| Form N-CSR Cover | 12 Months Ended |
| Aug. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | DELAWARE GROUP TAX FREE FUND |
| Entity Central Index Key | 0000728352 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Aug. 31, 2024 |
| Shareholder Report | 12 Months Ended |
| Aug. 31, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | DELAWARE GROUP TAX FREE FUND |
| Entity Central Index Key | 0000728352 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Aug. 31, 2024 |
| C000006385 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | Delaware Tax-Free USA Fund |
| Class Name | Class A |
| Trading Symbol | DMTFX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Delaware Tax-Free USA Fund (Fund) for the period of September 1, 2023, to August 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at delawarefunds.com/literature. You can also request this information by contacting us at 800 523-1918, weekdays from 8:30am to 6:00pm ET. |
| Additional Information Phone Number | 800 523-1918 |
| Additional Information Website | delawarefunds.com/literature |
| Expenses [Text Block] | What were the Fund's costs for the last 12 months? (Based on a hypothetical $10,000 investment) Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class A $ 0.80 % |
| Expenses Paid, Amount | $ 85 |
| Expense Ratio, Percent | 0.80% |
| Factors Affecting Performance [Text Block] | Management’s discussion of Fund performance Performance highlights Delaware Tax-Free USA Fund (Class A) returned 11.99% (excluding sales charge) for the 12 months ended August 31, 2024. Top contributors to performance: Municipal yields fell over the fiscal year against a backdrop of slowing inflation and anticipation that the US Federal Reserve (Fed) would eventually cut rates. As a result, the longer end of the curve outperformed. Lower-investment-grade and below-investment-grade segments drove performance. The catalyst was a strong technical backdrop of diminutive high yield issuance coupled with inflows to municipal mutual funds, particularly high yield funds. Key contributors to performance included: Overweight to the long bond (22+ years) segment of the curve Overweight to BBB-rated credit Meaningful out-of-benchmark allocation to below-investment-grade securities Top detractors from performance: The front end of the curve – which is, by its nature, shorter in duration – detracted from performance over the fiscal year, as this maturity segment lagged relative to the intermediate and long ends of the curve. Key detractors from performance included: Modest out-of-benchmark allocation to the front end (0-1 year) of the curve Allocation to pre-refunded bonds, predominantly on the front end of the curve |
| Performance Past Does Not Indicate Future [Text] | Keep in mind that the Fund's past performance is not a good predictor of how the Fund will perform in the future. |
| Line Graph [Table Text Block] | Fund performance The following graph compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years of the Class. It also assumes a $10,000 initial investment at the beginning of the first full fiscal year in a broad-based Growth of $10,000 investment For the period August 31, 2014, through August 31, 2024 |
| Average Annual Return [Table Text Block] | Average annual total returns (as of August 31, 2024) 1 year 5 year 10 year Delaware Tax-Free USA Fund (Class A) – including sales charge 6.97 % 0.91 % 2.45 % Delaware Tax-Free USA Fund (Class A) – excluding sales charge 11.99 % 1.84 % 2.92 % Bloomberg Municipal Bond Index 6.09 % 1.02 % 2.43 % |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. |
| Updated Performance Information Location [Text Block] | Visit delawarefunds.com/performance for the most recent performance information. |
| Net Assets | $ 1,220,921,586 |
| Holdings Count | Holding | 288 |
| Advisory Fees Paid, Amount | $ 4,579,455 |
| Investment Company Portfolio Turnover | 28% |
| Additional Fund Statistics [Text Block] | Fund statistics Fund net assets $ Total number of portfolio holdings 288 Total advisory fees paid $ Portfolio turnover rate 28 % |
| Holdings [Text Block] | Fund holdings The tables below show the investment makeup of the Fund, with each category representing a percentage of the total net assets of the Fund. Sector allocation Special Tax Revenue Bonds 16.49 % Industrial Development Revenue/Pollution Control 15.91 % Healthcare Revenue Bonds 13.75 % Education Revenue Bonds 12.24 % Transportation Revenue Bonds 11.70 % Lease Revenue Bonds 7.31 % State General Obligation Bonds 6.39 % Housing Revenue Bonds 5.31 % Local General Obligation Bonds 3.60 % Electric Revenue Bonds 2.19 % State and territory allocation California 13.91 % Puerto Rico 13.87 % New York 9.86 % Illinois 9.21 % Florida 6.84 % Texas 3.98 % Pennsylvania 3.84 % Arizona 3.65 % Colorado 3.49 % Ohio 2.77 % |
| C000006387 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | Delaware Tax-Free USA Fund |
| Class Name | Class C |
| Trading Symbol | DUSCX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Delaware Tax-Free USA Fund (Fund) for the period of September 1, 2023, to August 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at delawarefunds.com/literature. You can also request this information by contacting us at 800 523-1918, weekdays from 8:30am to 6:00pm ET. |
| Additional Information Phone Number | 800 523-1918 |
| Additional Information Website | delawarefunds.com/literature |
| Expenses [Text Block] | What were the Fund's costs for the last 12 months? (Based on a hypothetical $10,000 investment) Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class C $ 1.55 % |
