Objective, Primary [Text Block]

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Objective [Heading]

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Investment Objective

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The Global Opportunity Portfolio (the “Fund”) seeks long-term capital appreciation.

Expense [Heading]

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Fees and Expenses

Expense Narrative [Text Block]

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The table below describes the fees and expenses that you may pay if you buy, hold and sell Class IR shares of the Fund. The Fund does not charge any sales loads or other fees when you purchase or redeem Class IR shares. You may pay fees other than the fees and expenses of the Fund, such as brokerage commissions and other fees charged by financial intermediaries, which are not reflected in the tables and examples below.

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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The example below is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The example assumes that you invest $10,000 in the Fund, your investment has a 5% return each year and the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If You SOLD Your Shares

Expense Example, No Redemption, By Year, Caption [Text]

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If You HELD Your Shares

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Total Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 19% of the average value of its portfolio.

Portfolio Turnover, Rate

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19.00%

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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Under normal market conditions, the Adviser seeks to achieve the Fund’s investment objective by investing primarily in established and emerging companies located throughout the world, with capitalizations within the range of companies included in the MSCI All Country World Index.

The Adviser emphasizes a bottom-up stock selection process, seeking attractive investments on an individual company basis. In selecting securities for investment, the Adviser seeks high quality established and emerging companies that the Adviser believes are undervalued at the time of purchase. Fundamental research drives the investment process. The Adviser typically favors companies it believes have sustainable competitive advantages that can be monetized through growth. The investment process integrates analysis of sustainability with respect to disruptive change, financial strength, environmental and social externalities and governance (also referred to as ESG). The Adviser typically focuses a significant portion of the Fund’s investments in a limited number of issuers, which may be in the same industry, sector or geographic region. The Adviser generally considers selling a portfolio holding when it determines that the holding no longer satisfies its investment criteria.

impact the risk and reward profile of investment opportunities, the Adviser typically engages company management in constructive discussions on a range of ESG issues the Adviser deems materially important.

The Fund may invest in China A-Shares (shares of publicly traded companies based in mainland China) listed and traded on the Shanghai Stock Exchange through the Shanghai-Hong Kong Stock Connect program, as well as China A-Shares listed and traded on the Shenzhen-Hong Kong Stock Connect program (collectively, “Stock Connect”).

The Fund may also invest in American Depositary Receipts (“ADRs”), Global Depositary Receipts (“GDRs”) and other types of depositary receipts with respect to issuers located or operating outside of the United States. The Fund may invest in equity securities. The Fund may also invest in privately placed and restricted securities.

Risk [Heading]

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Principal Risks

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s Class IR shares’ performance from year-to-year and by showing how the Fund’s average annual returns for the past one and five year periods and since inception compare with those of a broad measure of market performance. The Fund’s past performance, before and after taxes, is not necessarily an indication of how the Fund will perform in the future. Updated performance information is available online at www.morganstanley.com/im or by calling toll-free 1-800-869-6397.

Performance Information Illustrates Variability of Returns [Text]

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Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-869-6397

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.morganstanley.com/im

Performance Past Does Not Indicate Future [Text]

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The Fund’s past performance, before and after taxes, is not necessarily an indication of how the Fund will perform in the future.

Bar Chart [Heading]

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Annual Total Returns—Calendar Years

Performance Table Uses Highest Federal Rate

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Performance Table Not Relevant to Tax Deferred

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Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and after-tax returns are not relevant to investors who hold their Fund shares through tax deferred arrangements such as 401(k) plans or individual retirement accounts.

Performance Table One Class of after Tax Shown [Text]

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After-tax returns for the Fund’s other classes will vary from Class IR shares’ returns.

Performance Table Explanation after Tax Higher

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After-tax returns may be higher than before-tax returns due to an assumed benefit from capital losses that would have been realized had Fund shares been sold at the end of the relevant periods, as applicable.

