Objective, Primary [Text Block]

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Objective [Heading]

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Investment Objective

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The Emerging Markets Fixed Income Opportunities Portfolio (the “Fund”) seeks high total return.

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 shares of the Fund. 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.

For purchases of Class A shares, you may qualify for a sales charge discount if the cumulative net asset value per share (“NAV”) of Class A shares of the Fund being purchased in a single transaction, together with the NAV of any Class A, Class L and Class C shares of the Fund already held in Related Accounts (as defined in the section of the Prospectus entitled “Shareholder Information—Sales Charges Applicable to Purchases of Class A Shares”) as of the date of the transaction as well as Class A, Class L and Class C shares of any other Morgan Stanley Multi-Class Fund excluding Morgan Stanley Institutional Fund Trust Short Duration Income, Ultra-Short Income and Ultra-Short Municipal Income Portfolios (as defined in the section of the Prospectus entitled “Shareholder Information—Exchange Privilege”) and including shares of Morgan Stanley Money Market Funds (as defined in the section of the Prospectus entitled “Shareholder Information—Exchange Privilege”) that you acquired in an exchange from Class A, Class L or Class C shares of the Fund or Class A, Class L or Class C shares of another Morgan Stanley Multi-Class Fund excluding Morgan Stanley Institutional Fund Trust Short Duration Income, Ultra-Short Income and Ultra-Short Municipal Income Portfolios already held in Related Accounts as of the date of the transaction, amounts to $100,000 or more. More information about this combined purchase discount and other discounts is available from your authorized financial intermediary, on page 21 of the Prospectus in the section entitled “Shareholder Information—Sales Charges Applicable to Purchases of Class A Shares” and in Appendix A attached to the Prospectus.

Class I shares may be available on brokerage platforms of firms that have agreements with the Fund’s principal underwriter permitting such firms to (i) offer Class I shares solely when acting as an agent for the investor and (ii) impose on an investor transacting in Class I shares through such platforms a commission and/or other forms of compensation to the broker. Shares of the Fund are available in other share classes that have different fees and expenses.

Expense Breakpoint Discounts [Text]

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Expense Breakpoint, Minimum Investment Required [Amount]

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$ 100,000

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 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). After eight years, Class C shares of the Fund generally will convert automatically to Class A shares of the Fund. The example for Class C shares reflects the conversion to Class A shares after eight years. Please refer to the section of the Prospectus entitled “Shareholder Information—Conversion Features” for more information. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

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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 64% of the average value of its portfolio.

Portfolio Turnover, Rate

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64.00%

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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Under normal circumstances, at least 80% of the Fund’s assets will be invested in debt securities of issuers located in emerging market countries, which may include U.S. dollar-denominated, local currency and corporate debt securities. This policy may be changed without shareholder approval; however, you would be notified upon 60 days’ notice in writing of any changes.

The Adviser and/or the “Sub-Advisers,” Morgan Stanley Investment Management Limited (“MSIM Limited”) and Morgan Stanley Investment Management Company (“MSIM Company”) seek high total return by investing primarily in fixed-income securities of government and government-related issuers and corporate issuers in emerging market countries.

The Adviser and/or Sub-Advisers implement a top down assessment of the global economic environment and the sensitivity of emerging economies in general to worldwide events. In selecting the Fund’s investments, the Adviser and/or Sub-Advisers analyze the ability of an emerging market country’s government to formulate and implement fiscal and economic policies; socio-political factors, including political risks, election calendars, human development and social stability; and exchange rate and interest rate valuation.

The Fund’s investment process incorporates information about environmental, social and governance issues (also referred to as ESG) via an integrated approach within the investment team’s fundamental investment analysis framework. The Adviser and/or Sub-Advisers may engage with management of certain issuers regarding corporate governance practices as well as what the Adviser and/or Sub-Advisers deem to be materially important environmental and/or social issues facing a company.

The Fund’s holdings may range in maturity from overnight to 30 years or more and will not be subject to any minimum credit rating standard. The Adviser and/or Sub-Advisers generally consider selling a portfolio holding when it determines that the holding no longer satisfies its investment criteria.

The Fund may invest in fixed-income securities that are rated below “investment grade” or are not rated, but are of equivalent quality. These fixed-income securities are often referred to as “high yield securities” or “junk bonds.” High yield securities are fixed-income securities rated by one or more rating agencies below Baa3 by Moody’s Investors Service, Inc. (“Moody’s”), below BBB- by

S&P Global Ratings Group, a division of S&P Global Inc. (“S&P”), below BBB- by Fitch Ratings Inc. (“Fitch”) or the equivalent by another nationally recognized statistical rating organization (“NRSRO”), or if unrated considered by the Adviser and/or Sub-Advisers to be of equivalent quality.