| Expenses Paid, Amount | $ 164 |
| Expense Ratio, Percent | 1.55% |
| Factors Affecting Performance [Text Block] | Management’s discussion of Fund performance Performance highlights Delaware Tax-Free USA Fund (Class C) returned 11.15% (excluding sales charge) for the 12 months ended August 31, 2024. Top contributors to performance: Municipal yields fell over the fiscal year against a backdrop of slowing inflation and anticipation that the US Federal Reserve (Fed) would eventually cut rates. As a result, the longer end of the curve outperformed. Lower-investment-grade and below-investment-grade segments drove performance. The catalyst was a strong technical backdrop of diminutive high yield issuance coupled with inflows to municipal mutual funds, particularly high yield funds. Key contributors to performance included: Overweight to the long bond (22+ years) segment of the curve Overweight to BBB-rated credit Meaningful out-of-benchmark allocation to below-investment-grade securities Top detractors from performance: The front end of the curve – which is, by its nature, shorter in duration – detracted from performance over the fiscal year, as this maturity segment lagged relative to the intermediate and long ends of the curve. Key detractors from performance included: Modest out-of-benchmark allocation to the front end (0-1 year) of the curve Allocation to pre-refunded bonds, predominantly on the front end of the curve |
| Performance Past Does Not Indicate Future [Text] | Keep in mind that the Fund's past performance is not a good predictor of how the Fund will perform in the future. |
| Line Graph [Table Text Block] | Fund performance The following graph compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years of the Class. It also assumes a $10,000 initial investment at the beginning of the first full fiscal year in a broad-based Growth of $10,000 investment For the period August 31, 2014, through August 31, 2024 |
| Average Annual Return [Table Text Block] | Average annual total returns (as of August 31, 2024) 1 year 5 year 10 year Delaware Tax-Free USA Fund (Class C) – including sales charge 10.15 % 1.08 % 2.14 % Delaware Tax-Free USA Fund (Class C) – excluding sales charge 11.15 % 1.08 % 2.14 % Bloomberg Municipal Bond Index 6.09 % 1.02 % 2.43 % |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. |
| Updated Performance Information Location [Text Block] | Visit delawarefunds.com/performance for the most recent performance information. |
| Net Assets | $ 1,220,921,586 |
| Holdings Count | Holding | 288 |
| Advisory Fees Paid, Amount | $ 4,579,455 |
| Investment Company Portfolio Turnover | 28% |
| Additional Fund Statistics [Text Block] | Fund statistics Fund net assets $ Total number of portfolio holdings 288 Total advisory fees paid $ Portfolio turnover rate 28 % |
| Holdings [Text Block] | Fund holdings The tables below show the investment makeup of the Fund, with each category representing a percentage of the total net assets of the Fund. Sector allocation Special Tax Revenue Bonds 16.49 % Industrial Development Revenue/Pollution Control 15.91 % Healthcare Revenue Bonds 13.75 % Education Revenue Bonds 12.24 % Transportation Revenue Bonds 11.70 % Lease Revenue Bonds 7.31 % State General Obligation Bonds 6.39 % Housing Revenue Bonds 5.31 % Local General Obligation Bonds 3.60 % Electric Revenue Bonds 2.19 % State and territory allocation California 13.91 % Puerto Rico 13.87 % New York 9.86 % Illinois 9.21 % Florida 6.84 % Texas 3.98 % Pennsylvania 3.84 % Arizona 3.65 % Colorado 3.49 % Ohio 2.77 % |
| C000074146 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | Delaware Tax-Free USA Fund |
| Class Name | Institutional Class |
| Trading Symbol | DTFIX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Delaware Tax-Free USA Fund (Fund) for the period of September 1, 2023, to August 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at delawarefunds.com/literature. You can also request this information by contacting us at 800 523-1918, weekdays from 8:30am to 6:00pm ET. |
| Additional Information Phone Number | 800 523-1918 |
| Additional Information Website | delawarefunds.com/literature |
| Expenses [Text Block] | What were the Fund's costs for the last 12 months? (Based on a hypothetical $10,000 investment) Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Institutional Class $ 0.55 % |
| Expenses Paid, Amount | $ 58 |
| Expense Ratio, Percent | 0.55% |
| Factors Affecting Performance [Text Block] | Management’s discussion of Fund performance Performance highlights Delaware Tax-Free USA Fund (Institutional Class) returned 12.21% (excluding sales charge) for the 12 months ended August 31, 2024. Top contributors to performance: Municipal yields fell over the fiscal year against a backdrop of slowing inflation and anticipation that the US Federal Reserve (Fed) would eventually cut rates. As a result, the longer end of the curve outperformed. Lower-investment-grade and below-investment-grade segments drove performance. The catalyst was a strong technical backdrop of diminutive high yield issuance coupled with inflows to municipal mutual funds, particularly high yield funds. Key contributors to performance included: Overweight to the long bond (22+ years) segment of the curve Overweight to BBB-rated credit Meaningful out-of-benchmark allocation to below-investment-grade securities Top detractors from performance: The front end of the curve – which is, by its nature, shorter in duration – detracted from performance over the fiscal year, as this maturity segment lagged relative to the intermediate and long ends of the curve. Key detractors from performance included: Modest out-of-benchmark allocation to the front end (0-1 year) of the curve Allocation to pre-refunded bonds, predominantly on the front end of the curve |
