Shareholder Report, Holdings (Details)	Aug. 31, 2026
C000005541 \| Virginia
Holdings [Line Items]
Percent of Net Asset Value	79.90%
C000005541 \| District of Columbia
Holdings [Line Items]
Percent of Net Asset Value	13.50%
C000005541 \| Puerto Rico
Holdings [Line Items]
Percent of Net Asset Value	5.60%
C000005541 \| Investment TypeOther Holdings Grouping
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000005541 \| Hospital Revenue
Holdings [Line Items]
Percent of Net Asset Value	21.50%
C000005541 \| Ground Transportation Revenue
Holdings [Line Items]
Percent of Net Asset Value	21.30%
C000005541 \| Educational Revenue
Holdings [Line Items]
Percent of Net Asset Value	10.90%
C000005541 \| Housing Finance Revenue
Holdings [Line Items]
Percent of Net Asset Value	9.60%
C000005541 \| Dedicated Tax Revenue
Holdings [Line Items]
Percent of Net Asset Value	9.30%
C000005541 \| Lease Revenue
Holdings [Line Items]
Percent of Net Asset Value	8.30%
C000005541 \| General Obligations - Local
Holdings [Line Items]
Percent of Net Asset Value	6.80%
C000005541 \| Water & Sewer Revenue
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000005541 \| General Obligations - State
Holdings [Line Items]
Percent of Net Asset Value	1.90%
C000005541 \| Other 2
Holdings [Line Items]
Percent of Net Asset Value	5.40%
C000193180 \| Virginia
Holdings [Line Items]
Percent of Net Asset Value	79.90%
C000193180 \| District of Columbia
Holdings [Line Items]
Percent of Net Asset Value	13.50%
C000193180 \| Puerto Rico
Holdings [Line Items]
Percent of Net Asset Value	5.60%
C000193180 \| Investment TypeOther Holdings Grouping
Holdings [Line Items]
Percent of Net Asset Value	1.00%
C000193180 \| Hospital Revenue
Holdings [Line Items]
Percent of Net Asset Value	21.50%
C000193180 \| Ground Transportation Revenue
Holdings [Line Items]
Percent of Net Asset Value	21.30%
C000193180 \| Educational Revenue
Holdings [Line Items]
Percent of Net Asset Value	10.90%
C000193180 \| Housing Finance Revenue
Holdings [Line Items]
Percent of Net Asset Value	9.60%
C000193180 \| Dedicated Tax Revenue
Holdings [Line Items]
Percent of Net Asset Value	9.30%
C000193180 \| Lease Revenue
Holdings [Line Items]
Percent of Net Asset Value	8.30%
C000193180 \| General Obligations - Local
Holdings [Line Items]
Percent of Net Asset Value	6.80%
C000193180 \| Water & Sewer Revenue
Holdings [Line Items]
Percent of Net Asset Value	5.00%
C000193180 \| General Obligations - State
Holdings [Line Items]
Percent of Net Asset Value	1.90%
C000193180 \| Other 2
Holdings [Line Items]
Percent of Net Asset Value	5.40%