The Fund may invest in restricted and illiquid securities.

The Fund may, but it is not required to, use derivative instruments for a variety of purposes, including hedging, risk management, portfolio management or to earn income. The Fund’s use of derivatives may involve the purchase and sale of derivative instruments such as futures, options, swaps, structured investments and other related instruments and techniques. The Fund may utilize foreign currency forward exchange contracts, which are also derivatives, in connection with its investments in foreign securities. Derivative instruments used by the Fund will be counted toward the Fund’s 80% policy discussed above to the extent they have economic characteristics similar to the securities included within that policy.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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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. The principal risks of investing in the Fund include:

•

Credit and Interest Rate Risk. Credit risk refers to the possibility that the issuer or guarantor of a security will be unable or unwilling or perceived to be unable or unwilling to make interest payments and/or repay the principal on its debt. In such instances, the value of the Fund could decline and the Fund could lose money. Interest rate risk refers to the decline in the value of a fixed-income security resulting from changes in the general level of interest rates. When the general level of interest rates goes up, the prices of most fixed-income securities go down. When the general level of interest rates goes down, the prices of most fixed-income securities go up. The Fund may face a heightened level of interest rate risk in times of monetary policy change and/or uncertainty, such as when the Federal Reserve Board adjusts a quantitative easing program and/or changes rates. A changing interest rate environment increases certain risks, including the potential for periods of volatility, increased redemptions, shortened durations (i.e., prepayment risk) and extended durations (i.e., extension risk). During periods when interest rates are low or there are negative interest rates, the Fund’s yield (and total return) also may be low or otherwise adversely affected or the Fund may be unable to maintain positive returns. Credit ratings may not be an accurate assessment of liquidity or credit risk. Although credit ratings may not accurately reflect the true credit risk of an instrument, a change in the credit rating of an instrument or an issuer can have a rapid, adverse effect on the instrument’s liquidity and make it more difficult for the Fund to sell at an advantageous price or time.

•

Fixed-Income Securities. Fixed-income securities are subject to the risk of the issuer’s inability to meet principal and interest payments on its obligations (i.e., credit risk) and are subject to price volatility resulting from, among other things, interest rate sensitivity (i.e., interest rate risk), market perception of the creditworthiness of the issuer and general market liquidity (i.e., market risk). The Fund may face a heightened level of interest rate risk in times of monetary policy change and/or uncertainty, such as when the Federal Reserve Board adjusts a quantitative easing program and/or changes rates. A changing interest rate environment increases certain risks, including the potential for periods of volatility, increased redemptions, shortened durations (i.e., prepayment risk) and extended durations (i.e., extension risk). The Fund may be subject to certain liquidity risks that may result from the lack of an active market and the reduced number and capacity of traditional market participants to make a market in fixed-income securities. The Fund is not limited as to the maturities (when a debt security provides its final payment) or durations (measure of interest rate sensitivity) of the securities in which it may invest. Securities with longer durations are likely to be more sensitive to changes in interest rates, generally making them more volatile than securities with shorter durations. Lower rated fixed-income securities have greater volatility because there is less certainty that principal and interest payments will be made as scheduled. Investing in emerging markets intensifies this risk, because lower quality fixed-income securities are more volatile in price.

•

High Yield Securities (“Junk Bonds”). The Fund’s investments in high yield securities expose it to a substantial degree of credit risk. Investing in emerging markets intensifies risk, because high yield securities may be more volatile in price in certain environments. High yield securities may be issued by companies that are restructuring, are smaller and less creditworthy or are more highly indebted than other companies, and therefore they may have more difficulty making scheduled payments of principal and interest. High yield securities are subject to greater risk of loss of income and principal than higher rated securities and may be considered speculative. High yield securities may experience reduced liquidity, and sudden and substantial decreases in price. An economic downturn affecting an issuer of high yield securities may result in an increased incidence of default. In the event of a default, the Fund may incur additional expenses to seek recovery.