| Performance Past Does Not Indicate Future [Text] | Keep in mind that the Fund's past performance is not a good predictor of how the Fund will perform in the future. |
| Line Graph [Table Text Block] | Fund performance The following graph compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years of the Class. It also assumes a $10,000 initial investment at the beginning of the first full fiscal year in a broad-based Growth of $10,000 investment For the period August 31, 2014, through August 31, 2024 |
| Average Annual Return [Table Text Block] | Average annual total returns (as of August 31, 2024) 1 year 5 year 10 year Delaware Tax-Free USA Fund (Institutional Class) – including sales charge 12.21 % 2.09 % 3.17 % Delaware Tax-Free USA Fund (Institutional Class) – excluding sales charge 12.21 % 2.09 % 3.17 % Bloomberg Municipal Bond Index 6.09 % 1.02 % 2.43 % |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. |
| Updated Performance Information Location [Text Block] | Visit delawarefunds.com/performance for the most recent performance information. |
| Net Assets | $ 1,220,921,586 |
| Holdings Count | Holding | 288 |
| Advisory Fees Paid, Amount | $ 4,579,455 |
| Investment Company Portfolio Turnover | 28% |
| Additional Fund Statistics [Text Block] | Fund statistics Fund net assets $ Total number of portfolio holdings 288 Total advisory fees paid $ Portfolio turnover rate 28 % |
| Holdings [Text Block] | Fund holdings The tables below show the investment makeup of the Fund, with each category representing a percentage of the total net assets of the Fund. Sector allocation Special Tax Revenue Bonds 16.49 % Industrial Development Revenue/Pollution Control 15.91 % Healthcare Revenue Bonds 13.75 % Education Revenue Bonds 12.24 % Transportation Revenue Bonds 11.70 % Lease Revenue Bonds 7.31 % State General Obligation Bonds 6.39 % Housing Revenue Bonds 5.31 % Local General Obligation Bonds 3.60 % Electric Revenue Bonds 2.19 % State and territory allocation California 13.91 % Puerto Rico 13.87 % New York 9.86 % Illinois 9.21 % Florida 6.84 % Texas 3.98 % Pennsylvania 3.84 % Arizona 3.65 % Colorado 3.49 % Ohio 2.77 % |
| C000006388 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | Delaware Tax-Free USA Intermediate Fund |
| Class Name | Class A |
| Trading Symbol | DMUSX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Delaware Tax-Free USA Intermediate Fund (Fund) for the period of September 1, 2023, to August 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at delawarefunds.com/literature. You can also request this information by contacting us at 800 523-1918, weekdays from 8:30am to 6:00pm ET. |
| Additional Information Phone Number | 800 523-1918 |
| Additional Information Website | delawarefunds.com/literature |
| Expenses [Text Block] | What were the Fund's costs for the last 12 months? (Based on a hypothetical $10,000 investment) Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class A $ 0.75 % |
| Expenses Paid, Amount | $ 78 |
| Expense Ratio, Percent | 0.75% |
| Factors Affecting Performance [Text Block] | Management’s discussion of Fund performance Performance highlights Delaware Tax-Free USA Intermediate Fund (Class A) returned 9.15% (excluding sales charge) for the 12 months ended August 31, 2024. Top contributors to performance: Municipal yields fell over the fiscal year against a backdrop of slowing inflation and anticipation that the US Federal Reserve (Fed) would eventually cut rates. As a result, the longer end of the curve outperformed. Lower-investment-grade and below-investment-grade segments drove performance. The catalyst was a strong technical backdrop of diminutive high yield issuance coupled with inflows to municipal mutual funds, particularly high yield funds. Key contributors to performance included: Out-of-benchmark allocation to the 17+ years segment of the curve relative to the Fund's secondary benchmark Overweight to BBB-rated credit relative to the Fund's primary benchmark Meaningful out-of-benchmark allocation to below-investment-grade securities relative to the Fund's benchmarks Top detractors from performance: The front end of the curve – which is, by its nature, shorter in duration – detracted from performance over the fiscal year, as this maturity segment lagged relative to the intermediate and long ends of the curve. Key detractors from performance relative to the Fund's secondary benchmark included: Modest out-of-benchmark allocation to the front end (0-1 year) of the curve Allocation to pre-refunded bonds, predominantly on the front end of the curve |
| Performance Past Does Not Indicate Future [Text] | Keep in mind that the Fund's past performance is not a good predictor of how the Fund will perform in the future. |
| Line Graph [Table Text Block] | Fund performance The following graph compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years of the Class. It also assumes a $10,000 initial investment at the beginning of the first full fiscal year in a broad-based Growth of $10,000 investment For the period August 31, 2014, through August 31, 2024 |
| Average Annual Return [Table Text Block] | Average annual total returns (as of August 31, 2024) 1 year 5 year 10 year Delaware Tax-Free USA Intermediate Fund (Class A) – including sales charge 6.17 % 0.72 % 1.92 % Delaware Tax-Free USA Intermediate Fund (Class A) – excluding sales charge 9.15 % 1.28 % 2.20 % Bloomberg Municipal Bond Index 6.09 % 1.02 % 2.43 % Bloomberg 3–15 Year Blend Municipal Bond Index 5.26 % 1.10 % 2.25 % |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. |
