Objective, Primary [Text Block]

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Objective [Heading]

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Investment Objective

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Morgan Stanley U.S. Government Securities Trust (the "Fund") seeks a high level of current income consistent with safety of principal.

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 and hold shares of the Fund.

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 this 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—How to Exchange Shares—Permissible Fund Exchanges") and including shares of Morgan Stanley Money Market Funds (as defined in the section of the Prospectus entitled "Shareholder Information—How to Exchange Shares—Permissible Fund Exchanges") that you acquired in an exchange of Class A shares of the Fund or Class A 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 financial intermediary and on page 22 of the Prospectus in the section entitled "Shareholder Information— Share Class Arrangements" and in the section of the Fund's Statement of Additional Information ("SAI") entitled "Purchase, Redemption and Pricing of Shares." In addition, Appendix A attached to the Prospectus contains more information regarding financial intermediary-specific sales charge waivers and discounts.

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]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 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 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]

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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 167% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

167.00%

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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The Fund normally invests at least 80% of its net assets in a portfolio of U.S. government securities. This policy may be changed without shareholder approval; however, you would be notified upon 60 days' notice in writing of any changes. In making investment decisions, the Adviser considers economic developments, interest rate trends and other factors. The U.S. government securities that the Fund may purchase include: U.S. Treasury bills, notes and bonds, all of which are direct obligations of the U.S. Government; securities (including mortgage-backed securities) issued by agencies and instrumentalities of the U.S. Government which are backed by the full faith and credit of the United States; securities (including mortgage-backed securities) issued by agencies and instrumentalities which are not backed by the full faith and credit of the United States, but whose issuing agency or instrumentality has the right to borrow, to meet its obligations, from the U.S. Treasury; securities issued by agencies and instrumentalities which are backed solely by the credit of the issuing agency or instrumentality; municipal securities; and securities guaranteed by the U.S. Government or its agencies and instrumentalities or securities supported by the U.S. Government in some other way, such as the discretionary authority of the U.S. Government to purchase certain obligations of the agency or instrumentality. The Fund's investments may include zero coupon securities, which are purchased at a discount and generally accrue interest, but make no payment until maturity.

The mortgage-backed securities in which the Fund may invest include mortgage pass-through securities, commercial mortgage-backed securities ("CMBS"), collateralized mortgage obligations ("CMOs"), stripped mortgage-backed securities ("SMBS") and inverse floating rate obligations ("inverse floaters"). In addition, the Fund may invest in to-be-announced pass-through mortgage securities, which settle on a delayed delivery basis ("TBAs"). The Fund may also invest in asset-backed securities. The Fund may invest in restricted and illiquid securities.

The Fund may, but it is not required to, use derivative instruments for risk management purposes. The Fund's use of derivatives may involve the purchase and sale of derivative instruments such as futures, options, swaps and other related instruments and techniques. These derivative instruments 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.

The Fund is not a money market fund, does not seek to maintain a stable NAV and does not qualify for the tax relief afforded to money market funds by the U.S. Treasury.

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:

U.S. Government Securities. The U.S. government securities in which the Fund invests can be subject to two types of risk: credit risk and interest rate risk. 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. While the credit risk associated with U.S. government securities generally is considered to be minimal, the interest rate risk can be substantial. With respect to U.S. government securities that are not backed by the full faith and credit of the United States, there is the risk that the U.S. Government will not provide financial support to such U.S. government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law.

Zero Coupon Securities. The interest earned on zero coupon securities is, implicitly, automatically compounded and paid out at maturity. While such compounding at a constant rate eliminates the risk of receiving lower yields upon reinvestment of interest if prevailing interest rates decline, the owner of a zero coupon security will be unable to participate in higher yields upon reinvestment of interest received on interest-paying securities if prevailing interest rates rise. A zero coupon security pays no interest to its holder during its life. Therefore, to the extent the Fund invests in zero coupon securities, it will not receive current cash available for distribution to shareholders. In addition, zero coupon securities are subject to substantially greater price fluctuations during periods of changing prevailing interest rates than are comparable securities which pay interest on a current basis.

Credit and Interest Rate Risk. Credit risk refers to the possibility that the issuer or guarantor of a security will be unable to make interest payments and/or repay the principal on its debt. Interest rate risk refers to fluctuations 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 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).