Bar Chart Closing [Text Block]

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High Quarter	06/30/20	31.69%
Low Quarter	06/30/22	-27.31%

Performance Table Heading

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Average Annual Total Returns(for the calendar periods ended December 31, 2024)

Performance Table Closing [Text Block]

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The after-tax returns shown in the table above are calculated using the historical highest individual federal marginal income tax rates during the period shown and do not reflect the impact of state and local taxes. After-tax returns for the Fund’s other classes will vary from Class IR shares’ returns. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and after-tax returns are not relevant to investors who hold their Fund shares through tax deferred arrangements such as 401(k) plans or individual retirement accounts. After-tax returns may be higher than before-tax returns due to an assumed benefit from capital losses that would have been realized had Fund shares been sold at the end of the relevant periods, as applicable.

(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Risk Not Insured Depository Institution [Member]

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Risk Lose Money [Member]

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Shares of the Fund are not bank deposits and are not guaranteed or insured by the Federal Deposit Insurance Corporation or any other government agency.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Equity Securities [Member]

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There is no assurance that the Fund will achieve its investment objective, and you can lose money investing in this Fund.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Active Management Risk [Member]

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•

Equity Securities. In general, prices of equity securities are more volatile than those of fixed-income securities. U.S. and foreign stock markets, and equity securities of individual issuers, have experienced periods of substantial price volatility in the past and it is possible that they will do so again in the future. The prices of equity securities fluctuate, sometimes rapidly or widely, in response to activities specific to the issuer of the security as well as factors unrelated to the fundamental condition of the issuer, including general market, economic, political and public health conditions. During periods when equity securities experience heightened volatility, such as during periods of market, economic or financial uncertainty or distress, the Fund’s investments in equity securities are subject to heightened risks.

The value of equity securities declines in response to perceived or actual adverse changes in the economy, economic outlook or financial markets; deterioration in investor sentiment; inflation, interest rate, currency, and commodity price fluctuations; adverse geopolitical, social or environmental developments; issuer- and sector-specific considerations; unexpected trading activity among retail investors; and other factors. Market conditions affect certain types of equity securities to a greater extent than other types of equity securities. If the stock market declines, the value of the Fund’s equity securities will also likely decline, which will result in a decrease in the value of your investment in the Fund. Although prices can rebound, there is no assurance that prices of the Fund’s equity securities will return to previous levels.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Focused Investing [Member]

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•

Active Management Risk. In pursuing the Fund’s investment objective, the Adviser has considerable leeway in deciding which investments to buy, hold or sell on a day-to-day basis, and which trading strategies to use. For example, the Adviser, in its discretion, may determine to use some permitted trading strategies while not using others. The success or failure of such decisions will affect the Fund’s performance.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Foreign and Emerging Market Securities [Member]

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•

Focused Investing. Although the Fund is a diversified investment company under the Investment Company Act of 1940 (the “1940 Act”), the Fund typically invests a significant portion of its portfolio in a limited number of issuers, which may be in the same industry, sector or geographic region. As a result, the Fund will be more susceptible to risks associated with, and negative events affecting those issuers, industries, sectors or geographic regions, and a decline in the value of a particular instrument may cause the Fund’s overall value to be more volatile and decline to a greater degree than if the Fund were invested more widely.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Market and Geopolitical Risk [Member]

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•

after purchase by the Fund, particularly during periods of market, economic, political and social turmoil. When the Fund holds illiquid investments, its portfolio may be harder to value. The risks of investing in emerging market countries are greater than the risks associated with investments in foreign developed countries. Emerging market countries may be subject to increased potential for market manipulation and to less stringent requirements regarding accounting, auditing, financial reporting and record keeping and therefore, material information related to an investment may not be available or reliable. In addition, the Fund is limited in its ability to exercise its legal rights or enforce a counterparty’s legal obligations in certain jurisdictions outside of the United States, in particular, in emerging market countries. In addition, the Fund’s investments in foreign issuers may be denominated in foreign currencies and therefore, to the extent unhedged, the value of those investments will fluctuate with U.S. dollar exchange rates. To the extent hedged by the use of foreign currency forward exchange contracts, the precise matching of the foreign currency forward exchange contract amounts and the value of the securities involved will not generally be possible because the future value of such securities in foreign currencies will change as a consequence of market movements in the value of those securities between the date on which the contract is entered into and the date it matures. There is additional risk that such transactions may reduce or preclude the opportunity for gain if the value of the currency should move in the direction opposite to the position taken and that foreign currency forward exchange contracts create exposure to currencies in which the Fund’s securities are not denominated. The use of foreign currency forward exchange contracts involves the risk of loss from the insolvency or bankruptcy of the counterparty to the contract or the failure of the counterparty to make payments or otherwise comply with the terms of the contract. Economic sanctions or other similar measures may be, and have been, imposed against certain countries, organizations, companies, entities and/or individuals. Economic sanctions and other similar measures could, among other things, effectively restrict or eliminate the Fund’s ability to purchase or sell securities (in the sanctioned country and other markets), negatively impact the value or liquidity of the Fund’s investments, significantly delay or prevent the settlement of the Fund’s securities transactions, force the Fund to sell or otherwise dispose of investments at inopportune times or prices, or impair the Fund’s ability to meet its investment objective or invest in accordance with its investment strategies.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Liquidity [Member]

