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Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName INVESTORS CASH TRUST
Prospectus Date rr_ProspectusDate Aug. 01, 2014
Investment Class Shares | Treasury Portfolio
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Treasury Portfolio
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to provide maximum current income consistent with stability of capital.
Expense [Heading] rr_ExpenseHeading Fees and Expenses of the Fund
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock These are the fees and expenses you may pay when you buy and hold shares.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption SHAREHOLDER FEES

(paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a % of the value of your investment)
Expense Example [Heading] rr_ExpenseExampleHeading EXAMPLE
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This Example 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 for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that 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 Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock The fund is a money market fund that is managed in accordance with federal regulations which govern the quality, maturity, diversity and liquidity of instruments in which a money market fund may invest.

The fund pursues its objective by investing exclusively in short-term US Treasury securities. The timely payment of principal and interest on US Treasury securities is guaranteed by the full faith and credit of the US government.

The fund may invest in floating and variable rate instruments (obligations that do not bear interest at an agreed upon price).

Working in consultation with portfolio management, a credit team screens potential securities and develops a list of those that the fund may buy. Portfolio management, looking for attractive yield and weighing considerations such as credit quality, economic outlooks and possible interest rate movements, then decides which securities on this list to buy.
Risk [Heading] rr_RiskHeading Main Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock There are several risk factors that could reduce the yield you get from the fund, cause the fund's performance to trail that of other investments, or cause you to lose money.

Money market fund risk. An investment in the fund is not insured or guaranteed by the FDIC or any other government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, this share price isn't guaranteed, and if it falls below $1.00 you would lose money. The Advisor is not obligated to take any action to maintain the $1.00 share price. The share price could fall below $1.00 as a result of the actions of one or more large investors in the fund. The credit quality of the fund's holdings can change rapidly in certain markets, and the default of a single holding could cause the fund's share price to fall below $1.00, as could periods of high redemption pressures and/or illiquid markets.

Interest rate risk. Rising interest rates could cause the value of the fund's investments — and therefore its share price as well — to decline. Conversely, any decline in interest rates is likely to cause the fund's yield to decline, and during periods of unusually low interest rates, the fund's yield may approach zero. A low interest rate environment may prevent the fund from providing a positive yield or paying fund expenses out of current income and, at times, could impair the fund's ability to maintain a stable $1.00 share price. Over time, the total return of a money market fund may not keep pace with inflation, which could result in a net loss of purchasing power for long-term investors.

Security selection risk. Although short-term securities are relatively stable investments, it is possible that the securities in which the fund invests will not perform as expected. This could cause the fund's returns to lag behind those of similar money market funds and could result in a decline in share price.

Credit risk. The fund's performance could be hurt and the fund's share price could fall below $1.00 if an issuer suffers an adverse change in financial condition that results in a payment default, security downgrade or inability to meet a financial obligation.

Because of the rising US government debt burden, it is possible that the US government may not be able to meet its financial obligations or that securities issued by the US government may experience credit downgrades. Such a credit event may also adversely impact the financial markets.

Liquidity risk. The liquidity of portfolio securities can deteriorate rapidly due to credit events affecting issuers or due to general market conditions and a lack of willing buyers. When there are no willing buyers and an instrument cannot be readily sold at a desired time or price, the fund may have to accept a lower price or may not be able to sell the instrument at all. An inability to sell one or more portfolio securities can adversely affect the fund's ability to maintain a $1.00 share price or prevent the fund from being able to take advantage of other investment opportunities.

Unusual market conditions, an unusually high volume of redemption requests or other similar conditions could cause the fund to be unable to pay redemption proceeds within a short period of time. If the fund is forced to sell securities at an unfavorable time and/or under unfavorable conditions, such sales may adversely affect the fund's ability to maintain a $1.00 share price.

