Gabelli Growth Innovators ETF Early Closetrading Halt Risk [Member] Authorized Participant Concentration Risk [Member] Large Shareholder Risk [Member] Absence Of An Active Market [Member] Equity Risk [Member] American Depositary Receipts A D Rs Risk [Member] Foreign Securities Risk [Member] Growth Stock Risk [Member] Issuer Risk [Member] Inflation Risk [Member] Market Risk [Member] Management Risk [Member] Market Trading Risk [Member] Technology Sector Risk [Member] Preferred Stock Risk [Member] Trading Issues Risk [Member] Geopolitical Risk [Member] Gabelli Love Our Planet & People ETF Sector Risk [Member] Socially Responsible Investment Risk [Member] Gabelli Global Technology Leaders ETF Concentration Risk [Member] Risk Of Investing In Japan [Member] Risk Of Investing In Europe [Member] Risk Of Investing In United Kingdom [Member] Large Capitalization Companies Risk [Member] Small And Midcapitalization Companies Risk [Member] Nondiversification Risk [Member] Options Risk [Member] Absence Of Active Market [Member] Gabelli Commercial Aerospace and Defense ETF Aerospace Industry Risk [Member] Defense Industry Risk [Member] Value Investing Risk [Member] Gabelli Financial Services Opportunities ETF Gabelli Financial Services Opportunities ETF New Fund Risk [Member] Risk Of Investing In The United Kingdom [Member] Financial Services Risk [Member] Infectious Illness Risk [Member] Gabelli High Income ETF Credits Risk [Member] Debt Instruments Risk [Member] Lowerrated Debt Securities Risk [Member] Unrated Fixed Income Securities Risk [Member] Collateralized Debt Obligations Risk [Member] Interests Rate Risk [Member] Bank Loan Risk [Member] Convertible Securities Risk [Member] Counterparty Risk [Member] Prepayment And Extension Risk [Member] Call Risk [Member] Restricted And Illiquid Securities Risk [Member] Loan Interests Risk [Member] Variable And Floating Rate Instruments Risk [Member] Highly Leveraged Transactions Risk [Member] Impairment Of Collateral Risk [Member] Distressed Securities Risk [Member] Deferred Payment Securities Risk [Member] Paymentinkind Securities Risk [Member] Emerging Markets Risk [Member] Currency Risk [Member] Changing Distribution Level Risk [Member] Derivatives Risk [Member] Short-Term Investments [Member] U S Government Securities [Member] Other Investment Company Risk [Member] Keeley Dividend ETF Dividendpaying Securities Risk [Member] Gabelli Opportunities in Live and Sports ETF Communication Services Risk [Member] Professional Sports Risk [Member] Gabelli Equity Income ETF Non Transparent Exchange Traded Fund E T F Structure Risk [Member] Authorized Participant And A P Representative Concentration Risk [Member] Gabelli Small & Mid Cap ETF Mid Capitalization Company Risk [Member] Small Capitalization Company Risk [Member] Gabelli Micro Cap ETF Micro Cap Company Risk [Member] Gabelli Green Energy ETF Clean Energy Company Risk [Member] Gabelli Growth Innovators ETF Gabelli Love Our Planet & People ETF Gabelli Global Technology Leaders ETF Gabelli Commercial Aerospace and Defense ETF Gabelli High Income ETF Keeley Dividend ETF Gabelli Opportunities in Live and Sports ETF Gabelli Equity Income ETF Gabelli Small & Mid Cap ETF Gabelli Micro Cap ETF Gabelli Green Energy ETF Risks Nondiversified Status [Member] S&P 500 Financials Index S&P 500 Index Nasdaq Composite Index (reflects no deduction for fees, expenses or taxes) Gabelli Financial Services Opportunities ETF [Default Label] Gabelli Growth Innovators ETF [Default Label] Gabelli Love Our Planet & People ETF [Default Label] Gabelli Global Technology Leaders ETF [Default Label] Gabelli Commercial Aerospace and Defense ETF [Default Label] Gabelli High Income ETF [Default Label] Keeley Dividend ETF [Default Label] Gabelli Opportunities in Live and Sports ETF [Default Label] Gabelli Equity Income ETF [Default Label] Gabelli Small & Mid Cap ETF [Default Label] Gabelli Micro Cap ETF [Default Label] Gabelli Green Energy ETF [Default Label]