v3.26.1
Shareholder Report
 6 Months Ended
Apr. 30, 2026
USD ($)
$ / shares
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Legg Mason Partners Investment Trust
Entity Central Index Key 0000880366
Entity Investment Company Type N-1A
Document Period End Date Apr. 30, 2026
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Class 1  
Shareholder Report [Line Items]  
Fund Name ClearBridge Small Cap Growth Fund
Class Name Class 1
Trading Symbol LMPMX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about ClearBridge Small Cap Growth Fund for the period November 1, 2025, to April 30, 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 877-6LM-FUND/656-3863.
Additional Information Phone Number 877-6LM-FUND/656-3863
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class 1
$47
0.92%
[1],[2]
Expenses Paid, Amount $ 47
Expense Ratio, Percent 0.92%
Net Assets $ 2,001,233,782
Holdings Count | $ / shares 91
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of April 30, 2026)
Total Net Assets
$2,001,233,782
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
91
Portfolio Turnover Rate
12%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of April 30, 2026)
Portfolio Composition* (% of Total Investments)
image
 [3]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class A  
Shareholder Report [Line Items]  
Fund Name ClearBridge Small Cap Growth Fund
Class Name Class A
Trading Symbol SASMX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about ClearBridge Small Cap Growth Fund for the period November 1, 2025, to April 30, 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 877-6LM-FUND/656-3863.
Additional Information Phone Number 877-6LM-FUND/656-3863
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class A
$62
1.21%
[4],[5]
Expenses Paid, Amount $ 62
Expense Ratio, Percent 1.21%
Net Assets $ 2,001,233,782
Holdings Count | $ / shares 91
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of April 30, 2026)
Total Net Assets
$2,001,233,782
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
91
Portfolio Turnover Rate
12%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of April 30, 2026)
Portfolio Composition* (% of Total Investments)
image
 [6]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class C  
Shareholder Report [Line Items]  
Fund Name ClearBridge Small Cap Growth Fund
Class Name Class C
Trading Symbol SCSMX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about ClearBridge Small Cap Growth Fund for the period November 1, 2025, to April 30, 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 877-6LM-FUND/656-3863.
Additional Information Phone Number 877-6LM-FUND/656-3863
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class C
$102
2.00%
[7],[8]
Expenses Paid, Amount $ 102
Expense Ratio, Percent 2.00%
Net Assets $ 2,001,233,782
Holdings Count | $ / shares 91
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of April 30, 2026)
Total Net Assets
$2,001,233,782
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
91
Portfolio Turnover Rate
12%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of April 30, 2026)
Portfolio Composition* (% of Total Investments)
image
 [9]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class FI  
Shareholder Report [Line Items]  
Fund Name ClearBridge Small Cap Growth Fund
Class Name Class FI
Trading Symbol LMPSX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about ClearBridge Small Cap Growth Fund for the period November 1, 2025, to April 30, 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 877-6LM-FUND/656-3863.
Additional Information Phone Number 877-6LM-FUND/656-3863
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class FI
$63
1.24%
[10],[11]
Expenses Paid, Amount $ 63
Expense Ratio, Percent 1.24%
Net Assets $ 2,001,233,782
Holdings Count | $ / shares 91
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of April 30, 2026)
Total Net Assets
$2,001,233,782
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
91
Portfolio Turnover Rate
12%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of April 30, 2026)
Portfolio Composition* (% of Total Investments)
image
 [12]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class R  
Shareholder Report [Line Items]  
Fund Name ClearBridge Small Cap Growth Fund
Class Name Class R
Trading Symbol LMPOX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about ClearBridge Small Cap Growth Fund for the period November 1, 2025, to April 30, 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 877-6LM-FUND/656-3863.
Additional Information Phone Number 877-6LM-FUND/656-3863
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class R
$76
1.49%
[13],[14]
Expenses Paid, Amount $ 76
Expense Ratio, Percent 1.49%
Net Assets $ 2,001,233,782
Holdings Count | $ / shares 91
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of April 30, 2026)
Total Net Assets
$2,001,233,782
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
91
Portfolio Turnover Rate
12%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of April 30, 2026)
Portfolio Composition* (% of Total Investments)
image
 [15]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class I  
Shareholder Report [Line Items]  
Fund Name ClearBridge Small Cap Growth Fund
Class Name Class I
Trading Symbol SBPYX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about ClearBridge Small Cap Growth Fund for the period November 1, 2025, to April 30, 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 877-6LM-FUND/656-3863.
Additional Information Phone Number 877-6LM-FUND/656-3863
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class I
$48
0.93%
[16],[17]
Expenses Paid, Amount $ 48
Expense Ratio, Percent 0.93%
Net Assets $ 2,001,233,782
Holdings Count | $ / shares 91
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of April 30, 2026)
Total Net Assets
$2,001,233,782
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
91
Portfolio Turnover Rate
12%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of April 30, 2026)
Portfolio Composition* (% of Total Investments)
image
 [18]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
Class IS  
Shareholder Report [Line Items]  
Fund Name ClearBridge Small Cap Growth Fund
Class Name Class IS
Trading Symbol LMOIX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about ClearBridge Small Cap Growth Fund for the period November 1, 2025, to April 30, 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 877-6LM-FUND/656-3863.
Additional Information Phone Number 877-6LM-FUND/656-3863
Additional Information Website https://www.franklintempleton.com/regulatory-fund-documents
Expenses [Text Block]
WHAT WERE THE FUND COSTS FOR THE LAST SIX MONTHS? (based on a hypothetical $10,000 investment)
Class Name
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment*,†
Class IS
$40
0.79%
[19],[20]
Expenses Paid, Amount $ 40
Expense Ratio, Percent 0.79%
Net Assets $ 2,001,233,782
Holdings Count | $ / shares 91
Investment Company Portfolio Turnover 12.00%
Additional Fund Statistics [Text Block]
KEY FUND STATISTICS (as of April 30, 2026)
Total Net Assets
$2,001,233,782
Total Number of Portfolio Holdings (excludes derivatives, except purchased options, if any)
91
Portfolio Turnover Rate
12%
Holdings [Text Block]
WHAT DID THE FUND INVEST IN? (as of April 30, 2026)
Portfolio Composition* (% of Total Investments)
image
 [21]
Updated Prospectus Web Address https://www.franklintempleton.com/regulatory-fund-documents
[1]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[2]
† Annualized.
[3]
* Does not include derivatives, except purchased options, if any.  
[4]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[5]
† Annualized.
[6]
* Does not include derivatives, except purchased options, if any.  
[7]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[8]
† Annualized.
[9]
* Does not include derivatives, except purchased options, if any.  
[10]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[11]
† Annualized.
[12]
* Does not include derivatives, except purchased options, if any.  
[13]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[14]
† Annualized.
[15]
* Does not include derivatives, except purchased options, if any.  
[16]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[17]
† Annualized.
[18]
* Does not include derivatives, except purchased options, if any.  
[19]
* Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher.
[20]
† Annualized.
[21]
* Does not include derivatives, except purchased options, if any.