v3.26.1
Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended
Mar. 31, 2026
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Eaton Vance National Ultra-Short Municipal Income Fund | Eaton Vance National Ultra-Short Municipal Income Fund | Bloomberg Municipal Bond Index (reflects no deduction for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent   4.25% 0.80% 2.34%
Eaton Vance National Ultra-Short Municipal Income Fund | Eaton Vance National Ultra-Short Municipal Income Fund | Bloomberg 1 Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent   3.47% 1.73% 1.58%
Eaton Vance National Ultra-Short Municipal Income Fund | Eaton Vance National Ultra-Short Municipal Income Fund | Advisers Class        
Prospectus [Line Items]        
Average Annual Return, Percent   3.14% 1.99% 1.48%
Performance Inception Date Nov. 20, 2020      
Eaton Vance National Ultra-Short Municipal Income Fund | Eaton Vance National Ultra-Short Municipal Income Fund | Class A        
Prospectus [Line Items]        
Average Annual Return, Percent   0.76% 1.51% 1.24%
Eaton Vance National Ultra-Short Municipal Income Fund | Eaton Vance National Ultra-Short Municipal Income Fund | Class A | Return After Taxes on Distributions        
Prospectus [Line Items]        
Average Annual Return, Percent   0.74% 1.49% 1.23%
Eaton Vance National Ultra-Short Municipal Income Fund | Eaton Vance National Ultra-Short Municipal Income Fund | Class A | Return After Taxes on Distributions and Sale of Fund Shares        
Prospectus [Line Items]        
Average Annual Return, Percent   1.60% 1.61% 1.29%
Eaton Vance National Ultra-Short Municipal Income Fund | Eaton Vance National Ultra-Short Municipal Income Fund | Class I        
Prospectus [Line Items]        
Average Annual Return, Percent   3.30% 2.15% 1.64%
Eaton Vance National Limited Maturity Municipal Income Fund | Eaton Vance National Limited Maturity Municipal Income Fund | Bloomberg Municipal Bond Index (reflects no deduction for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent   4.25% 0.80% 2.34%
Eaton Vance National Limited Maturity Municipal Income Fund | Eaton Vance National Limited Maturity Municipal Income Fund | Bloomberg Short-Intermediate 1-10 Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent   5.01% 1.22% 1.98%
Eaton Vance National Limited Maturity Municipal Income Fund | Eaton Vance National Limited Maturity Municipal Income Fund | Class A        
Prospectus [Line Items]        
Average Annual Return, Percent   0.77% 0.77% 1.59%
Eaton Vance National Limited Maturity Municipal Income Fund | Eaton Vance National Limited Maturity Municipal Income Fund | Class A | Return After Taxes on Distributions        
Prospectus [Line Items]        
Average Annual Return, Percent   0.67% 0.67% 1.52%
Eaton Vance National Limited Maturity Municipal Income Fund | Eaton Vance National Limited Maturity Municipal Income Fund | Class A | Return After Taxes on Distributions and Sale of Fund Shares        
Prospectus [Line Items]        
Average Annual Return, Percent   1.63% 1.07% 1.75%
Eaton Vance National Limited Maturity Municipal Income Fund | Eaton Vance National Limited Maturity Municipal Income Fund | Class C        
Prospectus [Line Items]        
Average Annual Return, Percent   2.29% 0.68% 1.17%
Eaton Vance National Limited Maturity Municipal Income Fund | Eaton Vance National Limited Maturity Municipal Income Fund | Class I        
Prospectus [Line Items]        
Average Annual Return, Percent   4.40% 1.61% 2.09%
Eaton Vance Short Duration Municipal Opportunities Fund | Eaton Vance Short Duration Municipal Opportunities Fund | Bloomberg Municipal Bond Index (reflects no deduction for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent   4.25% 0.80% 2.34%
Eaton Vance Short Duration Municipal Opportunities Fund | Eaton Vance Short Duration Municipal Opportunities Fund | Bloomberg Short-Intermediate 1-10 Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes)        
Prospectus [Line Items]        
Average Annual Return, Percent   5.01% 1.22% 1.98%
Eaton Vance Short Duration Municipal Opportunities Fund | Eaton Vance Short Duration Municipal Opportunities Fund | Class A        
Prospectus [Line Items]        
Average Annual Return, Percent   1.41% 1.19% 1.93%
Eaton Vance Short Duration Municipal Opportunities Fund | Eaton Vance Short Duration Municipal Opportunities Fund | Class A | Return After Taxes on Distributions        
Prospectus [Line Items]        
Average Annual Return, Percent   1.22% 1.08% 1.84%
Eaton Vance Short Duration Municipal Opportunities Fund | Eaton Vance Short Duration Municipal Opportunities Fund | Class A | Return After Taxes on Distributions and Sale of Fund Shares        
Prospectus [Line Items]        
Average Annual Return, Percent   1.89% 1.33% 1.90%
Eaton Vance Short Duration Municipal Opportunities Fund | Eaton Vance Short Duration Municipal Opportunities Fund | Class C        
Prospectus [Line Items]        
Average Annual Return, Percent   3.10% 1.11% 1.51%
Eaton Vance Short Duration Municipal Opportunities Fund | Eaton Vance Short Duration Municipal Opportunities Fund | Class I        
Prospectus [Line Items]        
Average Annual Return, Percent   4.96% 2.01% 2.42%