110001 - Disclosure - First Trust AAA CMBS ETF Investment Objectives and Goals link:presentationLink link:definitionLink link:calculationLink 110002 - Disclosure - First Trust AAA CMBS ETF Fees and Expenses link:presentationLink link:definitionLink link:calculationLink 110003 - Disclosure - First Trust AAA CMBS ETF Investment Strategy link:presentationLink link:definitionLink link:calculationLink 110004 - Disclosure - First Trust AAA CMBS ETF Investment Risks link:presentationLink link:definitionLink link:calculationLink 110005 - Disclosure - First Trust AAA CMBS ETF Performance Management link:presentationLink link:definitionLink link:calculationLink 120010 - Disclosure - First Trust AAA CMBS ETF Shareholder Fees link:presentationLink link:definitionLink link:calculationLink 120020 - Disclosure - First Trust AAA CMBS ETF Annual Fund Operating Expenses link:presentationLink link:definitionLink link:calculationLink 120030 - Disclosure - First Trust AAA CMBS ETF Expense Example link:presentationLink link:definitionLink link:calculationLink 120040 - Disclosure - First Trust AAA CMBS ETF Expense Example, No Redemption link:presentationLink link:definitionLink link:calculationLink 120045 - Disclosure - First Trust AAA CMBS ETF Risks Data link:presentationLink link:definitionLink link:calculationLink 120050 - Disclosure - First Trust AAA CMBS ETF Annual Total Returns link:presentationLink link:definitionLink link:calculationLink 120060 - Disclosure - First Trust AAA CMBS ETF Average Annual Total Returns link:presentationLink link:definitionLink link:calculationLink 120070 - Disclosure - First Trust AAA CMBS ETF Market Index Performance link:presentationLink link:definitionLink link:calculationLink 110000 - Disclosure - First Trust AAA CMBS ETF N-1A Cover link:presentationLink link:definitionLink link:calculationLink 210001 - Disclosure - First Trust Core Investment Grade ETF Investment Objectives and Goals link:presentationLink link:definitionLink link:calculationLink 210002 - Disclosure - First Trust Core Investment Grade ETF Fees and Expenses link:presentationLink link:definitionLink link:calculationLink 210003 - Disclosure - First Trust Core Investment Grade ETF Investment Strategy link:presentationLink link:definitionLink link:calculationLink 210004 - Disclosure - First Trust Core Investment Grade ETF Investment Risks link:presentationLink link:definitionLink link:calculationLink 210005 - Disclosure - First Trust Core Investment Grade ETF Performance Management link:presentationLink link:definitionLink link:calculationLink 220010 - Disclosure - First Trust Core Investment Grade ETF Shareholder Fees link:presentationLink link:definitionLink link:calculationLink 220020 - Disclosure - First Trust Core Investment Grade ETF Annual Fund Operating Expenses link:presentationLink link:definitionLink link:calculationLink 220030 - Disclosure - First Trust Core Investment Grade ETF Expense Example link:presentationLink link:definitionLink link:calculationLink 220040 - Disclosure - First Trust Core Investment Grade ETF Expense Example, No Redemption link:presentationLink link:definitionLink link:calculationLink 220045 - Disclosure - First Trust Core Investment Grade ETF Risks Data link:presentationLink link:definitionLink link:calculationLink 220050 - Disclosure - First Trust Core Investment Grade ETF Annual Total Returns link:presentationLink link:definitionLink link:calculationLink 220060 - Disclosure - First Trust Core Investment Grade ETF Average Annual Total Returns link:presentationLink link:definitionLink link:calculationLink 220070 - Disclosure - First Trust Core Investment Grade ETF Market Index Performance link:presentationLink link:definitionLink link:calculationLink 210000 - Disclosure - First Trust Core Investment Grade ETF N-1A Cover link:presentationLink link:definitionLink link:calculationLink 310001 - Disclosure - First Trust Structured Credit Income Opportunities ETF Investment Objectives and Goals link:presentationLink link:definitionLink link:calculationLink 310002 - Disclosure - First Trust Structured Credit Income Opportunities ETF Fees and Expenses link:presentationLink link:definitionLink link:calculationLink 310003 - Disclosure - First Trust Structured