Mortgage-Backed Securities. Mortgage-backed securities entail prepayment risk, which generally increases during a period of falling interest rates. Rising interest rates tend to discourage refinancings, with the result that the average life and volatility of mortgage-backed securities will increase and market price will decrease. Rates of prepayment, faster or slower than expected by the Adviser, could reduce the Fund's yield, increase the volatility of the Fund and/or cause a decline in NAV. Mortgage-backed securities are also subject to extension risk, which is the risk that rising interest rates could cause mortgages or other obligations underlying the securities to be prepaid more slowly than expected, thereby lengthening the duration of such securities, increasing their sensitivity to interest rate changes and causing their prices to decline. Certain mortgage-backed securities may be more volatile and less liquid than other traditional types of debt securities. In addition, mortgage-backed securities are subject to credit risk. An unexpectedly high rate of defaults on the mortgages held by a mortgage pool may adversely affect the value of a mortgage-backed security and could result in losses to the Fund. The risk of such defaults is generally higher in the case of mortgage pools that include subprime mortgages. Furthermore, mortgage-backed securities may be subject to risks associated with the assets underlying those securities, such as a decline in value. Investments in mortgage-backed securities may give rise to a form of leverage (indebtedness) and may cause the Fund's portfolio turnover rate to appear higher. Leverage may cause the Fund to be more volatile than if the Fund had not been leveraged.

Commercial Mortgage-Backed Securities. CMBS are subject to credit risk and prepayment risk. Although prepayment risk is present, it is of a lesser degree in CMBS than in the residential mortgage market; commercial real estate property loans often contain provisions which substantially reduce the likelihood that such securities will be prepaid (e.g., significant prepayment penalties on loans and, in some cases, prohibition on principal payments for several years following origination).

Collateralized Mortgage Obligations. CMOs are comprised of various tranches, the expected cash flows of which have varying degrees of predictability as compared with the underlying mortgage loans or mortgage pass-through entities. The less predictable the cash flow, the higher the yield and the greater the risk. In addition, if the collateral securing CMOs or any third-party guarantees is insufficient to make payments, the Fund could sustain a loss. Like other mortgage backed-securities, some CMOs are subject to credit risk. The Fund invests in both Agency and Non-Agency bonds. Many Agency bonds do not have credit risk as they are government guaranteed.

Stripped Mortgage-Backed Securities. Investments in each class of SMBS are extremely sensitive to changes in interest rates. The interest-only or "IO" class tends to decrease in value substantially if interest rates decline and prepayment rates become more rapid. The principal-only or "PO" class tends to decrease in value substantially if interest rates increase and the rate of prepayment decreases. If the Fund invests in SMBS and interest rates move in a manner not anticipated by Fund management, it is possible that the Fund could lose all or substantially all of its investment. Additionally, some SMBS entail credit risk. The Fund invests in both Agency and Non-Agency bonds. Many Agency bonds do not have credit risk as they are government guaranteed.

Inverse Floaters. Inverse floating rate obligations are obligations that pay interest at rates that vary inversely with changes in market rates of interest. Because the interest rate paid to holders of such obligations is generally determined by subtracting a variable or floating rate from a predetermined amount, the interest rate paid to holders of such obligations will decrease as such variable or floating rate increases and increase as such variable or floating rate decreases.

Municipal Obligations. To the extent the Fund invests in municipal obligations issued by state and local governments and their agencies, the Fund may be susceptible to political, economic, regulatory or other factors affecting issuers of these municipal obligations. To the extent that the Fund invests in municipal obligations of issuers in the same economic sector, it could be more sensitive to economic, business or political developments that affect such sector.

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 changing interest rate environment or in other circumstances 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 and risks that the transactions may not be liquid. Certain derivative transactions may give rise to a form of leverage. Leverage magnifies the potential for gain and the risk of loss.

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 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).

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 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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Past Performance

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 A shares' performance from year-to-year and by showing how the Fund's average annual returns for the past one, five and 10 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 performance information in the bar chart does not reflect the deduction of sales charges; if these amounts were reflected, returns would be less than shown. 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.

Bar Chart [Heading]

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Annual Total Returns—Calendar Years

Bar Chart Does Not Reflect Sales Loads [Text]

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The performance information in the bar chart does not reflect the deduction of sales charges; if these amounts were reflected, returns would be less than shown.