| Performance Table Market Index Changed [Text Block] | In connection with new regulatory requirements, effective the date of this report, the Fund changed its broad-based securities market benchmark index to the Bloomberg Municipal Bond Index. Although the Bloomberg Municipal Bond Index can be considered broadly representative of the overall securities market applicable to the Fund, the Fund will continue to show the performance of the Bloomberg 3–15 Year Blend Municipal Bond Index for comparative purposes because the Delaware Management Company, the Fund's manager, believes it is more representative of the Fund’s investment universe. |
| Updated Performance Information Location [Text Block] | Visit delawarefunds.com/performance for the most recent performance information. |
| Net Assets | $ 1,213,278,557 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 4,204,145 |
| Investment Company Portfolio Turnover | 28% |
| Additional Fund Statistics [Text Block] | Fund statistics Fund net assets $ Total number of portfolio holdings 453 Total advisory fees paid $ Portfolio turnover rate 28 % |
| Holdings [Text Block] | Fund holdings The tables below show the investment makeup of the Fund, with each category representing a percentage of the total net assets of the Fund. Sector allocation Industrial Development Revenue/Pollution Control 19.18 % Transportation Revenue Bonds 16.10 % Special Tax Revenue Bonds 13.80 % State General Obligation Bonds 9.90 % Lease Revenue Bonds 8.45 % Healthcare Revenue Bonds 8.15 % Education Revenue Bonds 6.82 % Local General Obligation Bonds 4.86 % Electric Revenue Bonds 4.20 % Housing Revenue Bonds 4.13 % State and territory allocation New York 15.15 % Puerto Rico 10.67 % California 10.24 % Illinois 9.74 % Florida 6.21 % New Jersey 5.31 % Colorado 4.37 % Arizona 4.01 % Pennsylvania 3.49 % Texas 3.12 % |
| C000006390 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | Delaware Tax-Free USA Intermediate Fund |
| Class Name | Class C |
| Trading Symbol | DUICX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Delaware Tax-Free USA Intermediate Fund (Fund) for the period of September 1, 2023, to August 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at delawarefunds.com/literature. You can also request this information by contacting us at 800 523-1918, weekdays from 8:30am to 6:00pm ET. |
| Additional Information Phone Number | 800 523-1918 |
| Additional Information Website | delawarefunds.com/literature |
| Expenses [Text Block] | What were the Fund's costs for the last 12 months? (Based on a hypothetical $10,000 investment) Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Class C $ 1.50 % |
| Expenses Paid, Amount | $ 156 |
| Expense Ratio, Percent | 1.50% |
| Factors Affecting Performance [Text Block] | Management’s discussion of Fund performance Performance highlights Delaware Tax-Free USA Intermediate Fund (Class C) returned 8.34% (excluding sales charge) for the 12 months ended August 31, 2024. Top contributors to performance: Municipal yields fell over the fiscal year against a backdrop of slowing inflation and anticipation that the US Federal Reserve (Fed) would eventually cut rates. As a result, the longer end of the curve outperformed. Lower-investment-grade and below-investment-grade segments drove performance. The catalyst was a strong technical backdrop of diminutive high yield issuance coupled with inflows to municipal mutual funds, particularly high yield funds. Key contributors to performance included: Out-of-benchmark allocation to the 17+ years segment of the curve relative to the Fund's secondary benchmark Overweight to BBB-rated credit relative to the Fund's primary benchmark Meaningful out-of-benchmark allocation to below-investment-grade securities relative to the Fund's benchmarks Top detractors from performance: The front end of the curve – which is, by its nature, shorter in duration – detracted from performance over the fiscal year, as this maturity segment lagged relative to the intermediate and long ends of the curve. Key detractors from performance relative to the Fund's secondary benchmark included: Modest out-of-benchmark allocation to the front end (0-1 year) of the curve Allocation to pre-refunded bonds, predominantly on the front end of the curve |
| Performance Past Does Not Indicate Future [Text] | Keep in mind that the Fund's past performance is not a good predictor of how the Fund will perform in the future. |
| Line Graph [Table Text Block] | Fund performance The following graph compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years of the Class. It also assumes a $10,000 initial investment at the beginning of the first full fiscal year in a broad-based Growth of $10,000 investment For the period August 31, 2014, through August 31, 2024 |
| Average Annual Return [Table Text Block] | Average annual total returns (as of August 31, 2024) 1 year 5 year 10 year Delaware Tax-Free USA Intermediate Fund (Class C) – including sales charge 7.34 % 0.48 % 1.37 % Delaware Tax-Free USA Intermediate Fund (Class C) – excluding sales charge 8.34 % 0.48 % 1.37 % Bloomberg Municipal Bond Index 6.09 % 1.02 % 2.43 % Bloomberg 3–15 Year Blend Municipal Bond Index 5.26 % 1.10 % 2.25 % |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. |
