[4]
C000015136 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137679 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	5.40%	[5]
C000137679 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[5]
C000137679 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	19.90%	[5]
C000137679 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	34.40%	[5]
C000137679 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	21.40%	[5]
C000137679 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[5]
C000137679 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000015138 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	5.40%	[6]
C000015138 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	13.80%	[6]
C000015138 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	19.90%	[6]
C000015138 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	34.40%	[6]
C000015138 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	21.40%	[6]
C000015138 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	5.10%	[6]
C000015138 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000015141 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.20%	[7]
C000015141 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[7]
C000015141 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%	[7]
C000015141 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	70.90%	[7]
C000015141 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.60%	[7]
C000015141 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[7]
C000015141 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137680 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.20%	[8]
C000137680 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[8]
C000137680 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%	[8]
C000137680 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	70.90%	[8]
C000137680 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.60%	[8]
C000137680 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[8]
C000137680 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000015139 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.20%	[9]
C000015139 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	7.80%	[9]
C000015139 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	1.30%	[9]
C000015139 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	70.90%	[9]
C000015139 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.60%	[9]
C000015139 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[9]
C000015139 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000015145 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%	[10]
C000015145 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[10]
C000015145 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%	[10]
C000015145 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	63.60%	[10]
C000015145 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.40%	[10]
C000015145 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[10]
C000015145 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137681 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%	[11]
C000137681 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[11]
C000137681 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%	[11]
C000137681 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	63.60%	[11]
C000137681 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.40%	[11]
C000137681 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[11]
C000137681 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000015146 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.10%	[12]
C000015146 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	5.80%	[12]
C000015146 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	10.50%	[12]
C000015146 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	63.60%	[12]
C000015146 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.40%	[12]
C000015146 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	7.60%	[12]
C000015146 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%

[1] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[2] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[3] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below- investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[4] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[5] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[6] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[7] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[8] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[9] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[10] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[11] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.

[12] The ratings disclosed are the highest rating given by one of the following national rating agencies: Standard & Poor’s (S&P), Moody’s Investors Service, Inc. (Moody’s) or Fitch, Inc (Fitch). This treatment of split-rated securities may differ from that used for other purposes, such as for Fund investment policies. Credit ratings are subject to change. AAA, AA, A, and BBB are investment grade ratings; BB, B, CCC, CC, C and D are below-investment grade ratings. Holdings designated N/R are not rated by these national ratings agencies.