Bar Chart Closing [Text Block]

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High Quarter	06/30/10	3.73
Low Quarter	12/31/16	-2.79

Performance Table Heading

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Average Annual Total Returns For Periods Ended December 31, 2019

^[1]

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 the Class A shares' returns. Actual after-tax returns depend on an 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 ("IRAs"). 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.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

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).

Index No Deduction for Fees, Expenses, Taxes [Text]

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(reflects no deduction for fees, expenses or taxes)

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on an 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 ("IRAs").

Performance Table Explanation after Tax Higher

rr_PerformanceTableExplanationAfterTaxHigher

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.

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.

Performance Information Illustrates Variability of Returns [Text]

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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 the Class A shares' returns.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.morganstanley.com/im

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

1-800-548-7786

(Morgan Stanley U.S. Government Securities Trust) | Bloomberg Barclays U.S. Government/Mortgage Index (reflects no deduction for fees, expenses or taxes)

rr_ProspectusTable

rr_AverageAnnualReturnYear01

6.63%

^[2]

rr_AverageAnnualReturnYear05

2.45%

^[2]

rr_AverageAnnualReturnYear10

3.07%

^[2]

(Morgan Stanley U.S. Government Securities Trust) | Lipper General U.S. Government Funds Index (reflects no deduction for taxes)

rr_AverageAnnualReturnSinceInception

4.81%

^[2],[3]

rr_ProspectusTable

rr_AverageAnnualReturnYear01

6.56%

^[4]

rr_AverageAnnualReturnYear05

2.21%

^[4]

rr_AverageAnnualReturnYear10

3.15%

^[4]

(Morgan Stanley U.S. Government Securities Trust) | Class A

rr_AverageAnnualReturnSinceInception

4.20%

^[3],[4]

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

3.25%

Maximum deferred sales charge (load) (as a percentage based on the lesser of the offering price or NAV at redemption)

rr_MaximumDeferredSalesChargeOverOther

none

^[5]

Distribution and/or Shareholder Service (12b-1) Fee

rr_ManagementFeesOverAssets

0.42%

rr_DistributionAndService12b1FeesOverAssets

0.25%

rr_OtherExpensesOverAssets

0.32%

rr_ExpensesOverAssets

0.99%

^[6]

Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.14%

^[6]

rr_NetExpensesOverAssets

0.85%

^[6]

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 0.50% that will be imposed if you sell your shares within 18 months after the last day of the month of purchase, except for certain specific circumstances. See "Shareholder Information—Share Class Arrangements" for further information about the CDSC waiver categories.

rr_ExpenseExampleYear01

$ 409

rr_ExpenseExampleYear03

617

rr_ExpenseExampleYear05

841

rr_ExpenseExampleYear10

1,486

rr_ExpenseExampleNoRedemptionYear01

409

rr_ExpenseExampleNoRedemptionYear03

617

rr_ExpenseExampleNoRedemptionYear05

841

Highest Quarterly Return, Label

rr_ExpenseExampleNoRedemptionYear10

$ 1,486

Annual Return 2010

rr_AnnualReturn2010

5.03%

Annual Return 2011

rr_AnnualReturn2011

7.54%

Annual Return 2012

rr_AnnualReturn2012

3.86%

Annual Return 2013

rr_AnnualReturn2013

(2.10%)

Annual Return 2014

rr_AnnualReturn2014

5.60%

Annual Return 2015

rr_AnnualReturn2015

0.10%

Annual Return 2016

rr_AnnualReturn2016

2.40%

Annual Return 2017

rr_AnnualReturn2017

2.66%

Annual Return 2018

rr_AnnualReturn2018

(0.01%)

Annual Return 2019

rr_AnnualReturn2019

6.43%

rr_HighestQuarterlyReturnLabel

High Quarter

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

3.73%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Low Quarter

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(2.79%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2016

rr_AverageAnnualReturnYear01

3.00%

^[7]

rr_AverageAnnualReturnYear05

1.62%

^[7]

rr_AverageAnnualReturnYear10

2.77%

^[7]

(Morgan Stanley U.S. Government Securities Trust) | Class A | Return After Taxes on Distributions

rr_AverageAnnualReturnSinceInception

3.67%

^[7]

rr_ProspectusTable

rr_AverageAnnualReturnYear01

1.72%

^[7],[8]

rr_AverageAnnualReturnYear05

0.44%

^[7],[8]

rr_AverageAnnualReturnYear10

1.65%

^[7],[8]

