Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	BLACKROCK LIQUIDITY FUNDS
Prospectus Date	rr_ProspectusDate	Oct. 03, 2016
Cash Reserve | BLACKROCK LIQUIDITY CALIFORNIA MONEY FUND
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Overview Key Facts About California Money Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The investment objective of California Money Fund (the “Fund”), a series of BlackRock Liquidity Funds (the “Trust”), is to seek as high a level of current income that is exempt from federal income tax and, to the extent possible, from California State personal income tax, as is consistent with liquidity and stability of principal.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Cash Reserve Shares of California Money Fund.
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)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	February 28, 2018
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 Strategies of the Fund
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	California Money Fund invests primarily in a broad range of short-term obligations and derivative securities such as beneficial interests in municipal trust certificates and partnership trusts ("Municipal Obligations") issued by or on behalf of the State of California and its authorities, agencies, instrumentalities and political subdivisions. The Fund may also invest in Municipal Obligations issued by or on behalf of other states, territories and possessions of the United States, the District of Columbia and their respective authorities, agencies, instrumentalities and political subdivisions. Under normal circumstances, the Fund will invest at least 80% of its net assets, plus the amount of any borrowing for investment purposes, in Municipal Obligations, the interest on which, in the opinion of counsel to the issuer of the obligation, is exempt from taxation under the Constitution or statutes of California, including municipal securities issued by the State of California and its political subdivisions, as well as certain other governmental issuers, such as the Commonwealth of Puerto Rico, the U.S. Virgin Islands and Guam, that pay interest that, in the opinion of counsel to the issuer, is exempt from federal income tax and from California personal income tax ("California Municipal Obligations"). Dividends paid by the Fund that are derived from interest on California Municipal Obligations are exempt from regular federal and California State personal income tax. Municipal Obligations in which the Fund may invest, however, may be subject to the federal alternative minimum tax, although the Fund does not currently intend to invest in Municipal Obligations that are subject to the federal alternative minimum tax. The Fund invests in securities maturing in 397 days or less (with certain exceptions) and the portfolio will have a dollar-weighted average maturity of 60 days or less and a dollar-weighted average life of 120 days or less. In addition, the Fund may invest in variable and floating rate instruments and when-issued and delayed delivery securities. The securities purchased by the Fund are subject to the quality, diversification, and other requirements of Rule 2a-7 under the Investment Company Act of 1940, as amended (the "1940 Act"), and other rules of the Securities and Exchange Commission. The Fund will only purchase securities that present minimal credit risk as determined by BlackRock, the Fund's investment manager, pursuant to guidelines approved by the Trust's Board of Trustees (the "Board").
Risk [Heading]	rr_RiskHeading	Principal Risks of Investing in the Fund
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Risk is inherent in all investing. You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. The Fund may impose a fee upon the sale of your shares or may temporarily suspend your ability to sell shares if the Fund's liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The Fund's sponsor has no legal obligation to provide financial support to the Fund, and you should not expect that the sponsor will provide financial support to the Fund at any time. The following is a summary description of principal risks of investing in the Fund. Credit Risk — Credit risk refers to the possibility that the issuer of a security will not be able to make payments of principal and interest when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer. Foreign Exposure Risk — Securities issued or supported by foreign entities, including foreign banks and corporations, may involve additional risks and considerations. Extensive public information about the foreign issuer may not be available, and unfavorable political, economic or governmental developments in the foreign country involved could affect the payment of principal and interest. Income Risk — Income risk is the risk that the Fund’s yield will vary as short-term securities in its portfolio mature and the proceeds are reinvested in securities with different interest rates. Interest Rate Risk — Interest rate risk is the risk that the value of a debt security may fall when interest rates rise. In general, the market price of debt securities with longer maturities will go up or down more in response to changes in interest rates than the market price of shorter term securities. Due to fluctuations in interest rates, the market value of such securities may vary during the period shareholders own shares of the Fund. Liquidity Fee and Redemption Gate Risk — The Board has discretion to impose a liquidity fee of up to 2% upon sale of your shares or may temporarily suspend your ability to sell shares if the Fund's liquidity falls below required minimums because of market conditions or other factors. Accordingly, you may not be able to sell your shares or your redemptions may be subject to a liquidity fee when you sell your shares at certain times. Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money. Municipal Securities Concentration Risk — From time to time the Fund may invest a substantial amount of its assets in municipal securities whose interest is paid solely from revenues of similar projects, if such investment is deemed necessary or appropriate by BlackRock. If the Fund concentrates its investments in this manner, it assumes the legal and economic risks relating to such projects and this may have a significant impact on the Fund's investment performance. Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. Certain municipal securities, including private activity bonds, are not backed by the full faith, credit and taxing power of the issuer. Additionally, if events occur after the security is acquired that impact the security's tax-exempt status, the Fund and its shareholders could be subject to substantial tax liabilities. Non-Diversification Risk — The Fund concentrates its investments in securities of issuers located in California. This raises special concerns because the Fund may be more exposed to the risks associated with, and developments affecting, an individual issuer than a fund that invests more widely. In particular, changes in the economic conditions and governmental policies of California and its political subdivisions, including as a result of legislation or litigation changing the taxation of municipal securities or the rights of municipal security holders in the event of bankruptcy, could impact the value of the Fund's shares. Stable Net Asset Value Risk — The Fund may not be able to maintain a stable net asset value ("NAV") of $1.00 per share at all times. If the Fund fails to maintain