Regulatory risk. In July 2014, the SEC adopted money market fund reform intended to address potential systemic risks associated with money market funds and to improve transparency for money market fund investors. The fund is required to comply with money market reform over the next 2 years. As a result, the fund may be required to take certain steps that will impact its structure and/or operations, which could impact the return potential of the fund.
Risk Lose Money [Text] rr_RiskLoseMoney There are several risk factors that could reduce the yield you get from the fund, cause the fund's performance to trail that of other investments, or cause you to lose money.
Risk Money Market Fund [Text] rr_RiskMoneyMarketFund Money market fund risk. An investment in the fund is not insured or guaranteed by the FDIC or any other government agency. Although the fund seeks to preserve the value of your investment at $1.00 per share, this share price isn't guaranteed, and if it falls below $1.00 you would lose money. The Advisor is not obligated to take any action to maintain the $1.00 share price. The share price could fall below $1.00 as a result of the actions of one or more large investors in the fund. The credit quality of the fund's holdings can change rapidly in certain markets, and the default of a single holding could cause the fund's share price to fall below $1.00, as could periods of high redemption pressures and/or illiquid markets.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not insured or guaranteed by the FDIC or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Past Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock How a fund's returns vary from year to year can give an idea of its risk. Past performance may not indicate future results. All performance figures below assume that dividends were reinvested. The 7-day yield, which is often referred to as the "current yield," is the income generated by the fund over a seven-day period. This amount is then annualized, which means that we assume the fund generates the same income every week for a year. For more recent performance figures and the current yield, go to deutschefunds.com (the Web site does not form a part of this prospectus) or call the telephone number included in this prospectus.

Performance prior to class inception is based on the performance of the fund's Institutional Shares, adjusted to reflect the higher expenses of Investment Class Shares. Institutional Shares are offered in a separate prospectus.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns How a fund's returns vary from year to year can give an idea of its risk.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress deutschefunds.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance may not indicate future results.
Bar Chart [Heading] rr_BarChartHeading CALENDAR YEAR TOTAL RETURNS (%) (Investment Class Shares)
Bar Chart Narrative [Text Block] rr_BarChartNarrativeTextBlock Returns for other classes were different and are not shown here.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
Best Quarter: 1.17%, Q4 2006 Worst Quarter: 0.00%, Q1 2010
Year-to-Date as of 6/30/14: 0.00%
Performance Table Heading rr_PerformanceTableHeading Average Annual Total Returns
(for periods ended 12/31/2013 expressed as a %)
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock Total returns would have been lower if operating expenses hadn't been reduced.

For more recent performance information, contact the financial services firm from which you obtained this prospectus.
Investment Class Shares | Treasury Portfolio | Investment Class Shares
  
Risk/Return: rr_RiskReturnAbstract  
SHAREHOLDER FEES (paid directly from your investment) rr_ShareholderFeeOther none
Management fee rr_ManagementFeesOverAssets 0.05%
Distribution/Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses rr_OtherExpensesOverAssets 0.28%
Total annual fund operating expenses rr_ExpensesOverAssets 0.58%
1 Year rr_ExpenseExampleYear01 59
3 Years rr_ExpenseExampleYear03 186
5 Years rr_ExpenseExampleYear05 324
10 Years rr_ExpenseExampleYear10 $ 726
2004 rr_AnnualReturn2004 0.67%
2005 rr_AnnualReturn2005 2.52%
2006 rr_AnnualReturn2006 4.35%
2007 rr_AnnualReturn2007 4.33%
2008 rr_AnnualReturn2008 1.32%
2009 rr_AnnualReturn2009 0.03%
2010 rr_AnnualReturn2010 0.01%
2011 rr_AnnualReturn2011 0.01%
2012 rr_AnnualReturn2012 0.01%
2013 rr_AnnualReturn2013 0.01%
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2014
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 0.00%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter:
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Dec. 31, 2006
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.17%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter:
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2010
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn 0.00%
1 Year rr_AverageAnnualReturnYear01 0.01%
5 Years rr_AverageAnnualReturnYear05 0.02%
10 Years rr_AverageAnnualReturnYear10 1.31%
Class Inception rr_AverageAnnualReturnInceptionDate May 18, 2007