Shareholder Report, Line Graph (Details) - USD ($) |
3 Months Ended | 6 Months Ended | 9 Months Ended | 12 Months Ended | 15 Months Ended | 18 Months Ended | 21 Months Ended | 24 Months Ended | 27 Months Ended | 30 Months Ended | 33 Months Ended | 36 Months Ended | 39 Months Ended | 42 Months Ended | 45 Months Ended | 48 Months Ended | 51 Months Ended | 54 Months Ended | 57 Months Ended | 60 Months Ended | 63 Months Ended | 66 Months Ended | 69 Months Ended | 72 Months Ended | 75 Months Ended | 78 Months Ended | 81 Months Ended | 84 Months Ended | 87 Months Ended | 90 Months Ended | 93 Months Ended | 96 Months Ended | 99 Months Ended | 102 Months Ended | 105 Months Ended | 108 Months Ended | 111 Months Ended | 114 Months Ended | 117 Months Ended | 120 Months Ended | ||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Aug. 31, 2016 |
Nov. 30, 2016 |
Feb. 28, 2017 |
May 31, 2017 |
Aug. 31, 2026 |
Aug. 31, 2017 |
Nov. 30, 2017 |
Feb. 28, 2018 |
May 31, 2018 |
Aug. 31, 2018 |
Nov. 30, 2018 |
Feb. 28, 2019 |
May 31, 2019 |
Aug. 31, 2019 |
Nov. 30, 2019 |
Feb. 29, 2020 |
May 31, 2020 |
Aug. 31, 2020 |
Nov. 30, 2020 |
Feb. 28, 2021 |
May 31, 2021 |
Aug. 31, 2021 |
Nov. 30, 2021 |
Feb. 28, 2022 |
May 31, 2022 |
Aug. 31, 2022 |
Nov. 30, 2022 |
Feb. 28, 2023 |
May 31, 2023 |
Aug. 31, 2023 |
Nov. 30, 2023 |
Feb. 29, 2024 |
May 31, 2024 |
Aug. 31, 2024 |
Nov. 30, 2024 |
Feb. 28, 2025 |
May 31, 2025 |
Aug. 31, 2025 |
Nov. 30, 2025 |
Feb. 28, 2026 |
May 31, 2026 |
Aug. 31, 2026 |
|
| C000007079 | ||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Investor Shares | |||||||||||||||||||||||||||||||||||||||||
| Accumulated Value | $ 10,000 | $ 10,015 | $ 10,032 | $ 10,052 | $ 10,072 | $ 10,094 | $ 10,123 | $ 10,160 | $ 10,193 | $ 10,233 | $ 10,272 | $ 10,315 | $ 10,354 | $ 10,387 | $ 10,417 | $ 10,448 | $ 10,452 | $ 10,454 | $ 10,456 | $ 10,457 | $ 10,458 | $ 10,459 | $ 10,461 | $ 10,471 | $ 10,499 | $ 10,545 | $ 10,618 | $ 10,699 | $ 10,791 | $ 10,888 | $ 10,974 | $ 11,070 | $ 11,160 | $ 11,251 | $ 11,318 | $ 11,404 | $ 11,476 | $ 11,555 | $ 11,616 | $ 11,690 | $ 11,761 | |
| NACC2 Index: Bloomberg Municipal Bond Index | ||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Bloomberg Municipal Bond Index | |||||||||||||||||||||||||||||||||||||||||
| Accumulated Value | 10,000 | 9,479 | 9,720 | 9,968 | 10,088 | 10,008 | 9,963 | 10,079 | 10,138 | 10,121 | 10,375 | 10,724 | 11,022 | 10,980 | 11,356 | 11,151 | 11,378 | 11,518 | 11,476 | 11,679 | 11,765 | 11,745 | 11,401 | 10,885 | 10,749 | 10,730 | 10,819 | 10,939 | 10,932 | 11,189 | 11,406 | 11,231 | 11,598 | 11,741 | 11,743 | 11,459 | 11,607 | 12,050 | 12,326 | 12,223 | 12,085 | |
| NACC2 Index: Short Municipal Debt Funds Average | ||||||||||||||||||||||||||||||||||||||||||
| Account Value [Line Items] | ||||||||||||||||||||||||||||||||||||||||||
| Line Graph and Table Measure Name | Short Municipal Debt Funds Average | |||||||||||||||||||||||||||||||||||||||||
| Accumulated Value | $ 10,000 | $ 9,887 | $ 9,964 | $ 10,019 | $ 10,067 | $ 10,012 | $ 10,032 | $ 10,056 | $ 10,104 | $ 10,113 | $ 10,214 | $ 10,307 | $ 10,405 | $ 10,416 | $ 10,512 | $ 10,470 | $ 10,565 | $ 10,597 | $ 10,608 | $ 10,645 | $ 10,660 | $ 10,634 | $ 10,505 | $ 10,388 | $ 10,369 | $ 10,388 | $ 10,429 | $ 10,495 | $ 10,567 | $ 10,697 | $ 10,813 | $ 10,829 | $ 11,040 | $ 11,110 | $ 11,196 | $ 11,227 | $ 11,391 | $ 11,472 | $ 11,618 | $ 11,613 | $ 11,657 | |