v3.26.1
Shareholder Report
6 Months Ended
May 31, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name First Trust Exchange-Traded Fund VIII
Entity Central Index Key 0001667919
Entity Investment Company Type N-1A
Document Period End Date May 31, 2026
C000243906 [Member]  
Shareholder Report [Line Items]  
Fund Name First Trust Active Global Quality Income ETF
Class Name First Trust Active Global Quality Income ETF
Trading Symbol AGQI
Security Exchange Name NYSEArca
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the First Trust Active Global Quality Income ETF (the “Fund”) for the period of December 1, 2025 to May 31, 2026.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at www.ftportfolios.com/fund-documents/etf/AGQI. You can also request this information by contacting us at 1-800-621-1675 or info@ftportfolios.com.
Additional Information Phone Number 1-800-621-1675
Additional Information Email info@ftportfolios.com
Additional Information Website www.ftportfolios.com/fund-documents/etf/AGQI
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS?
(Based on a hypothetical $10,000 investment)
Fund Costs of a $10,000 investment Costs paid as a percentage
of a $10,000 investment
First Trust Active Global Quality Income ETF $45 0.85%(1)
(1)
Annualized.
Expenses Paid, Amount $ 45
Expense Ratio, Percent 0.85% [1]
Net Assets $ 55,960,555
Holdings Count | Holding 33
Investment Company Portfolio Turnover 40.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (As of May 31, 2026)
Fund net assets $55,960,555
Total number of portfolio holdings 33
Portfolio turnover rate 40%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (As of May 31, 2026)
The tables below show the investment makeup of the Fund, representing the percentage of total investments of the Fund.
Top Ten Holdings
Microsoft Corp. 5.2%
Taiwan Semiconductor Manufacturing Co., Ltd. 4.8%
Alphabet, Inc., Class C 4.3%
Chevron Corp. 4.2%
Samsung Electronics Co., Ltd. 4.2%
Carlsberg A/S, Class B 4.0%
BAE Systems PLC 3.8%
Rio Tinto PLC 3.7%
Tokyo Electron Ltd. 3.5%
Coca-Cola (The) Co. 3.5%
Sector Allocation
Graphical Representation - Allocation 2 Chart
Largest Holdings [Text Block]
Top Ten Holdings
Microsoft Corp. 5.2%
Taiwan Semiconductor Manufacturing Co., Ltd. 4.8%
Alphabet, Inc., Class C 4.3%
Chevron Corp. 4.2%
Samsung Electronics Co., Ltd. 4.2%
Carlsberg A/S, Class B 4.0%
BAE Systems PLC 3.8%
Rio Tinto PLC 3.7%
Tokyo Electron Ltd. 3.5%
Coca-Cola (The) Co. 3.5%
C000247844 [Member]  
Shareholder Report [Line Items]  
Fund Name FT Energy Income Partners Enhanced Income ETF
Class Name FT Energy Income Partners Enhanced Income ETF
Trading Symbol EIPI
Security Exchange Name NYSEArca
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the FT Energy Income Partners Enhanced Income ETF (the “Fund”) for the period of December 1, 2025 to May 31, 2026.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at www.ftportfolios.com/fund-documents/etf/EIPI. You can also request this information by contacting us at 1-800-621-1675 or info@ftportfolios.com.
Additional Information Phone Number 1-800-621-1675
Additional Information Email info@ftportfolios.com
Additional Information Website www.ftportfolios.com/fund-documents/etf/EIPI
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS?
(Based on a hypothetical $10,000 investment)
Fund Costs of a $10,000 investment Costs paid as a percentage
of a $10,000 investment
FT Energy Income Partners Enhanced Income ETF $58(1) 1.10%(1) (2)
(1)
Excludes any Acquired Fund Fees and Expenses of the underlying investment companies in which the Fund invests.
(2)
Annualized.
Expenses Paid, Amount $ 58 [2]
Expense Ratio, Percent 1.10% [2],[3]
Net Assets $ 1,052,418,750
Holdings Count | Holding 126
Investment Company Portfolio Turnover 74.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (As of May 31, 2026)
Fund net assets $1,052,418,750
Total number of portfolio holdings 126
Portfolio turnover rate 74%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (As of May 31, 2026)
The tables below show the investment makeup of the Fund, representing the percentage of total investments of the Fund.
