v3.26.1
Shareholder Report
 12 Months Ended
Mar. 31, 2026
USD ($)
$ / shares
Shareholder Report [Line Items]  
Document Type N-CSR
Amendment Flag false
Registrant Name Legg Mason ETF Investment Trust
Entity Central Index Key 0001645194
Entity Investment Company Type N-1A
Document Period End Date Mar. 31, 2026
Shareholder Report Annual or Semi-Annual annual shareholder report
Royce Quant Small-Cap Quality Value ETF  
Shareholder Report [Line Items]  
Fund Name Royce Quant Small-Cap Quality Value ETF
Class Name Royce Quant Small-Cap Quality Value ETF
Trading Symbol SQLV
Security Exchange Name NASDAQ
Annual or Semi-Annual Statement [Text Block] This annual shareholder report contains important information about Royce Quant Small-Cap Quality Value ETF for the period April 1, 2025, to March 31, 2026.
Additional Information [Text Block] You can find additional information about the Fund at https://www.franklintempleton.com/regulatory-fund-documents. You can also request this information by contacting us at (800) DIAL BEN/342-5236.
Additional Information Phone Number (800) DIAL BEN/342-5236
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST YEAR? (based on a hypothetical $10,000 investment)
Fund Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Royce Quant Small-Cap Quality Value ETF
$65
0.60%
Expenses Paid, Amount $ 65
Expense Ratio, Percent 0.60%
Factors Affecting Performance [Text Block]
HOW DID THE FUND PERFORM LAST YEAR AND WHAT AFFECTED ITS PERFORMANCE?
For the twelve months ended March 31, 2026, Royce Quant Small-Cap Quality Value ETF returned 18.14%. The Fund compares its performance to the Russell 2000 Index, which returned 25.72% for the same period.
PERFORMANCE HIGHLIGHTS
Top contributors to performance:
↑
Stock selection in the financials and consumer discretionary sectors, as well as an underweight in real estate, contributed most to relative performance.
↑
At the industry level, software (information technology (IT)), insurance (financials), and construction & engineering (industrials) contributed most to relative performance.
↑
At the position level, Argan (industrials), Bel Fuse (IT), and Monte Rosa Therapeutics (health care) contributed most to relative performance.
Top detractors from performance:
↓
Stock selection in the health care, industrials, and communication services sectors detracted most from relative performance.
↓
At the industry level, biotechnology (health care), pharmaceuticals (health care), and metals & mining (materials) detracted most from relative performance.
↓
At the position level, Organon (health care), Accendra Health (health care), and Torrid Holdings (consumer discretionary) detracted most from relative performance.
Performance Past Does Not Indicate Future [Text] The Fund’s past performance is not necessarily an indication of how the Fund will perform in the future.
Line Graph [Table Text Block]
image
Average Annual Return [Table Text Block]
AVERAGE ANNUAL TOTAL RETURNS (%) Period Ended March 31, 2026
 
1 Year
5 Year
Since Inception
(7/12/2017)
Royce Quant Small-Cap Quality Value ETF (NAV)
18.14
5.54
7.96
Russell 3000 Index
18.09
10.87
13.20
Russell 2000 Index
25.72
3.77
8.09
No Deduction of Taxes [Text Block] The graph and table do not reflect the deduction of taxes that a shareholder would pay on Fund distributions or redemption of Fund shares.
Updated Performance Information Location [Text Block]
For current month-end performance, please call Franklin Templeton at (800) DIAL BEN/342-5236 or visit
https://www.franklintempleton.com/investments/options/exchange-traded-funds.
Important data provider notices and terms available at www.franklintempletondatasources.com.
Net Assets $ 24,255,736
Holdings Count | $ / shares 311
Advisory Fees Paid, Amount $ 150,234
Investment Company Portfolio Turnover 57.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of March 31, 2026)
Total Net Assets
$24,255,736
Total Number of Portfolio Holdings
311
Total Management Fee Paid (based on a unitary fee)
$150,234
Portfolio Turnover Rate
57%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of March 31, 2026)
Portfolio Composition* (% of Total Investments)
image
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Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
[1]
* Does not include derivatives, except purchased options, if any.