| Performance Table Market Index Changed [Text Block] | In connection with new regulatory requirements, effective the date of this report, the Fund changed its broad-based securities market benchmark index to the Bloomberg Municipal Bond Index. Although the Bloomberg Municipal Bond Index can be considered broadly representative of the overall securities market applicable to the Fund, the Fund will continue to show the performance of the Bloomberg 3–15 Year Blend Municipal Bond Index for comparative purposes because the Delaware Management Company, the Fund's manager, believes it is more representative of the Fund’s investment universe. |
| Updated Performance Information Location [Text Block] | Visit delawarefunds.com/performance for the most recent performance information. |
| Net Assets | $ 1,213,278,557 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 4,204,145 |
| Investment Company Portfolio Turnover | 28% |
| Additional Fund Statistics [Text Block] | Fund statistics Fund net assets $ Total number of portfolio holdings 453 Total advisory fees paid $ Portfolio turnover rate 28 % |
| Holdings [Text Block] | Fund holdings The tables below show the investment makeup of the Fund, with each category representing a percentage of the total net assets of the Fund. Sector allocation Industrial Development Revenue/Pollution Control 19.18 % Transportation Revenue Bonds 16.10 % Special Tax Revenue Bonds 13.80 % State General Obligation Bonds 9.90 % Lease Revenue Bonds 8.45 % Healthcare Revenue Bonds 8.15 % Education Revenue Bonds 6.82 % Local General Obligation Bonds 4.86 % Electric Revenue Bonds 4.20 % Housing Revenue Bonds 4.13 % State and territory allocation New York 15.15 % Puerto Rico 10.67 % California 10.24 % Illinois 9.74 % Florida 6.21 % New Jersey 5.31 % Colorado 4.37 % Arizona 4.01 % Pennsylvania 3.49 % Texas 3.12 % |
| C000074147 [Member] | |
| Shareholder Report [Line Items] | |
| Fund Name | Delaware Tax-Free USA Intermediate Fund |
| Class Name | Institutional Class |
| Trading Symbol | DUSIX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Delaware Tax-Free USA Intermediate Fund (Fund) for the period of September 1, 2023, to August 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at delawarefunds.com/literature. You can also request this information by contacting us at 800 523-1918, weekdays from 8:30am to 6:00pm ET. |
| Additional Information Phone Number | 800 523-1918 |
| Additional Information Website | delawarefunds.com/literature |
| Expenses [Text Block] | What were the Fund's costs for the last 12 months? (Based on a hypothetical $10,000 investment) Class Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Institutional Class $ 0.50 % |
| Expenses Paid, Amount | $ 52 |
| Expense Ratio, Percent | 0.50% |
| Factors Affecting Performance [Text Block] | Management’s discussion of Fund performance Performance highlights Delaware Tax-Free USA Intermediate Fund (Institutional Class) returned 9.37% (excluding sales charge) for the 12 months ended August 31, 2024. Top contributors to performance: Municipal yields fell over the fiscal year against a backdrop of slowing inflation and anticipation that the US Federal Reserve (Fed) would eventually cut rates. As a result, the longer end of the curve outperformed. Lower-investment-grade and below-investment-grade segments drove performance. The catalyst was a strong technical backdrop of diminutive high yield issuance coupled with inflows to municipal mutual funds, particularly high yield funds. Key contributors to performance included: Out-of-benchmark allocation to the 17+ years segment of the curve relative to the Fund's secondary benchmark Overweight to BBB-rated credit relative to the Fund's primary benchmark Meaningful out-of-benchmark allocation to below-investment-grade securities relative to the Fund's benchmarks Top detractors from performance: The front end of the curve – which is, by its nature, shorter in duration – detracted from performance over the fiscal year, as this maturity segment lagged relative to the intermediate and long ends of the curve. Key detractors from performance relative to the Fund's secondary benchmark included: Modest out-of-benchmark allocation to the front end (0-1 year) of the curve Allocation to pre-refunded bonds, predominantly on the front end of the curve |
| Performance Past Does Not Indicate Future [Text] | Keep in mind that the Fund's past performance is not a good predictor of how the Fund will perform in the future. |
| Line Graph [Table Text Block] | Fund performance The following graph compares the initial and subsequent account values at the end of each of the most recently completed 10 fiscal years of the Class. It also assumes a $10,000 initial investment at the beginning of the first full fiscal year in a broad-based Growth of $10,000 investment For the period August 31, 2014, through August 31, 2024 |
| Average Annual Return [Table Text Block] | Average annual total returns (as of August 31, 2024) 1 year 5 year 10 year Delaware Tax-Free USA Intermediate Fund (Institutional Class) – including sales charge 9.37 % 1.47 % 2.38 % Delaware Tax-Free USA Intermediate Fund (Institutional Class) – excluding sales charge 9.37 % 1.47 % 2.38 % Bloomberg Municipal Bond Index 6.09 % 1.02 % 2.43 % Bloomberg 3–15 Year Blend Municipal Bond Index 5.26 % 1.10 % 2.25 % |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares. |
| Performance Table Market Index Changed [Text Block] | In connection with new regulatory requirements, effective the date of this report, the Fund changed its broad-based securities market benchmark index to the Bloomberg Municipal Bond Index. Although the Bloomberg Municipal Bond Index can be considered broadly representative of the overall securities market applicable to the Fund, the Fund will continue to show the performance of the Bloomberg 3–15 Year Blend Municipal Bond Index for comparative purposes because the Delaware Management Company, the Fund's manager, believes it is more representative of the Fund’s investment universe. |