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•

Market and Geopolitical Risk. The value of your investment in the Fund is based on the values of the Fund’s investments, which change due to economic, geopolitical and other events that affect the U.S. and global markets generally, as well as those that affect or are perceived or expected to affect particular regions, countries, industries, companies, issuers, sectors, asset classes or governments. These types of events may be sudden and unexpected, and could adversely affect the value (or income generated by) and liquidity of the Fund’s investments, which may in turn impact the Fund’s ability to sell securities and/or its ability to meet redemptions. The risks associated with these developments may be magnified if certain social, political, economic and other conditions and events (such as war, natural disasters or events, epidemics and pandemics, terrorism, conflicts, social unrest, recessions, inflation, interest rate changes, supply chain disruptions and the imposition of tariffs, trade barriers and other protectionist or retaliatory measures) adversely interrupt or otherwise affect the global economy and financial markets. It is difficult to predict when events affecting the U.S. or global financial markets or economies may occur, the effects that such events may have and the duration of those effects (which may last for extended periods). These types of events may negatively impact broad segments of businesses and populations and have a significant and rapid negative impact on the performance or value of the Fund’s investments, adversely affect and increase the volatility of the Fund’s share price and exacerbate pre-existing risks to the Fund. The frequency and magnitude of resulting changes in the value of the Fund’s investments cannot be predicted.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Consumer Discretionary/Staples [Member]

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•

Liquidity. The Fund may make investments that are less liquid, illiquid or restricted or that may become illiquid or less liquid in response to overall economic conditions or adverse investor perceptions, and which may entail greater risk than investments in other types of securities. These investments may be more difficult to value or sell, particularly in times of market turmoil, and there may be little trading in the secondary market available for particular securities. If the Fund is forced to sell an illiquid or restricted security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss or for less than its fair value and may be unable to sell the security at all.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Information Technology Sector Risk [Member]

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•

Consumer Discretionary Sector Risk. To the extent that the Fund invests a substantial portion of its assets in the consumer discretionary sector, the Fund will be particularly susceptible to the risks associated with companies operating in such sector(s). Companies in the consumer discretionary sector are subject to risks, including fluctuations in the performance of the overall domestic and international economy, shipment and supply chain disruptions, interest rate changes, currency exchange rates, increased competition and consumer confidence. Performance of such companies may also be adversely affected by factors such as reduced disposable household income, reduced consumer spending, and changing demographics and consumer tastes.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | China Risk [Member]

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•

Information Technology Sector Risk. To the extent the Fund invests a substantial portion of its assets in the information technology sector, the value of Fund shares may be particularly impacted by events that adversely affect the information technology sector, such as rapid changes in technology product cycles, product obsolescence, government regulation, and competition, and may fluctuate more than that of a fund that does not invest significantly in companies in the technology sector.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | India Risk [Member]

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•

the prices at which certain goods may be sold, encouraged companies to invest or concentrate in particular industries, induced mergers between companies in certain industries and induced private companies to publicly offer their securities. Investments in China involve risk of a total loss due to government action or inaction or other adverse circumstances.

