Shareholder Report, Holdings (Details)	Aug. 31, 2024
C000001516 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[1]
C000001516 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	19.70%	[1]
C000001516 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%	[1]
C000001516 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[1]
C000001516 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%	[1]
C000001516 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	24.00%	[1]
C000001516 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137687 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[2]
C000137687 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	19.70%	[2]
C000137687 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%	[2]
C000137687 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[2]
C000137687 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%	[2]
C000137687 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	24.00%	[2]
C000137687 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001519 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[3]
C000001519 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	19.70%	[3]
C000001519 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	10.10%	[3]
C000001519 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	5.30%	[3]
C000001519 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	37.10%	[3]
C000001519 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	24.00%	[3]
C000001519 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001524 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[4]
C000001524 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	7.20%	[4]
C000001524 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.40%	[4]
C000001524 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[4]
C000001524 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	48.40%	[4]
C000001524 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	26.20%	[4]
C000001524 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137688 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[5]
C000137688 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	7.20%	[5]
C000137688 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.40%	[5]
C000137688 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[5]
C000137688 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	48.40%	[5]
C000137688 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	26.20%	[5]
C000137688 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001527 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	3.70%	[6]
C000001527 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	7.20%	[6]
C000001527 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.40%	[6]
C000001527 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	6.10%	[6]
C000001527 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	48.40%	[6]
C000001527 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	26.20%	[6]
C000001527 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001528 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%	[7]
C000001528 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	6.60%	[7]
C000001528 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%	[7]
C000001528 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	15.00%	[7]
C000001528 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	51.60%	[7]
C000001528 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	13.70%	[7]
C000001528 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137689 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%	[8]
C000137689 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	6.60%	[8]
C000137689 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%	[8]
C000137689 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	15.00%	[8]
C000137689 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	51.60%	[8]
C000137689 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	13.70%	[8]
C000137689 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001531 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	1.80%	[9]
C000001531 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	6.60%	[9]
C000001531 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%	[9]
C000001531 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	15.00%	[9]
C000001531 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	51.60%	[9]
C000001531 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	13.70%	[9]
C000001531 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001536 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%	[10]
C000001536 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	6.60%	[10]
C000001536 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%	[10]
C000001536 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%	[10]
C000001536 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	42.90%	[10]
C000001536 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	23.90%	[10]
C000001536 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137690 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%	[11]
C000137690 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	6.60%	[11]
C000137690 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%	[11]
C000137690 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%	[11]
C000137690 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	42.90%	[11]
C000137690 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	23.90%	[11]
C000137690 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001539 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	2.10%	[12]
C000001539 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	6.60%	[12]
C000001539 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	11.30%	[12]
C000001539 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	13.20%	[12]
C000001539 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	42.90%	[12]
C000001539 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	23.90%	[12]
C000001539 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001540 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[13]
C000001540 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%	[13]
C000001540 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	24.60%	[13]
C000001540 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[13]
C000001540 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	41.10%	[13]
C000001540 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.10%	[13]
C000001540 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000137691 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[14]
C000137691 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%	[14]
C000137691 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	24.60%	[14]
C000137691 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[14]
C000137691 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	41.10%	[14]
C000137691 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.10%	[14]
C000137691 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000001543 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	6.50%	[15]
C000001543 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	9.50%	[15]
C000001543 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	24.60%	[15]
C000001543 [Member] | Standard & Poor's, AAA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	4.20%	[15]
C000001543 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	41.10%	[15]
C000001543 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	14.10%	[15]
C000001543 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	100.00%
C000023361 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[16]
C000023361 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	48.50%	[16]
C000023361 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.00%	[16]
C000023361 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[16]
C000023361 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	22.70%	[16]
C000023361 [Member] | N A not applicable [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[16]
C000023361 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	96.20%	[17]
C000023361 [Member] | Short Term Repurchase Agreements [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[17]
C000137692 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[18]
C000137692 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	48.50%	[18]
C000137692 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.00%	[18]
C000137692 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[18]
C000137692 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	22.70%	[18]
C000137692 [Member] | N A not applicable [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[18]
C000137692 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	96.20%	[19]
C000137692 [Member] | Short Term Repurchase Agreements [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[19]
C000023364 [Member] | BB or Lower [Member]
Holdings [Line Items]
Percent of Total Investments	7.40%	[20]
C000023364 [Member] | N R not rated [Member]
Holdings [Line Items]
Percent of Total Investments	48.50%	[20]
C000023364 [Member] | Standard & Poor's, BBB Rating [Member]
Holdings [Line Items]
Percent of Total Investments	8.00%	[20]
C000023364 [Member] | Standard & Poor's, AA Rating [Member]
Holdings [Line Items]
Percent of Total Investments	9.60%	[20]
C000023364 [Member] | Standard & Poor's, A Rating [Member]
Holdings [Line Items]
Percent of Total Investments	22.70%	[20]
C000023364 [Member] | N A not applicable [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[20]
C000023364 [Member] | Municipal Bonds [Member]
Holdings [Line Items]
Percent of Total Investments	96.20%	[21]
C000023364 [Member] | Short Term Repurchase Agreements [Member]
Holdings [Line Items]
Percent of Total Investments	3.80%	[21]

[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.

[13] 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.

[14] 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.

[15] 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.

[16] The ratings disclosed are the lowest 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.

[17] Total investments include the Fund’s assets attributable to financial leverage. For these purposes, financial leverage includes the Fund’s investments in the residual interest certificates (also called inverse floating rate securities) in tender option bond (TOB) trusts, including the portion of assets held by a TOB trust that has been effectively financed by the trust’s issuance of floating rate securities.

[18] The ratings disclosed are the lowest 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.

[19] Total investments include the Fund’s assets attributable to financial leverage. For these purposes, financial leverage includes the Fund’s investments in the residual interest certificates (also called inverse floating rate securities) in tender option bond (TOB) trusts, including the portion of assets held by a TOB trust that has been effectively financed by the trust’s issuance of floating rate securities.

[20] The ratings disclosed are the lowest 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.

[21] Total investments include the Fund’s assets attributable to financial leverage. For these purposes, financial leverage includes the Fund’s investments in the residual interest certificates (also called inverse floating rate securities) in tender option bond (TOB) trusts, including the portion of assets held by a TOB trust that has been effectively financed by the trust’s issuance of floating rate securities.