| Updated Performance Information Location [Text Block] | Visit delawarefunds.com/performance for the most recent performance information. |
| Net Assets | $ 1,213,278,557 |
| Holdings Count | Holding | 453 |
| Advisory Fees Paid, Amount | $ 4,204,145 |
| Investment Company Portfolio Turnover | 28% |
| Additional Fund Statistics [Text Block] | Fund statistics Fund net assets $ Total number of portfolio holdings 453 Total advisory fees paid $ Portfolio turnover rate 28 % |
| Holdings [Text Block] | Fund holdings The tables below show the investment makeup of the Fund, with each category representing a percentage of the total net assets of the Fund. Sector allocation Industrial Development Revenue/Pollution Control 19.18 % Transportation Revenue Bonds 16.10 % Special Tax Revenue Bonds 13.80 % State General Obligation Bonds 9.90 % Lease Revenue Bonds 8.45 % Healthcare Revenue Bonds 8.15 % Education Revenue Bonds 6.82 % Local General Obligation Bonds 4.86 % Electric Revenue Bonds 4.20 % Housing Revenue Bonds 4.13 % State and territory allocation New York 15.15 % Puerto Rico 10.67 % California 10.24 % Illinois 9.74 % Florida 6.21 % New Jersey 5.31 % Colorado 4.37 % Arizona 4.01 % Pennsylvania 3.49 % Texas 3.12 % |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 120 Months Ended | ||||||||||
| Aug. 31, 2024 | Aug. 31, 2024 | Aug. 31, 2024 | Aug. 31, 2023 | Aug. 31, 2022 | Aug. 31, 2021 | Aug. 31, 2020 | Aug. 31, 2019 | Aug. 31, 2018 | Aug. 31, 2017 | Aug. 31, 2016 | Aug. 31, 2015 | Aug. 31, 2014 | |
| C000006385 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Fund (Class A) – including sales charge | ||||||||||||
| Account Value | $ 12,734 | $ 12,734 | $ 12,734 | $ 11,371 | $ 11,453 | $ 13,112 | $ 12,017 | $ 11,616 | $ 10,719 | $ 10,567 | $ 10,526 | $ 9,836 | $ 9,550 |
| Average Annual Return, Percent | 6.97% | 0.91% | 2.45% | ||||||||||
| C000006385 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Fund (Class A) – excluding sales charge | ||||||||||||
| Average Annual Return, Percent | 11.99% | 1.84% | 2.92% | ||||||||||
| C000006387 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Fund (Class C) – including sales charge | ||||||||||||
| Account Value | $ 12,356 | $ 12,356 | $ 12,356 | 11,116 | 11,281 | 13,013 | 12,018 | 11,706 | 10,884 | 10,811 | 10,850 | 10,214 | 10,000 |
| Average Annual Return, Percent | 10.15% | 1.08% | 2.14% | ||||||||||
| C000006387 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Fund (Class C) – excluding sales charge | ||||||||||||
| Average Annual Return, Percent | 11.15% | 1.08% | 2.14% | ||||||||||
| C000074146 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Fund (Institutional Class) – including sales charge | ||||||||||||
| Account Value | $ 13,660 | $ 13,660 | $ 13,660 | 12,174 | 12,227 | 13,969 | 12,766 | 12,310 | 11,326 | 11,146 | 11,072 | 10,315 | 10,000 |
| Average Annual Return, Percent | 12.21% | 2.09% | 3.17% | ||||||||||
| C000074146 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Fund (Institutional Class) – excluding sales charge | ||||||||||||
| Average Annual Return, Percent | 12.21% | 2.09% | 3.17% | ||||||||||
| C000006388 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Intermediate Fund (Class A) – including sales charge | ||||||||||||
| Account Value | $ 12,090 | $ 12,090 | $ 12,090 | 11,076 | 11,058 | 12,331 | 11,649 | 11,335 | 10,522 | 10,463 | 10,427 | 9,855 | 9,725 |
| Average Annual Return, Percent | 6.17% | 0.72% | 1.92% | ||||||||||
| C000006388 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Intermediate Fund (Class A) – excluding sales charge | ||||||||||||
| Average Annual Return, Percent | 9.15% | 1.28% | 2.20% | ||||||||||
| C000006390 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Intermediate Fund (Class C) – including sales charge | ||||||||||||
| Account Value | $ 11,453 | $ 11,453 | $ 11,453 | 10,572 | 10,634 | 11,953 | 11,390 | 11,178 | 10,464 | 10,494 | 10,548 | 10,054 | 10,000 |
| Average Annual Return, Percent | 7.34% | 0.48% | 1.37% | ||||||||||
| C000006390 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Intermediate Fund (Class C) – excluding sales charge | ||||||||||||
| Average Annual Return, Percent | 8.34% | 0.48% | 1.37% | ||||||||||
| C000074147 [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Intermediate Fund (Institutional Class) – including sales charge | ||||||||||||
| Account Value | $ 12,646 | $ 12,646 | $ 12,646 | 11,562 | 11,511 | 12,814 | 12,090 | 11,746 | 10,883 | 10,803 | 10,756 | 10,153 | 10,000 |
| Average Annual Return, Percent | 9.37% | 1.47% | 2.38% | ||||||||||
| C000074147 [Member] | Without Sales Load [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Delaware Tax-Free USA Intermediate Fund (Institutional Class) – excluding sales charge | ||||||||||||
| Average Annual Return, Percent | 9.37% | 1.47% | 2.38% | ||||||||||
| Bloomberg Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg Municipal Bond Index | ||||||||||||
| Account Value | $ 12,708 | $ 12,708 | $ 12,708 | 11,979 | 11,778 | 12,891 | 12,468 | 12,077 | 11,108 | 11,054 | 10,958 | 10,252 | 10,000 |
| Average Annual Return, Percent | 6.09% | 1.02% | 2.43% | ||||||||||
| Bloomberg 3 15 Year Blend Municipal Bond Index [Member] | |||||||||||||
| Account Value [Line Items] | |||||||||||||
| Line Graph and Table Measure Name | Bloomberg 3–15 Year Blend Municipal Bond Index | ||||||||||||