Top Ten Holdings
Enterprise Products Partners, L.P. 7.9%
Energy Transfer, L.P. 6.5%
MPLX, L.P. 4.4%
Kinder Morgan, Inc. 3.9%
Williams (The) Cos., Inc. 3.1%
ONEOK, Inc. 2.8%
National Fuel Gas Co. 2.5%
Duke Energy Corp. 2.4%
Morgan Stanley Institutional Liquidity Funds - Treasury Portfolio - Institutional Class 2.4%
Shell PLC, ADR 2.4%
Sector Allocation
Graphical Representation - Allocation 2 Chart
Largest Holdings [Text Block]
Top Ten Holdings
Enterprise Products Partners, L.P. 7.9%
Energy Transfer, L.P. 6.5%
MPLX, L.P. 4.4%
Kinder Morgan, Inc. 3.9%
Williams (The) Cos., Inc. 3.1%
ONEOK, Inc. 2.8%
National Fuel Gas Co. 2.5%
Duke Energy Corp. 2.4%
Morgan Stanley Institutional Liquidity Funds - Treasury Portfolio - Institutional Class 2.4%
Shell PLC, ADR 2.4%
C000257285 [Member]  
Shareholder Report [Line Items]  
Fund Name FT Confluence BDC & Specialty Finance Income ETF
Class Name FT Confluence BDC & Specialty Finance Income ETF
Trading Symbol FBDC
Security Exchange Name NYSEArca
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the FT Confluence BDC & Specialty Finance Income ETF (the “Fund”) for the period of December 1, 2025 to May 31, 2026.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at www.ftportfolios.com/fund-documents/etf/FBDC. You can also request this information by contacting us at 1-800-621-1675 or info@ftportfolios.com.
Additional Information Phone Number 1-800-621-1675
Additional Information Email info@ftportfolios.com
Additional Information Website www.ftportfolios.com/fund-documents/etf/FBDC
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS?
(Based on a hypothetical $10,000 investment)
Fund Costs of a $10,000 investment Costs paid as a percentage
of a $10,000 investment
FT Confluence BDC & Specialty Finance Income ETF $46(1) 0.95%(1) (2)
(1)
Excludes any Acquired Fund Fees and Expenses of the underlying investment companies in which the Fund invests.
(2)
Annualized.
Expenses Paid, Amount $ 46 [4]
Expense Ratio, Percent 0.95% [4],[5]
Net Assets $ 34,302,782
Holdings Count | Holding 21
Investment Company Portfolio Turnover 5.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (As of May 31, 2026)
Fund net assets $34,302,782
Total number of portfolio holdings 21
Portfolio turnover rate 5%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (As of May 31, 2026)
The tables below show the investment makeup of the Fund, representing the percentage of total investments of the Fund.
Top Ten Holdings
Main Street Capital Corp. 11.5%
Ares Capital Corp. 10.6%
Hercules Capital, Inc. 10.3%
Golub Capital BDC, Inc. 9.6%
Blackstone Secured Lending Fund 8.1%
Sixth Street Specialty Lending, Inc. 7.9%
Blue Owl Capital Corp. 6.6%
Barings BDC, Inc. 5.1%
New Mountain Finance Corp. 4.6%
Capital Southwest Corp. 4.5%
Industry Allocation
Graphical Representation - Allocation 2 Chart
Largest Holdings [Text Block]
Top Ten Holdings
Main Street Capital Corp. 11.5%
Ares Capital Corp. 10.6%
Hercules Capital, Inc. 10.3%
Golub Capital BDC, Inc. 9.6%
Blackstone Secured Lending Fund 8.1%
Sixth Street Specialty Lending, Inc. 7.9%
Blue Owl Capital Corp. 6.6%
Barings BDC, Inc. 5.1%
New Mountain Finance Corp. 4.6%
Capital Southwest Corp. 4.5%
[1]
Annualized.
[2]
Excludes any Acquired Fund Fees and Expenses of the underlying investment companies in which the Fund invests.
[3]
Annualized.
[4] Excludes any Acquired Fund Fees and Expenses of the underlying investment companies in which the Fund invests.
[5] Annualized.