| Form N-CSR Cover | 6 Months Ended |
| May 31, 2024 | |
| 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 | May 31, 2024 |
| Shareholder Report | 6 Months Ended | |
| May 31, 2024 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 | May 31, 2024 | |
| Class A | ||
| Shareholder Report [Line Items] | ||
| Fund Name | ClearBridge Large Cap Growth Fund | |
| Class Name | Class A | |
| Trading Symbol | SBLGX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| 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 $10,000 investment Costs paid as a percentage of a $10,000 investment †, * Class A $55 1.02% | [1],[2] |
| Expenses Paid, Amount | $ 55 | |
| Expense Ratio, Percent | 1.02% | |
| Net Assets | $ 11,000,391,203 | |
| Holdings Count | $ / shares | 44 | [3] |
| Investment Company Portfolio Turnover | 6% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Total Net Assets $11,000,391,203 Total Number of Portfolio Holdings * 44 Portfolio Turnover Rate 6% | [3] |
| Holdings [Text Block] | ||
| Class C | ||
| Shareholder Report [Line Items] | ||
| Fund Name | ClearBridge Large Cap Growth Fund | |
| Class Name | Class C | |
| Trading Symbol | SLCCX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| 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 $10,000 investment Costs paid as a percentage of a $10,000 investment †, * Class C $93 1.73% | [4],[5] |
| Expenses Paid, Amount | $ 93 | |
| Expense Ratio, Percent | 1.73% | |
| Net Assets | $ 11,000,391,203 | |
| Holdings Count | $ / shares | 44 | [6] |
| Investment Company Portfolio Turnover | 6% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Total Net Assets $11,000,391,203 Total Number of Portfolio Holdings * 44 Portfolio Turnover Rate 6% | [6] |
| Holdings [Text Block] | ||
| Class I | ||
| Shareholder Report [Line Items] | ||
| Fund Name | ClearBridge Large Cap Growth Fund | |
| Class Name | Class I | |
| Trading Symbol | SBLYX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| 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 $10,000 investment Costs paid as a percentage of a $10,000 investment †, * Class I $40 0.73% | [7],[8] |
| Expenses Paid, Amount | $ 40 | |
| Expense Ratio, Percent | 0.73% | |
| Net Assets | $ 11,000,391,203 | |
| Holdings Count | $ / shares | 44 | [9] |
| Investment Company Portfolio Turnover | 6% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Total Net Assets $11,000,391,203 Total Number of Portfolio Holdings * 44 Portfolio Turnover Rate 6% | [9] |
| Holdings [Text Block] | ||
| Class IS | ||
| Shareholder Report [Line Items] | ||
| Fund Name | ClearBridge Large Cap Growth Fund | |
| Class Name | Class IS | |
| Trading Symbol | LSITX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| 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 $10,000 investment Costs paid as a percentage of a $10,000 investment †, * Class IS $35 0.64% | [10],[11] |
| Expenses Paid, Amount | $ 35 | |
| Expense Ratio, Percent | 0.64% | |
| Net Assets | $ 11,000,391,203 | |
| Holdings Count | $ / shares | 44 | [12] |
| Investment Company Portfolio Turnover | 6% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Total Net Assets $11,000,391,203 Total Number of Portfolio Holdings * 44 Portfolio Turnover Rate 6% | [12] |
| Holdings [Text Block] | ||
| Class O | ||
| Shareholder Report [Line Items] | ||
| Fund Name | ClearBridge Large Cap Growth Fund | |
| Class Name | Class O | |
| Trading Symbol | LCMMX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| 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 $10,000 investment Costs paid as a percentage of a $10,000 investment †, * Class O $37 0.68% | [13],[14] |
| Expenses Paid, Amount | $ 37 | |
| Expense Ratio, Percent | 0.68% | |
| Net Assets | $ 11,000,391,203 | |
| Holdings Count | $ / shares | 44 | [15] |
| Investment Company Portfolio Turnover | 6% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Total Net Assets $11,000,391,203 Total Number of Portfolio Holdings * 44 Portfolio Turnover Rate 6% | [15] |
| Holdings [Text Block] | ||
| Class R | ||
| Shareholder Report [Line Items] | ||
| Fund Name | ClearBridge Large Cap Growth Fund | |
| Class Name | Class R | |
| Trading Symbol | LMPLX | |
| Shareholder Report Annual or Semi-Annual | semi-annual shareholder report | |
| 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 $10,000 investment Costs paid as a percentage of a $10,000 investment †, * Class R $72 1.33% | [16],[17] |
| Expenses Paid, Amount | $ 72 | |
| Expense Ratio, Percent | 1.33% | |
| Net Assets | $ 11,000,391,203 | |
| Holdings Count | $ / shares | 44 | [18] |
| Investment Company Portfolio Turnover | 6% | |
| Additional Fund Statistics [Text Block] | KEY FUND STATISTICS (as of May 31, 2024) Total Net Assets $11,000,391,203 Total Number of Portfolio Holdings * 44 Portfolio Turnover Rate 6% | [18] |
| Holdings [Text Block] | ||
| [1] * Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. † Annualized. * Does not include derivatives, except purchased option contracts, if any. * Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. † Annualized. * Does not include derivatives, except purchased option contracts, if any. * Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. † Annualized. * Does not include derivatives, except purchased option contracts, if any. * Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. † Annualized. * Does not include derivatives, except purchased option contracts, if any. * Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. † Annualized. * Does not include derivatives, except purchased option contracts, if any. * Reflects fee waivers and/or expense reimbursements, without which expenses would have been higher. † Annualized. * Does not include derivatives, except purchased option contracts, if any. | ||
