Eaton Vance National Ultra-Short Municipal Income Fund Eaton Vance National Ultra-Short Municipal Income Fund Eaton Vance National Limited Maturity Municipal Income Fund Eaton Vance National Limited Maturity Municipal Income Fund Eaton Vance Short Duration Municipal Opportunities Fund Eaton Vance Short Duration Municipal Opportunities Fund Deatonvancenationalultrashortmunicipalincomefundprospectus_17568 Eaton Vance National Ultra-Short Municipal Income Fund Deatonvancenationallimitedmaturitymunicipalincomefundprospectus_17571 Eaton Vance National Limited Maturity Municipal Income Fund Deatonvanceshortdurationmunicipalopportunitiesfundprospectus_17558 Eaton Vance Short Duration Municipal Opportunities Fund Deatonvancenationalultrashortmunicipalincomefundsai_17567 Eaton Vance National Ultra-Short Municipal Income Fund SAI Deatonvancenationallimitedmaturitymunicipalincomefundsai_17572 Eaton Vance National Limited Maturity Municipal Income Fund SAI Deatonvanceshortdurationmunicipalopportunitiesfundsai_17560 Eaton Vance Short Duration Municipal Opportunities Fund SAI Class Advisor - C000225142 Advisers Class Class A - C000013046 Class A Class I - C000091009 Class I Class A - C000013052 Class A Class C - C000013054 Class C Class I - C000081647 Class I Class A - C000013049 Class A Class C - C000013051 Class C Class I - C000091010 Class I Market Risk_1 Market Risk [Member] Municipal Obligations Risk [Member] Municipal Obligations Risk [Member] Interest Rate Risk [Member] Interest Rate Risk [Member] Credit Risk [Member] Credit Risk [Member] Lower Rated Investments Risk [Member] Lower Rated Investments Risk [Member] Derivatives Risk [Member] Derivatives Risk [Member] Leverage Risk [Member] Leverage Risk [Member] Risk of Residual Interest Bonds [Member] Risk of Residual Interest Bonds [Member] Restricted Securities Risk [Member] Restricted Securities Risk [Member] Tax-Sensitive Investing Risk [Member] Tax-Sensitive Investing Risk [Member] Liquidity Risk [Member] Liquidity Risk [Member] Risks of Principal Only Investments [Member] Risks of Principal Only Investments [Member] Pooled Investment Vehicles Risk [Member] Pooled Investment Vehicles Risk [Member] U.S. Government Securities Risk [Member] U.S. Government Securities Risk [Member] Tax Risk [Member] Tax Risk [Member] Portfolio Turnover Risk [Member] Portfolio Turnover Risk [Member] Risks Associated with Active Management [Member] Risks Associated with Active Management [Member] Sector and Geographic Risk [Member] Sector and Geographic Risk [Member] General Fund Investing Risks [Member] General Fund Investing Risks [Member] Return After Taxes on Distributions Return After Taxes on Distributions Return After Taxes on Distributions and Sale of Fund Shares Return After Taxes on Distributions and Sale of Fund Shares Bloomberg Municipal Bond Index (reflects no deduction for fees, expenses or taxes) Bloomberg Municipal Bond Index (reflects no deduction for fees, expenses or taxes) Bloomberg 1 Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes) Bloomberg 1 Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes) Market Risk [Member] Market Risk [Member] Bloomberg Short-Intermediate 1-10 Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes) Bloomberg Short-Intermediate 1-10 Year Municipal Bond Index (reflects no deduction for fees, expenses or taxes)