(Morgan Stanley U.S. Government Securities Trust) | Class A | Return After Taxes on Distributions and Sale of Fund Shares

rr_AverageAnnualReturnSinceInception

2.13%

^[7],[8]

rr_ProspectusTable

rr_AverageAnnualReturnYear01

1.76%

^[7]

rr_AverageAnnualReturnYear05

0.70%

^[7]

rr_AverageAnnualReturnYear10

1.65%

^[7]

(Morgan Stanley U.S. Government Securities Trust) | Class L

rr_AverageAnnualReturnSinceInception

2.18%

^[7]

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage based on the lesser of the offering price or NAV at redemption)

rr_MaximumDeferredSalesChargeOverOther

none

Distribution and/or Shareholder Service (12b-1) Fee

rr_ManagementFeesOverAssets

0.42%

rr_DistributionAndService12b1FeesOverAssets

0.50%

rr_OtherExpensesOverAssets

0.33%

rr_ExpensesOverAssets

1.25%

^[6]

Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.13%

^[6]

rr_NetExpensesOverAssets

1.12%

^[6]

rr_ExpenseExampleYear01

$ 114

rr_ExpenseExampleYear03

384

rr_ExpenseExampleYear05

674

rr_ExpenseExampleYear10

1,500

rr_ExpenseExampleNoRedemptionYear01

114

rr_ExpenseExampleNoRedemptionYear03

384

rr_ExpenseExampleNoRedemptionYear05

674

rr_ExpenseExampleNoRedemptionYear10

$ 1,500

rr_AverageAnnualReturnYear01

6.09%

^[7]

rr_AverageAnnualReturnYear05

2.01%

^[7]

rr_AverageAnnualReturnYear10

2.74%

^[7]

(Morgan Stanley U.S. Government Securities Trust) | Class I

rr_AverageAnnualReturnSinceInception

3.39%

^[7]

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage based on the lesser of the offering price or NAV at redemption)

rr_MaximumDeferredSalesChargeOverOther

none

Distribution and/or Shareholder Service (12b-1) Fee

rr_ManagementFeesOverAssets

0.42%

rr_DistributionAndService12b1FeesOverAssets

none

rr_OtherExpensesOverAssets

0.32%

rr_ExpensesOverAssets

0.74%

^[6]

Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.22%

^[6]

rr_NetExpensesOverAssets

0.52%

^[6]

rr_ExpenseExampleYear01

$ 53

rr_ExpenseExampleYear03

214

rr_ExpenseExampleYear05

390

rr_ExpenseExampleYear10

898

rr_ExpenseExampleNoRedemptionYear01

rr_ExpenseExampleNoRedemptionYear03

214

rr_ExpenseExampleNoRedemptionYear05

390

rr_ExpenseExampleNoRedemptionYear10

$ 898

rr_AverageAnnualReturnYear01

6.90%

^[7]

rr_AverageAnnualReturnYear05

2.67%

^[7]

rr_AverageAnnualReturnYear10

3.42%

^[7]

(Morgan Stanley U.S. Government Securities Trust) | Class C

rr_AverageAnnualReturnSinceInception

4.09%

^[7]

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_ProspectusTable

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage based on the lesser of the offering price or NAV at redemption)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[9]

Distribution and/or Shareholder Service (12b-1) Fee

rr_ManagementFeesOverAssets

0.42%

rr_DistributionAndService12b1FeesOverAssets

1.00%

rr_OtherExpensesOverAssets

0.43%

rr_ExpensesOverAssets

1.85%

^[6]

Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.23%

^[6]

rr_NetExpensesOverAssets

1.62%

^[6]

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

The Class C CDSC is only applicable if you sell your shares within one year after purchase. See "Shareholder Information—Share Class Arrangements" for a complete discussion of the CDSC.

rr_ExpenseExampleYear01

$ 265

rr_ExpenseExampleYear03

559

rr_ExpenseExampleYear05

979

rr_ExpenseExampleYear10

2,150

rr_ExpenseExampleNoRedemptionYear01

165

rr_ExpenseExampleNoRedemptionYear03

559

rr_ExpenseExampleNoRedemptionYear05

979

rr_ExpenseExampleNoRedemptionYear10

$ 2,150

rr_AverageAnnualReturnYear01

4.56%

^[7]

rr_AverageAnnualReturnYear05

^[7]

rr_AverageAnnualReturnYear10

^[7]