Additionally, the Chinese economy is export-driven and highly reliant on trade. Adverse changes to the economic conditions, trading policies and taxation of imports of its primary trading partners, such as the United States, Japan and South Korea, would adversely impact the Chinese economy and the Fund’s investments. Moreover, a slowdown in other significant economies of the world, such as the United States, the European Union and certain Asian countries, may adversely affect economic growth or the value of investments in China. An economic downturn in China would adversely impact the Fund’s investments. In addition, certain securities are, or may in the future, become restricted, and/or sanctioned by the U.S. government or other governments and the Fund may be forced to sell or unable to purchase or sell such restricted securities and incur a loss as a result.

Recent developments in relations between the U.S., other trading partners and China have heightened concerns of increased tariffs and restrictions on trade between the two countries. An increase in tariffs or trade restrictions (and threats thereof) could lead to a significant reduction in international trade, which could have a negative impact on China’s export industry, Chinese issuers, the liquidity or price of the Fund’s direct or indirect investments in China and, therefore, the Fund.

These and other developments, including government actions, may result in significant illiquidity risk or forced disposition for Chinese investments. The Chinese securities markets are emerging markets characterized by a relatively small number of equity issues and relatively low trading volume, resulting in decreased liquidity, greater price volatility (caused by, among other things, military, diplomatic, or trade conflicts), and potentially fewer investment opportunities for the Fund. The Fund’s investments in Chinese securities are also subject to additional risks associated with differing regulatory and audit requirements across the Chinese and U.S. securities markets. Ongoing political tension between the People’s Republic of China and the Hong Kong Special Administrative Region may have impacts on the economy of Hong Kong, and these impacts remain uncertain.

Risks of Investing through Stock Connect. The Fund may invest in A-shares listed and traded through Stock Connect, or on such other stock exchanges in China which participate in Stock Connect from time to time or in the future. Trading through Stock Connect is subject to a number of restrictions that may affect the Fund’s investments and returns. Moreover, Stock Connect A-shares generally may not be sold, purchased or otherwise transferred other than through Stock Connect in accordance with applicable rules. The Stock Connect program is a relatively new program and may be subject to further interpretation and guidance. There can be no assurance as to the program’s continued existence or whether future developments regarding the program may restrict or adversely affect the Fund’s investments or returns. Because certain transactions through Stock Connect may not be subject to certain investor protection programs, the Fund may be exposed to the risks of default of the broker(s) they engage in their trading in China A Shares.

Variable Interest Entities. Chinese operating companies sometimes rely on variable interest entity (“VIE”) structures to raise capital from non-Chinese investors because of Chinese government limitations or prohibitions on direct foreign ownership in certain industries. In a VIE structure, a series of contractual arrangements are entered into between a holding company domiciled outside of China and a Chinese operating company or companies, which are intended to mimic direct ownership in the operating company, but in many cases these arrangements have not been tested in court and it is not clear that the contracts are enforceable or that the structures will otherwise work as intended. The offshore holding company, which is not a Chinese operating company, then issues exchange-traded shares that are sold to the public, including non-Chinese investors (such as the Fund). Shares of the offshore entity purchased by the Fund would not be equity ownership interests in the Chinese operating company and the Fund’s interest would be subject to legal, operational and other risks associated with the company’s use of the VIE structure. For example, at any time the Chinese government could determine that the contractual arrangements constituting part of the VIE structure are unenforceable or do not comply with applicable law or regulations, these laws or regulations could change or be interpreted differently in the future, and the Chinese government may with no advance notice otherwise intervene in or exert influence over VIE structures or the related Chinese operating companies. If any of these or similar risks or developments materialize, the Fund’s investment in the offshore entity may suddenly and significantly decline in value or become worthless because of, among other things, difficulty enforcing (or the inability to enforce) the contractual arrangements or materially adverse effects on the Chinese operating company’s performance. In these circumstances, the Fund could experience significant losses with no recourse available. From time to time, the Fund’s investments in U.S.-listed shell companies relying on VIE structures to consolidate China-based operations could be significant.