•

Foreign and Emerging Market Securities. Investments in foreign markets entail special risks such as currency, political, economic and market risks. There also may be greater market volatility, less reliable financial information, less stringent investor protections and disclosure standards, higher transaction and custody costs, 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 ongoing 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, the imposition of economic sanctions against a particular country or countries, organizations, companies, entities and/or individuals, changes in international trading patterns, trade barriers and other protectionist or retaliatory measures. Investments in foreign markets may also be adversely affected by governmental 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 in response to market developments or adverse investor perceptions, or become illiquid after purchase by the Fund, particularly during periods of market 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. Certain emerging market countries may be subject 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. Certain emerging market or developing countries are among the largest debtors to commercial banks and foreign governments. The issuer or governmental authority that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or pay interest when due in accordance with the terms of such obligations. In addition, foreign governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments. Moreover, there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part. 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 markets 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, 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.

•

Sovereign Debt Securities. Investing in sovereign debt securities will expose the Fund to the direct or indirect consequences of political, social or economic changes in the countries that issue the securities. The issuer or governmental authority that controls the repayment of sovereign debt may not be willing or able to repay the principal and/or pay interest when it becomes due, due to factors such as debt service burden, political constraints, cash flow problems and other national economic factors. In addition, foreign governments may default on their debt securities, which may require holders of such securities to participate in debt rescheduling or additional lending to defaulting governments. Moreover, there is no bankruptcy proceeding by which defaulted sovereign debt may be collected in whole or in part.

•	Leverage. The Fund may borrow money for investment purposes. Borrowing for investment purposes is a speculative activity that creates leverage. Leverage will magnify the effect of increases and decreases in prices of portfolio securities.

•

Liquidity. The Fund may make investments that are illiquid or restricted or that may become 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. Liquidity risk may be magnified in a market where credit spread and interest rate volatility is rising and where investor redemptions from fixed-income mutual funds may be higher than normal. 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.

•

Derivatives. A derivative instrument often has risks similar to its underlying asset and may have additional risks, including imperfect correlation between the value of the derivative and the underlying asset, risks of default by the counterparty to certain transactions, magnification of losses incurred due to changes in the market value of the securities, instruments, indices or interest rates to which the derivative instrument relates, risks that the transactions may not be liquid, risks arising from margin

requirements and risks arising from mispricing or valuation complexity. Certain derivative transactions may give rise to a form of leverage. Leverage magnifies the potential for gain and the risk of loss.

•

Non-Diversification. The Fund is non-diversified, which means that the Fund may invest a greater percentage of its assets in a smaller number of issuers than a diversified fund. Because the Fund is non-diversified, it may be more susceptible to an adverse event affecting a single issuer or portfolio investment than a diversified portfolio and a decline in the value of that issuer’s securities or that portfolio investment may cause the Fund’s overall value to decline to a greater degree than a diversified portfolio.

•

Market and Geopolitical Risk. The value of your investment in the Fund is based on the values of the Fund’s investments, which may change due to economic and other events that affect markets generally, as well as those that affect particular regions, countries, industries, companies or governments. These events may be sudden and unexpected, and could adversely affect the liquidity of the Fund’s investments, which may in turn impact valuation, 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, epidemics and pandemics, terrorism, conflicts and social unrest) adversely interrupt the global economy and financial markets. It is difficult to predict when events affecting the U.S. or global financial markets may occur, the effects that such events may have and the duration of those effects (which may last for extended periods). These events may negatively impact broad segments of businesses and populations and have a significant and rapid negative impact on the performance 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.

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.

Risk Lose Money [Text]

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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.

Risk Nondiversified Status [Text]

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Non-Diversification. The Fund is non-diversified, which means that the Fund may invest a greater percentage of its assets in a smaller number of issuers than a diversified fund. Because the Fund is non-diversified, it may be more susceptible to an adverse event affecting a single issuer or portfolio investment than a diversified portfolio and a decline in the value of that issuer’s securities or that portfolio investment may cause the Fund’s overall value to decline to a greater degree than a diversified portfolio.

Risk Not Insured Depository Institution [Text]

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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.

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 the Fund’s Class I 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, as well as an index that represents a group of similar mutual funds, over time. The performance of the other classes, which is shown in the table below, will differ because the classes have different ongoing fees. The Fund’s returns in the table include the maximum applicable sales charge for Class A and Class C and assume you sold your shares at the end of each period (unless otherwise noted). 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 1-800-548-7786.

Performance Information Illustrates Variability of Returns [Text]

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Performance Availability Phone [Text]

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1-800-548-7786

Performance Availability Website Address [Text]

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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 Does Reflect Sales Loads

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The Fund’s returns in the table include the maximum applicable sales charge for Class A and Class C and assume you sold your shares at the end of each period (unless otherwise noted).