| Account Value | $ 12,492 | $ 12,492 | $ 12,492 | $ 11,868 | $ 11,672 | $ 12,563 | $ 12,227 | $ 11,826 | $ 10,934 | $ 10,929 | $ 10,811 | $ 10,202 | $ 10,000 |
| Average Annual Return, Percent | 5.26% | 1.10% | 2.25% |
| Shareholder Report, Holdings (Details) | Aug. 31, 2024 |
| C000006385 [Member] | PUERTO RICO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.87% |
| C000006385 [Member] | ARIZONA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.65% |
| C000006385 [Member] | CALIFORNIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.91% |
| C000006385 [Member] | COLORADO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.49% |
| C000006385 [Member] | FLORIDA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.84% |
| C000006385 [Member] | ILLINOIS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.21% |
| C000006385 [Member] | NEW YORK | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.86% |
| C000006385 [Member] | OHIO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.77% |
| C000006385 [Member] | PENNSYLVANIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.84% |
| C000006385 [Member] | TEXAS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.98% |
| C000006385 [Member] | Special Tax Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.49% |
| C000006385 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.91% |
| C000006385 [Member] | Healthcare Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.75% |
| C000006385 [Member] | Education Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.24% |
| C000006385 [Member] | Transportation Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| C000006385 [Member] | Lease Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.31% |
| C000006385 [Member] | State General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.39% |
| C000006385 [Member] | Housing Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.31% |
| C000006385 [Member] | Local General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| C000006385 [Member] | Electric Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.19% |
| C000006387 [Member] | PUERTO RICO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.87% |
| C000006387 [Member] | ARIZONA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.65% |
| C000006387 [Member] | CALIFORNIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.91% |
| C000006387 [Member] | COLORADO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.49% |
| C000006387 [Member] | FLORIDA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.84% |
| C000006387 [Member] | ILLINOIS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.21% |
| C000006387 [Member] | NEW YORK | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.86% |
| C000006387 [Member] | OHIO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.77% |
| C000006387 [Member] | PENNSYLVANIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.84% |
| C000006387 [Member] | TEXAS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.98% |
| C000006387 [Member] | Special Tax Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.49% |
| C000006387 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.91% |
| C000006387 [Member] | Healthcare Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.75% |
| C000006387 [Member] | Education Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.24% |
| C000006387 [Member] | Transportation Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| C000006387 [Member] | Lease Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.31% |
| C000006387 [Member] | State General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.39% |
| C000006387 [Member] | Housing Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.31% |
| C000006387 [Member] | Local General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| C000006387 [Member] | Electric Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.19% |
| C000074146 [Member] | PUERTO RICO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.87% |
| C000074146 [Member] | ARIZONA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.65% |
| C000074146 [Member] | CALIFORNIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.91% |
| C000074146 [Member] | COLORADO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.49% |
| C000074146 [Member] | FLORIDA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.84% |
| C000074146 [Member] | ILLINOIS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.21% |
| C000074146 [Member] | NEW YORK | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.86% |
| C000074146 [Member] | OHIO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.77% |
| C000074146 [Member] | PENNSYLVANIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.84% |
| C000074146 [Member] | TEXAS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.98% |
| C000074146 [Member] | Special Tax Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.49% |
| C000074146 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.91% |
| C000074146 [Member] | Healthcare Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.75% |
| C000074146 [Member] | Education Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.24% |
| C000074146 [Member] | Transportation Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| C000074146 [Member] | Lease Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.31% |
| C000074146 [Member] | State General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.39% |
| C000074146 [Member] | Housing Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.31% |
| C000074146 [Member] | Local General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| C000074146 [Member] | Electric Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.19% |