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(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | MSCI All Country World Net Index (reflects no deduction for fees, expenses or taxes)

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•

India Risk. To the extent that the Fund invests a substantial portion of its assets in Indian issuers, the value of the Fund’s assets may be adversely affected by political, economic, social and religious factors impacting Indian businesses and the Indian economy, changes in Indian law or regulations and the status of India’s relations with other countries. Indian government actions in the future could have a significant effect on the Indian economy, which could affect private sector companies and the Fund, market conditions, and prices and yields of securities in the Fund’s portfolio. To the extent the Fund invests a significant portion of its assets in Indian businesses and the Indian economy, factors that have an adverse impact on Indian businesses and the Indian economy may have a disproportionate impact on the Fund’s performance.

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rr_AverageAnnualReturnYear01

17.49%

^[1]

rr_AverageAnnualReturnYear05

10.06%

^[1]

(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Class IR

rr_AverageAnnualReturnSinceInception

9.57%

^[1],[2]

Management Fees (as a percentage of Assets)

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rr_ManagementFeesOverAssets

0.74%

^[3]

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.11%

^[4]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.85%

Expense Example, with Redemption, 1 Year

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$ 87

Expense Example, with Redemption, 3 Years

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271

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

471

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,049

Expense Example, No Redemption, 1 Year

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Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

271

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

471

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,049

Annual Return 2019

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35.53%

Annual Return 2020

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55.66%

Annual Return 2021

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0.31%

Annual Return 2022

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(41.51%)

Annual Return 2023

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49.85%

Annual Return 2024

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27.48%

Highest Quarterly Return, Label

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High Quarter

Highest Quarterly Return

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31.69%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2020

Lowest Quarterly Return, Label

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Low Quarter

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(27.31%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2022

rr_AverageAnnualReturnYear01

27.48%

rr_AverageAnnualReturnYear05

11.77%

(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Class IR | Return After Taxes on Distributions

rr_AverageAnnualReturnSinceInception

10.51%

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rr_AverageAnnualReturnYear01

25.04%

^[5]

rr_AverageAnnualReturnYear05

9.90%

^[5]

(MSIF - Opportunity Portfolios - Class IR) | (Global Opportunity Portfolio) | Class IR | Return After Taxes on Distributions and Sale of Fund Shares

rr_AverageAnnualReturnSinceInception

9.06%

^[5]

rr_ProspectusTable

rr_AverageAnnualReturnYear01

18.17%

rr_AverageAnnualReturnYear05

8.96%

(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio)

rr_AverageAnnualReturnSinceInception

8.12%

Objective, Primary [Text Block]

rr_ProspectusTable

Objective [Heading]

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Investment Objective

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The International Opportunity Portfolio (the “Fund”) seeks long-term capital appreciation.

Expense [Heading]

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Fees and Expenses

Expense Narrative [Text Block]

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The table below describes the fees and expenses that you may pay if you buy, hold and sell Class IR shares of the Fund. The Fund does not charge any sales loads or other fees when you purchase Class IR shares. You may pay fees other than the fees and expenses of the Fund, such as brokerage commissions and other fees charged by financial intermediaries, which are not reflected in the tables and examples below.

Shareholder Fees Caption [Text]

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Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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The example below is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The example assumes that you invest $10,000 in the Fund, your investment has a 5% return each year and that the Fund’s operating expenses remain the same (except that the example incorporates the fee waiver and/or expense reimbursement arrangement for only the first year). Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If You SOLD Your Shares

Expense Example, No Redemption, By Year, Caption [Text]

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If You HELD Your Shares

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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Portfolio Turnover, Rate

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28.00%

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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Under normal market conditions, the Adviser seeks to achieve the Fund’s investment objective by investing primarily in established and emerging companies on an international basis, with capitalizations within the range of companies included in the MSCI All Country World ex USA Index.

The Adviser views incorporating ESG-related potential risks and opportunities within the investment process as important to ensure long-term stewardship of capital. Over extended time horizons, the Adviser believes that ESG risks are more likely to materialize and externalities not borne by the company are more likely to be priced into the value of securities. Since ESG risks could potentially impact the risk and reward profile of investment opportunities, the Adviser typically engages company management in constructive discussions on a range of ESG issues the Adviser deems materially important.