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 I shares’ returns.

Performance Table Explanation after Tax Higher

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After-tax returns may be higher than before-tax returns due to foreign tax credits and/or 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

13.16%

Low Quarter

03/31/20

-16.43%

Performance Table Heading

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Average Annual Total Returns(for the calendar periods ended December 31, 2021)

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 I 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 foreign tax credits and/or 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 - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | J.P. Morgan Emerging Markets Blended Index (JEMB) - Equal Weighted (reflects no deduction for fees, expenses or taxes)

rr_ProspectusTable

rr_AverageAnnualReturnYear01

(3.26%)

^[1]

rr_AverageAnnualReturnYear05

4.33%

^[1]

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Emerging Markets Fixed income Blend Index (reflects no deduction for fees, expenses or taxes)

rr_AverageAnnualReturnSinceInception

3.69%

^[1],[2]

rr_ProspectusTable

rr_AverageAnnualReturnYear01

(3.26%)

^[3]

rr_AverageAnnualReturnYear05

4.21%

^[3]

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Lipper Emerging Market Hard Currency Debt Funds Index (reflects no deduction for taxes)

rr_AverageAnnualReturnSinceInception

4.50%

^[2],[3]

rr_ProspectusTable

rr_AverageAnnualReturnYear01

(2.51%)

^[4]

rr_AverageAnnualReturnYear05

3.60%

^[4]

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Class I

rr_AverageAnnualReturnSinceInception

3.74%

^[2],[4]

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

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rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption Fee (as a percentage of Amount Redeemed)

rr_MaximumDeferredSalesChargeOverOther

none

rr_RedemptionFeeOverRedemption

2.00%

rr_ManagementFeesOverAssets

0.75%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

0.96%

rr_ExpensesOverAssets

1.71%

^[5]

Total Annual Fund Operating Expenses After Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.86%

^[5]

rr_NetExpensesOverAssets

0.85%

^[5]

rr_ExpenseExampleYear01

$ 87

rr_ExpenseExampleYear03

455

rr_ExpenseExampleYear05

847

rr_ExpenseExampleYear10

1,948

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

455

rr_ExpenseExampleNoRedemptionYear05

847

Highest Quarterly Return, Label

rr_ExpenseExampleNoRedemptionYear10

$ 1,948

Annual Return 2013

rr_AnnualReturn2013

(8.79%)

Annual Return 2014

rr_AnnualReturn2014

3.38%

Annual Return 2015

rr_AnnualReturn2015

(1.83%)

Annual Return 2016

rr_AnnualReturn2016

12.80%

Annual Return 2017

rr_AnnualReturn2017

12.94%

Annual Return 2018

rr_AnnualReturn2018

(6.93%)

Annual Return 2019

rr_AnnualReturn2019

14.41%

Annual Return 2020

rr_AnnualReturn2020

4.69%

Annual Return 2021

rr_AnnualReturn2021

(3.08%)

rr_HighestQuarterlyReturnLabel

High Quarter

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

13.16%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2020

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Low Quarter

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(16.43%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2020

rr_AverageAnnualReturnYear01

(3.08%)

rr_AverageAnnualReturnYear05

4.06%

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Class I | Return After Taxes on Distributions

rr_AverageAnnualReturnSinceInception

4.04%

rr_ProspectusTable

rr_AverageAnnualReturnYear01

(4.96%)

^[6]

rr_AverageAnnualReturnYear05

1.78%

^[6]

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Class I | Return After Taxes on Distributions and Sale of Fund Shares

rr_AverageAnnualReturnSinceInception

1.65%

^[6]

rr_ProspectusTable

rr_AverageAnnualReturnYear01

(1.82%)

rr_AverageAnnualReturnYear05

2.12%

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Class A

rr_AverageAnnualReturnSinceInception

2.04%

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

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.25%

Redemption Fee (as a percentage of Amount Redeemed)

rr_MaximumDeferredSalesChargeOverOther

none

^[7]

rr_RedemptionFeeOverRedemption

2.00%

rr_ManagementFeesOverAssets

0.75%

rr_DistributionAndService12b1FeesOverAssets

0.25%

rr_OtherExpensesOverAssets

1.06%

rr_ExpensesOverAssets

2.06%

^[5]

Total Annual Fund Operating Expenses After Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.86%

^[5]

rr_NetExpensesOverAssets

1.20%

^[5]

Expenses Deferred Charges [Text Block]