| Shareholder Report, Holdings (Details) | May 31, 2024 |
| Class A | Information Technology [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.20% |
| Class A | Health Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.70% |
| Class A | Communication Services [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class A | Industrials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class A | Financials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.80% |
| Class A | Consumer Discretionary [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.40% |
| Class A | Consumer Staples [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| Class A | Real Estate [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.80% |
| Class A | Materials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.70% |
| Class A | Utilities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| Class A | Short-Term Investments [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| Class C | Information Technology [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.20% |
| Class C | Health Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.70% |
| Class C | Communication Services [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class C | Industrials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class C | Financials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.80% |
| Class C | Consumer Discretionary [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.40% |
| Class C | Consumer Staples [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| Class C | Real Estate [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.80% |
| Class C | Materials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.70% |
| Class C | Utilities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| Class C | Short-Term Investments [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| Class I | Information Technology [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.20% |
| Class I | Health Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.70% |
| Class I | Communication Services [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class I | Industrials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class I | Financials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.80% |
| Class I | Consumer Discretionary [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.40% |
| Class I | Consumer Staples [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| Class I | Real Estate [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.80% |
| Class I | Materials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.70% |
| Class I | Utilities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| Class I | Short-Term Investments [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| Class IS | Information Technology [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.20% |
| Class IS | Health Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.70% |
| Class IS | Communication Services [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class IS | Industrials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class IS | Financials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.80% |
| Class IS | Consumer Discretionary [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.40% |
| Class IS | Consumer Staples [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| Class IS | Real Estate [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.80% |
| Class IS | Materials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.70% |
| Class IS | Utilities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| Class IS | Short-Term Investments [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| Class O | Information Technology [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.20% |
| Class O | Health Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.70% |
| Class O | Communication Services [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class O | Industrials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class O | Financials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.80% |
| Class O | Consumer Discretionary [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.40% |
| Class O | Consumer Staples [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| Class O | Real Estate [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.80% |
| Class O | Materials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.70% |
| Class O | Utilities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| Class O | Short-Term Investment [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
| Class R | Information Technology [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 35.20% |
| Class R | Health Care [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 14.70% |
| Class R | Communication Services [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class R | Industrials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 10.70% |
| Class R | Financials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.80% |
| Class R | Consumer Discretionary [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 9.40% |
| Class R | Consumer Staples [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 4.10% |
| Class R | Real Estate [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.80% |
| Class R | Materials [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.70% |
| Class R | Utilities [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.20% |
| Class R | Short-Term Investments [Member] | |
| Holdings [Line Items] | |
| Percent of Total Investments | 0.70% |