The Fund invests primarily in securities of companies located in Europe, Japan, Asia, the Pacific Basin, Latin America, the Middle East and Africa. The Fund may also invest in securities of companies located in the United States to a limited extent.

Risk [Heading]

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Principal Risks

Bar Chart and Performance Table [Heading]

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Performance Information

Performance Narrative [Text Block]

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Performance Information Illustrates Variability of Returns [Text]

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Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-869-6397

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.morganstanley.com/im

Performance Past Does Not Indicate Future [Text]

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The Fund’s past performance, before and after taxes, is not necessarily an indication of how the Fund will perform in the future.

Bar Chart [Heading]

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Annual Total Returns—Calendar Years

Performance Table Uses Highest Federal Rate

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Performance Table Not Relevant to Tax Deferred

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Performance Table One Class of after Tax Shown [Text]

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After-tax returns for the Fund’s other classes will vary from Class IR shares’ returns.

Performance Table Explanation after Tax Higher

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Bar Chart Closing [Text Block]

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High Quarter	06/30/20	34.04%
Low Quarter	03/31/22	-26.32%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns(for the calendar periods ended December 31, 2024)

Performance Table Closing [Text Block]

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Risk Not Insured Depository Institution [Member]

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Risk Lose Money [Member]

rr_RiskTextBlock

Shares of the Fund are not bank deposits and are not guaranteed or insured by the Federal Deposit Insurance Corporation or any other government agency.

rr_ProspectusTable

(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Equity Securities [Member]

rr_RiskTextBlock

There is no assurance that the Fund will achieve its investment objective, and you can lose money investing in this Fund.

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Active Management Risk [Member]

rr_RiskTextBlock

•

rr_ProspectusTable

(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Focused Investing [Member]

rr_RiskTextBlock

•

rr_ProspectusTable

(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Foreign and Emerging Market Securities [Member]

rr_RiskTextBlock

•

events affecting those issuers, industries, sectors or geographic regions, and a decline in the value of a particular instrument may cause the Fund’s overall value to be more volatile and decline to a greater degree than if the Fund were invested more widely.

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Market and Geopolitical Risk [Member]

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Foreign and Emerging Market Securities. Investments in foreign markets entail special risks, such as currency, political (including geopolitical), economic and market risks and heightened risks, that may result in losses to the Fund. There also may be greater market volatility, less reliable financial information, less stringent investor protections and disclosure standards, higher transaction and custody costs and risks, decreased market liquidity and less government and exchange regulation associated with investments in foreign markets. In addition, investments in certain foreign markets that have historically been considered stable may become more volatile and subject to increased risk due to developments and changing conditions in such markets. Moreover, the growing interconnectivity of global economies and financial markets has increased the probability that adverse developments and conditions in one country or region will affect the stability of economies and financial markets in other countries or regions. Certain foreign markets may rely heavily on particular industries or foreign capital and are more vulnerable to diplomatic developments (including regional and global, military, or other conflicts), the imposition of economic sanctions against a particular country or countries, organizations, companies, entities and/or individuals, changes in international trading patterns, trade barriers (including tariffs) and other protectionist or retaliatory measures. Investments in foreign markets may also be adversely affected by governmental interventions or other actions, such as the imposition of capital controls, nationalization of companies or industries, expropriation of assets or the imposition of punitive taxes. The governments of certain countries may prohibit or impose substantial restrictions on foreign investing in their capital markets or in certain sectors or industries. In addition, a foreign government may limit or cause delay in the convertibility or repatriation of its currency which would adversely affect the U.S. dollar value and/or liquidity of investments denominated in that currency. Certain foreign investments may become less liquid and decline in value in response to market developments or adverse investor perceptions, or become illiquid after purchase by the Fund, particularly during periods of market, economic, political and social turmoil. When the Fund holds illiquid investments, its portfolio may be harder to value. The risks of investing in emerging market countries are greater than the risks associated with investments in foreign developed countries. Emerging market countries may be subject to increased potential for market manipulation and to less stringent requirements regarding accounting, auditing, financial reporting and record keeping and therefore, material information related to an investment may not be available or reliable. In addition, the Fund is limited in its ability to exercise its legal rights or enforce a counterparty’s legal obligations in certain jurisdictions outside of the United States, in particular, in emerging market countries. In addition, the Fund’s investments in foreign issuers may be denominated in foreign currencies and therefore, to the extent unhedged, the value of those investments will fluctuate with U.S. dollar exchange rates. To the extent hedged by the use of foreign currency forward exchange contracts, the precise matching of the foreign currency forward exchange contract amounts and the value of the securities involved will not generally be possible because the future value of such securities in foreign currencies will change as a consequence of market movements in the value of those securities between the date on which the contract is entered into and the date it matures. There is additional risk that such transactions may reduce or preclude the opportunity for gain if the value of the currency should move in the direction opposite to the position taken and that foreign currency forward exchange contracts create exposure to currencies in which the Fund’s securities are not denominated. The use of foreign currency forward exchange contracts involves the risk of loss from the insolvency or bankruptcy of the counterparty to the contract or the failure of the counterparty to make payments or otherwise comply with the terms of the contract. Economic sanctions or other similar measures may be, and have been, imposed against certain countries, organizations, companies, entities and/or individuals. Economic sanctions and other similar measures could, among other things, effectively restrict or eliminate the Fund’s ability to purchase or sell securities (in the sanctioned country and other markets), negatively impact the value or liquidity of the Fund’s investments, significantly delay or prevent the settlement of the Fund’s securities transactions, force the Fund to sell or otherwise dispose of investments at inopportune times or prices, or impair the Fund’s ability to meet its investment objective or invest in accordance with its investment strategies.