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Investments in Class A shares that are not subject to any sales charges at the time of purchase are subject to a contingent deferred sales charge (“CDSC”) of 0.75% that will be imposed if you sell your shares within 12 months except for certain specific circumstances. See “Shareholder Information—How To Redeem Fund Shares” for further information about the CDSC waiver categories.

rr_ExpenseExampleYear01

$ 443

rr_ExpenseExampleYear03

869

rr_ExpenseExampleYear05

1,321

rr_ExpenseExampleYear10

2,571

rr_ExpenseExampleNoRedemptionYear01

443

rr_ExpenseExampleNoRedemptionYear03

869

rr_ExpenseExampleNoRedemptionYear05

1,321

rr_ExpenseExampleNoRedemptionYear10

$ 2,571

rr_AverageAnnualReturnYear01

(6.59%)

rr_AverageAnnualReturnYear05

3.02%

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Class L

rr_AverageAnnualReturnSinceInception

3.33%

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

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption Fee (as a percentage of Amount Redeemed)

rr_MaximumDeferredSalesChargeOverOther

none

rr_RedemptionFeeOverRedemption

2.00%

rr_ManagementFeesOverAssets

0.75%

rr_DistributionAndService12b1FeesOverAssets

0.50%

rr_OtherExpensesOverAssets

1.56%

rr_ExpensesOverAssets

2.81%

^[5]

Total Annual Fund Operating Expenses After Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

1.36%

^[5]

rr_NetExpensesOverAssets

1.45%

^[5]

rr_ExpenseExampleYear01

$ 148

rr_ExpenseExampleYear03

742

rr_ExpenseExampleYear05

1,363

rr_ExpenseExampleYear10

3,039

rr_ExpenseExampleNoRedemptionYear01

148

rr_ExpenseExampleNoRedemptionYear03

742

rr_ExpenseExampleNoRedemptionYear05

1,363

rr_ExpenseExampleNoRedemptionYear10

$ 3,039

rr_AverageAnnualReturnYear01

(3.51%)

rr_AverageAnnualReturnYear05

3.47%

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Class C

rr_AverageAnnualReturnSinceInception

3.42%

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

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption Fee (as a percentage of Amount Redeemed)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[8]

rr_RedemptionFeeOverRedemption

2.00%

rr_ManagementFeesOverAssets

0.75%

rr_DistributionAndService12b1FeesOverAssets

1.00%

rr_OtherExpensesOverAssets

1.49%

rr_ExpensesOverAssets

3.24%

^[5]

Total Annual Fund Operating Expenses After Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

1.29%

^[5]

rr_NetExpensesOverAssets

1.95%

^[5]

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

The Class C CDSC is only applicable if you sell your shares within one year after the last day of the month of purchase. See “Shareholder Information—How To Redeem Fund Shares” for a complete discussion of the CDSC.

rr_ExpenseExampleYear01

$ 298

rr_ExpenseExampleYear03

878

rr_ExpenseExampleYear05

1,581

rr_ExpenseExampleYear10

3,178

rr_ExpenseExampleNoRedemptionYear01

198

rr_ExpenseExampleNoRedemptionYear03

878

rr_ExpenseExampleNoRedemptionYear05

1,581

rr_ExpenseExampleNoRedemptionYear10

$ 3,178

rr_AverageAnnualReturnYear01

(5.09%)

rr_AverageAnnualReturnYear05

2.94%

(MSIF - Emerging Markets Fixed Income Opportunities Portfolio) | (Emerging Markets Fixed Income Opportunities Portfolio) | Class R6

rr_AverageAnnualReturnSinceInception

2.78%

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

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption Fee (as a percentage of Amount Redeemed)

rr_MaximumDeferredSalesChargeOverOther

none

rr_RedemptionFeeOverRedemption

2.00%

rr_ManagementFeesOverAssets

0.75%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

12.50%

rr_ExpensesOverAssets

13.25%

^[5]

Total Annual Fund Operating Expenses After Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

12.43%

^[5]

rr_NetExpensesOverAssets

0.82%

^[5]

rr_ExpenseExampleYear01

$ 84

rr_ExpenseExampleYear03

2,621

rr_ExpenseExampleYear05

4,758

rr_ExpenseExampleYear10

8,734

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

2,621

rr_ExpenseExampleNoRedemptionYear05

4,758

rr_ExpenseExampleNoRedemptionYear10

$ 8,734

rr_AverageAnnualReturnYear01

(3.04%)

rr_AverageAnnualReturnYear05

4.11%