Credit Income Opportunities ETF Investment Strategy link:presentationLink link:definitionLink link:calculationLink 310004 - Disclosure - First Trust Structured Credit Income Opportunities ETF Investment Risks link:presentationLink link:definitionLink link:calculationLink 310005 - Disclosure - First Trust Structured Credit Income Opportunities ETF Performance Management link:presentationLink link:definitionLink link:calculationLink 320010 - Disclosure - First Trust Structured Credit Income Opportunities ETF Shareholder Fees link:presentationLink link:definitionLink link:calculationLink 320020 - Disclosure - First Trust Structured Credit Income Opportunities ETF Annual Fund Operating Expenses link:presentationLink link:definitionLink link:calculationLink 320030 - Disclosure - First Trust Structured Credit Income Opportunities ETF Expense Example link:presentationLink link:definitionLink link:calculationLink 320040 - Disclosure - First Trust Structured Credit Income Opportunities ETF Expense Example, No Redemption link:presentationLink link:definitionLink link:calculationLink 320045 - Disclosure - First Trust Structured Credit Income Opportunities ETF Risks Data link:presentationLink link:definitionLink link:calculationLink 320050 - Disclosure - First Trust Structured Credit Income Opportunities ETF Annual Total Returns link:presentationLink link:definitionLink link:calculationLink 320060 - Disclosure - First Trust Structured Credit Income Opportunities ETF Average Annual Total Returns link:presentationLink link:definitionLink link:calculationLink 320070 - Disclosure - First Trust Structured Credit Income Opportunities ETF Market Index Performance link:presentationLink link:definitionLink link:calculationLink 310000 - Disclosure - First Trust Structured Credit Income Opportunities ETF N-1A Cover link:presentationLink link:definitionLink link:calculationLink First Trust AAA CMBS ETF S000084026 [Member] C000248162 [Member] Authorized Participant Concentration Risk [Member] Call Risk [Member] Cash Transactions Risk [Member] CMBX Risk [Member] Commercial Mortgage-Backed Securities Risk [Member] Counterparty Risk [Member] Credit Default Swaps Risk [Member] Credit Rating Agency Risk [Member] Credit Risk [Member] Current Market Conditions Risk [Member] Cyber Security Risk [Member] Debt Securities Risk [Member] Derivatives Risk [Member] Extension Risk [Member] Floating Rate Debt Instruments Risk [Member] Forward Contracts Risk [Member] Futures Contracts Risk [Member] Income Risk [Member] Index Or Model Constituent Risk [Member] Inflation Risk [Member] Interest And Principal Only Securities Risk [Member] Interest Rate Risk [Member] Leverage Risk [Member] Liquidity Risk [Member] Management Risk [Member] Market Maker Risk [Member] Market Risk [Member] Non Agency Securities Risk [Member] Risk Nondiversified [Member] Operational Risk [Member] Options Risk [Member] OTC Derivatives Risk [Member] Premium Discount Risk [Member] Prepayment Risk [Member] Restricted Securities Risk [Member] Significant Exposure Risk [Member] Swap Agreements Risk [Member] Trading Issues Risk [Member] Valuation Risk [Member] Volatility Risk [Member] First Trust Core Investment Grade ETF S000082787 [Member] C000246109 [Member] Bloomberg US Aggregate Bond Index (reflects no deduction for fees, expenses or taxes)[Member] ICE BofA US Broad Market Index (reflects no deduction for fees, expenses or taxes)[Member] Alternative Minimum Tax Risk [Member] Asset Backed Securities Risk [Member] CLO Risk [Member] Credit Spread Risk [Member] Emerging Markets Risk [Member] ETF Risk [Member] Floating Rate Securities Risk [Member] Inflation Indexed Securities Risk [Member] Mortgage Related Securities Risk [Member] Municipal Securities Market Liquidity Risk [Member] Municipal Securities Risk [Member] Non US Securities Risk [Member] Portfolio Turnover Risk [Member] Short Sales Risk [Member] Sovereign Debt Securities Risk [Member] US Government Securities Risk [Member] When Issued TBA And Delayed Delivery Transactions Risk [Member] First Trust Structured Credit Income Opportunities ETF S000084090 [Member] C000248350 [Member] Distressed Securities Risk [Member] High Yield Securities Risk [Member] Investment Companies Risk [Member]