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Liquidity [Member]

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Consumer Discretionary/Staples [Member]

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•	Liquidity. The Fund may make investments that are less liquid, illiquid or restricted or that may become illiquid or less liquid in response to overall economic conditions or adverse investor perceptions, and which may entail greater risk than investments in

other types of securities. These investments may be more difficult to value or sell, particularly in times of market turmoil, and there may be little trading in the secondary market available for particular securities. If the Fund is forced to sell an illiquid or restricted security to fund redemptions or for other cash needs, it may be forced to sell the security at a loss or for less than its fair value and may be unable to sell the security at all.

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | China Risk [Member]

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Consumer Discretionary Sector Risk. To the extent that the Fund invests a substantial portion of its assets in the consumer discretionary sector, the Fund will be particularly susceptible to the risks associated with companies operating in such sector. Companies in the consumer discretionary sector are subject to risks, including fluctuations in the performance of the overall domestic and international economy, shipment and supply chain disruptions, interest rate changes, currency exchange rates, increased competition and consumer confidence. Performance of such companies may also be adversely affected by factors such as reduced disposable household income, reduced consumer spending, and changing demographics and consumer tastes.

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | India Risk [Member]

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China Risk. Investments in securities of Chinese issuers, including A-shares, involve risks associated with investments in foreign markets as well as special considerations not typically associated with investments in the U.S. securities markets. For example, the Chinese government has historically exercised substantial control over virtually every sector of the Chinese economy through administrative regulation and/or state ownership and actions of the Chinese central and local government authorities continue to have a substantial effect on economic conditions in China. In addition, the Chinese government has taken actions that influenced the prices at which certain goods may be sold, encouraged companies to invest or concentrate in particular industries, induced mergers between companies in certain industries and induced private companies to publicly offer their securities. Investments in China involve risk of a total loss due to government action or inaction or other adverse circumstances.

industries. In a VIE structure, a series of contractual arrangements are entered into between a holding company domiciled outside of China and a Chinese operating company or companies, which are intended to mimic direct ownership in the operating company, but in many cases these arrangements have not been tested in court and it is not clear that the contracts are enforceable or that the structures will otherwise work as intended. The offshore holding company, which is not a Chinese operating company, then issues exchange-traded shares that are sold to the public, including non-Chinese investors (such as the Fund). Shares of the offshore entity purchased by the Fund would not be equity ownership interests in the Chinese operating company and the Fund’s interest would be subject to legal, operational and other risks associated with the company’s use of the VIE structure. For example, at any time the Chinese government could determine that the contractual arrangements constituting part of the VIE structure are unenforceable or do not comply with applicable law or regulations, these laws or regulations could change or be interpreted differently in the future, and the Chinese government may with no advance notice otherwise intervene in or exert influence over VIE structures or the related Chinese operating companies. If any of these or similar risks or developments materialize, the Fund’s investment in the offshore entity may suddenly and significantly decline in value or become worthless because of, among other things, difficulty enforcing (or the inability to enforce) the contractual arrangements or materially adverse effects on the Chinese operating company’s performance. In these circumstances, the Fund could experience significant losses with no recourse available. From time to time, the Fund’s investments in U.S.-listed shell companies relying on VIE structures to consolidate China-based operations could be significant.