| C000006388 [Member] | PUERTO RICO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.67% |
| C000006388 [Member] | ARIZONA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.01% |
| C000006388 [Member] | CALIFORNIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.24% |
| C000006388 [Member] | COLORADO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.37% |
| C000006388 [Member] | FLORIDA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.21% |
| C000006388 [Member] | ILLINOIS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.74% |
| C000006388 [Member] | NEW JERSEY | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.31% |
| C000006388 [Member] | NEW YORK | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.15% |
| C000006388 [Member] | PENNSYLVANIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.49% |
| C000006388 [Member] | TEXAS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.12% |
| C000006388 [Member] | Special Tax Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.80% |
| C000006388 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.18% |
| C000006388 [Member] | Healthcare Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.15% |
| C000006388 [Member] | Education Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.82% |
| C000006388 [Member] | Transportation Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.10% |
| C000006388 [Member] | Lease Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.45% |
| C000006388 [Member] | State General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.90% |
| C000006388 [Member] | Housing Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.13% |
| C000006388 [Member] | Local General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.86% |
| C000006388 [Member] | Electric Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| C000006390 [Member] | PUERTO RICO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.67% |
| C000006390 [Member] | ARIZONA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.01% |
| C000006390 [Member] | CALIFORNIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.24% |
| C000006390 [Member] | COLORADO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.37% |
| C000006390 [Member] | FLORIDA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.21% |
| C000006390 [Member] | ILLINOIS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.74% |
| C000006390 [Member] | NEW JERSEY | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.31% |
| C000006390 [Member] | NEW YORK | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.15% |
| C000006390 [Member] | PENNSYLVANIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.49% |
| C000006390 [Member] | TEXAS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.12% |
| C000006390 [Member] | Special Tax Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.80% |
| C000006390 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.18% |
| C000006390 [Member] | Healthcare Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.15% |
| C000006390 [Member] | Education Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.82% |
| C000006390 [Member] | Transportation Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.10% |
| C000006390 [Member] | Lease Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.45% |
| C000006390 [Member] | State General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.90% |
| C000006390 [Member] | Housing Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.13% |
| C000006390 [Member] | Local General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.86% |
| C000006390 [Member] | Electric Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| C000074147 [Member] | PUERTO RICO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.67% |
| C000074147 [Member] | ARIZONA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.01% |
| C000074147 [Member] | CALIFORNIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.24% |
| C000074147 [Member] | COLORADO | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.37% |
| C000074147 [Member] | FLORIDA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.21% |
| C000074147 [Member] | ILLINOIS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.74% |
| C000074147 [Member] | NEW JERSEY | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.31% |
| C000074147 [Member] | NEW YORK | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.15% |
| C000074147 [Member] | PENNSYLVANIA | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.49% |
| C000074147 [Member] | TEXAS | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.12% |
| C000074147 [Member] | Special Tax Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.80% |
| C000074147 [Member] | Industrial Development Revenue Pollution Control Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 19.18% |
| C000074147 [Member] | Healthcare Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.15% |
| C000074147 [Member] | Education Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.82% |
| C000074147 [Member] | Transportation Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.10% |
| C000074147 [Member] | Lease Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.45% |
| C000074147 [Member] | State General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.90% |
| C000074147 [Member] | Housing Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.13% |
| C000074147 [Member] | Local General Obligation Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.86% |
| C000074147 [Member] | Electric Revenue Bonds [Member] | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
