Label	Element	Value
Risk Return [Abstract]	rr_RiskReturnAbstract
ProspectusDate	rr_ProspectusDate	Oct. 31, 2012
ACTIVE ASSETS MONEY TRUST (Prospectus Summary) | ACTIVE ASSETS MONEY TRUST
Risk Return [Abstract]	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Active Assets Money Trust
Objective [Heading]	rr_ObjectiveHeading	Investment Objectives
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Active Assets Money Trust is a money market fund that seeks to provide high current income, preservation of capital and liquidity.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund. The Fund is a no-load fund. The Fund does not impose any sales charges.
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	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:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests in high quality, short-term debt obligations. In selecting investments, the Adviser and/or Morgan Stanley Investment Management Limited ("Sub-Adviser") seek to maintain the Fund's share price at $1.00. The Fund's investments include the following money market instruments: corporate obligations (including but not limited to commercial paper); debt obligations of U.S.-regulated banks (including domestic branches or subsidiaries of foreign banks) and instruments secured by those obligations (including certificates of deposit); certificates of deposit of savings banks and savings and loan associations; debt obligations issued or guaranteed as to principal and interest by the U.S. Government, its agencies or instrumentalities, including U.S. government securities guaranteed under the Federal Deposit Insurance Corporation ("FDIC") Temporary Liquidity Guarantee Program; asset-backed securities; U.S. dollar-denominated foreign bank obligations; and repurchase agreements.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	There is no assurance that the Fund will achieve its investment objectives. Although the Fund seeks to preserve the value of your investment at $1.00 per share, if it is unable to do so, it is possible to lose money by investing in the Fund. The principal risks of investing in the Fund include: • Credit and Interest Rate Risk. Debt obligations, such as bonds, are subject   to two types of risk: credit and interest rate risk. Credit risk refers to   the possibility that the issuer 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 debt security resulting from changes in the   general level of interest rates. • U.S. Government Securities. 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. • Asset-Backed Securities. Asset-backed securities involve the risk that the   various federal and state consumer laws and other legal and economic factors   may result in the collateral backing the securities being insufficient to   support payment on the securities. Some asset-backed securities also entail   prepayment risk, which may vary depending on the type of asset. • Foreign Money Market Securities. Investing in money market securities of   foreign issuers involves some additional risks, including the possibility of   adverse political, economic or other developments affecting the issuers of   these securities. • Repurchase Agreements. Repurchase agreements are subject to risks associated   with the possibility of default by the seller at a time when the collateral has   declined in value, or insolvency of the seller, which may affect the Fund's   right to control the collateral and result in certain costs and delays. Shares of the Fund are not bank deposits and are not guaranteed or insured by the FDIC or any other government agency.
Risk Money Market Fund [Text]	rr_RiskMoneyMarketFund	Although the Fund seeks to preserve the value of your investment at $1.00 per share, if it is unable to do so, it is possible to lose money by investing in the Fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	Shares of the Fund are not bank deposits and are not guaranteed or insured by the FDIC or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Past Performance
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing the Fund's average annual returns for the one, five and 10 year periods. The Fund's past performance does not indicate how the Fund will perform in the future.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing the Fund's average annual returns for the one, five and 10 year periods.
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's past performance does not indicate how the Fund will perform in the future.
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns--Calendar Years
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The year-to-date total return as of September 30, 2012 was 0.01%. High Quarter 9/30/07 1.24% Low Quarter 6/30/09 0.00%
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	For the Fund's most recent 7-day annualized yield you may call toll-free (800) 869-NEWS.
Caption	rr_AverageAnnualReturnCaption	Average Annual Total Returns (as of December 31, 2011)
Money Market Seven Day Yield Phone	rr_MoneyMarketSevenDayYieldPhone	(800) 869-NEWS
ACTIVE ASSETS MONEY TRUST (Prospectus Summary) | ACTIVE ASSETS MONEY TRUST | ACTIVE ASSETS MONEY TRUST
Risk Return [Abstract]	rr_RiskReturnAbstract
Advisory Fee	rr_ManagementFeesOverAssets	0.24%
Distribution and Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.10%
Other Expenses	rr_OtherExpensesOverAssets	0.08%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.42%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.19%)	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.23%	[1]
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	These fee waivers and/or expense reimbursements will continue for at least one year or until such time as the Fund's Board of Trustees acts to discontinue all or a portion of such waivers and/or expense reimbursements when it deems such action appropriate.
Expense Example, with Redemption, 1 Year	rr_ExpenseExampleYear01	24
Expense Example, with Redemption, 3 Years	rr_ExpenseExampleYear03	74
Expense Example, with Redemption, 5 Years	rr_ExpenseExampleYear05	130
Expense Example, with Redemption, 10 Years	rr_ExpenseExampleYear10	293
Annual Return 2002	rr_AnnualReturn2002	1.46%
Annual Return 2003	rr_AnnualReturn2003	0.78%
Annual Return 2004	rr_AnnualReturn2004	0.99%
Annual Return 2005	rr_AnnualReturn2005	2.85%
Annual Return 2006	rr_AnnualReturn2006	4.68%
Annual Return 2007	rr_AnnualReturn2007	5.01%
Annual Return 2008	rr_AnnualReturn2008	2.63%
Annual Return 2009	rr_AnnualReturn2009	0.03%
Annual Return 2010	rr_AnnualReturn2010	0.01%
Annual Return 2011	rr_AnnualReturn2011	0.01%
Year to Date Return, Label	rr_YearToDateReturnLabel	The year-to-date total return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2012
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.01%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	High Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2007
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	1.24%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Low Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2009
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	0.00%
1 Year	rr_AverageAnnualReturnYear01	0.01%
5 Years	rr_AverageAnnualReturnYear05	1.52%
10 Years	rr_AverageAnnualReturnYear10	1.83%

[1] The Fund's "Distributor," Morgan Stanley Distribution, Inc., its "Adviser," Morgan Stanley Investment Management Inc., and its "Administrator," Morgan Stanley Services Company Inc., have agreed to waive and/or reimburse all or a portion of the Fund's distribution fee, advisory fee and administration fee, respectively, to the extent that total expenses exceed total income on a daily basis. These fee waivers and/or expense reimbursements will continue for at least one year or until such time as the Fund's Board of Trustees acts to discontinue all or a portion of such waivers and/or expense reimbursements when it deems such action appropriate.