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Financials Sector [Member]

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(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | MSCI All Country World ex USA Net Index (reflects no deduction for fees, expenses or taxes)

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Financials Sector Risk. To the extent the Fund invests a substantial portion of its assets in the financials sector, factors that have an adverse impact on this sector may have a disproportionate impact on the Fund’s performance. The financials sector can be affected by global and local economic conditions, such as the levels and liquidity of the global and local financial and asset markets, the absolute and relative level and volatility of interest rates and equity prices, investor sentiment, inflation, and the availability and cost of credit. Adverse developments in these conditions can have a greater adverse effect on the financials sector of an emerging market economy than on other industries of its economy. The enactment of new legislation or regulations, as well as changes in interpretation and enforcement of current laws, may affect the manner of operations and profitability of the financials sector.

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rr_AverageAnnualReturnYear01

5.53%

^[6]

rr_AverageAnnualReturnYear05

4.10%

^[6]

(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Class IR

rr_AverageAnnualReturnSinceInception

4.02%

^[6],[7]

Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price)

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rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum Deferred Sales Charge (as a percentage)

rr_MaximumDeferredSalesChargeOverOther

none

Redemption Fee (as a percentage of Amount Redeemed)

rr_RedemptionFeeOverRedemption

2.00%

Management Fees (as a percentage of Assets)

rr_ManagementFeesOverAssets

0.80%

^[8]

Distribution and Service (12b-1) Fees

rr_DistributionAndService12b1FeesOverAssets

none

Other Expenses (as a percentage of Assets):

rr_OtherExpensesOverAssets

0.15%

^[9]

Total Annual Fund Operating Expenses

rr_ExpensesOverAssets

0.95%

^[10]

Fee Waiver or Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.01%

^[10]

Total Annual Fund Operating Expenses After Expense Reimbursement

rr_NetExpensesOverAssets

0.94%

^[10]

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

$ 96

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

302

Expense Example, with Redemption, 5 Years

rr_ExpenseExampleYear05

525

Expense Example, with Redemption, 10 Years

rr_ExpenseExampleYear10

1,165

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

302

Expense Example, No Redemption, 5 Years

rr_ExpenseExampleNoRedemptionYear05

525

Expense Example, No Redemption, 10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,165

Annual Return 2019

rr_AnnualReturn2019

35.32%

Annual Return 2020

rr_AnnualReturn2020

55.64%

Annual Return 2021

rr_AnnualReturn2021

(5.13%)

Annual Return 2022

rr_AnnualReturn2022

(43.70%)

Annual Return 2023

rr_AnnualReturn2023

21.09%

Annual Return 2024

rr_AnnualReturn2024

19.37%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

High Quarter

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

34.04%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2020

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Low Quarter

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(26.32%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2022

rr_AverageAnnualReturnYear01

19.37%

rr_AverageAnnualReturnYear05

3.74%

(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Class IR | Return After Taxes on Distributions

rr_AverageAnnualReturnSinceInception

3.73%

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rr_AverageAnnualReturnYear01

19.53%

^[11]

rr_AverageAnnualReturnYear05

3.27%

^[11]

(MSIF - Opportunity Portfolios - Class IR) | (International Opportunity Portfolio) | Class IR | Return After Taxes on Distributions and Sale of Fund Shares

rr_AverageAnnualReturnSinceInception

3.36%

^[11]

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rr_AverageAnnualReturnYear01

11.73%

rr_AverageAnnualReturnYear05

2.89%