a stable NAV (or if there is a perceived threat of such a failure), the Fund, along with other money market funds, could be subject to increased redemption activity. State Specific Risk — A substantial part of the portfolio of the Fund will, under normal circumstances, be composed of California Municipal Obligations. As a result, the Fund will be more susceptible to any economic, business and political risks or other developments which generally affect California and the issuers of California Municipal Obligations. With the approval by voters in November 2012 of a seven-year personal income tax increase and a four-year sales tax increase, the State of California has significantly improved its general fiscal condition. However, many local jurisdictions within the State of California face continued fiscal stress. For more information on the risks associated with California Municipal Obligations, see "Non-Diversification Risk" above and "Details about the Funds—Investment Risks—Principal Risks of Investing in the Funds—State Specific Risk—California Money Fund" below as well as Appendix B to the Statement of Additional Information. Taxability Risk — Future laws, regulations, rulings or court decisions may cause interest on municipal securities to be subject, directly or indirectly, to federal income taxation or interest on state municipal securities to be subject to state or local income taxation, or the value of state municipal securities to be subject to state or local intangible personal property tax, or may otherwise prevent the Fund from realizing the full current benefit of the tax-exempt status of such securities. Any such change could also affect the market price of such securities, and thus the value of an investment in the Fund. U.S. Government Obligations Risk — Certain securities in which the Fund may invest, including securities issued by certain U.S. Government agencies and U.S. Government sponsored enterprises, are not guaranteed by the U.S. Government or supported by the full faith and credit of the United States. Variable and Floating Rate Instrument Risk — The absence of an active market for these securities could make it difficult for the Fund to dispose of them if the issuer defaults. When-Issued and Delayed Settlement Transactions Risk — When-issued and delayed delivery securities involve the risk that the security the Fund buys will lose value prior to its delivery. There also is the risk that the security will not be issued or that the other party to the transaction will not meet its obligation. If this occurs, the Fund loses both the investment opportunity for the assets it set aside to pay for the security and any gain in the security's price.
Risk Lose Money [Text]	rr_RiskLoseMoney	You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non-Diversification Risk — The Fund concentrates its investments in securities of issuers located in California. This raises special concerns because the Fund may be more exposed to the risks associated with, and developments affecting, an individual issuer than a fund that invests more widely. In particular, changes in the economic conditions and governmental policies of California and its political subdivisions, including as a result of legislation or litigation changing the taxation of municipal securities or the rights of municipal security holders in the event of bankruptcy, could impact the value of the Fund's shares.
Risk Money Market Fund [Text]	rr_RiskMoneyMarketFund	Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. The Fund may impose a fee upon the sale of your shares or may temporarily suspend your ability to sell shares if the Fund's liquidity falls below required minimums because of market conditions or other factors. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	Because the Cash Reserve Shares of California Money Fund have not yet commenced operations, the performance shown for each of the past ten calendar years is that of the Fund’s Dollar Shares, which are offered by a separate prospectus. Dollar Shares and Cash Reserve Shares of the Fund should have returns and seven-day yields that are substantially the same because they represent interests in the same portfolio securities and their performance should differ only to the extent that they bear different expenses. The information shows you how California Money Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. As with all such investments, past performance is not an indication of future results. The table includes all applicable fees. If BlackRock and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. The Fund is a money market fund managed pursuant to the requirements of Rule 2a-7 under the 1940 Act. Effective May 28, 2010, Rule 2a-7 was amended to impose new liquidity, credit quality and maturity requirements on all money market funds. Fund performance shown prior to May 28, 2010 is based on 1940 Act rules then in effect and is not an indication of future returns. Updated information on the Fund’s performance can be obtained by visiting www.blackrock.com/cash or can be obtained by phone at (800) 441-7450.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The information shows you how California Money Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	(800) 441-7450
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.blackrock.com/cash
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	As with all such investments, past performance is not an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	California Money Fund Dollar Shares ANNUAL TOTAL RETURNS As of 12/31
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	During the ten-year period shown in the bar chart, the highest return for a quarter was 0.82% (quarter ended September 30, 2007) and the lowest return for a quarter was 0.00% (quarter ended December 31, 2015). The year-to-date return as of September 30, 2016 was 0.03%.
Bar Chart, Returns for Class Not Offered in Prospectus [Text]	rr_BarChartReturnsForClassNotOfferedInProspectus	Because the Cash Reserve Shares of California Money Fund have not yet commenced operations, the performance shown for each of the past ten calendar years is that of the Fund’s Dollar Shares, which are offered by a separate prospectus.
Performance Table Heading	rr_PerformanceTableHeading	As of 12/31/15 Average Annual Total Returns
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	Current Yield: You may obtain the Fund’s current 7-day yield by calling (800) 441-7450 or by visiting the Fund’s website at www.blackrock.com/cash.
Money Market Seven Day Yield Phone	rr_MoneyMarketSevenDayYieldPhone	(800) 441-7450
Cash Reserve | BLACKROCK LIQUIDITY CALIFORNIA MONEY FUND | Cash Reserve Shares
Risk/Return:	rr_RiskReturnAbstract
Management Fee	rr_ManagementFeesOverAssets	0.38%	[1]
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Shareholder Servicing Fees	rr_Component1OtherExpensesOverAssets	0.40%	[1]
Miscellaneous/Other Expenses	rr_Component2OtherExpensesOverAssets	0.09%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.49%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.87%	[1]
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.27%)	[1],[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.60%	[1],[2]
1 Year	rr_ExpenseExampleYear01	$ 61
3 Years	rr_ExpenseExampleYear03	251
5 Years	rr_ExpenseExampleYear05	456
10 Years	rr_ExpenseExampleYear10	$ 1,048
Cash Reserve | BLACKROCK LIQUIDITY CALIFORNIA MONEY FUND | Dollar Shares
Risk/Return:	rr_RiskReturnAbstract
2006	rr_AnnualReturn2006	2.97%
2007	rr_AnnualReturn2007	3.18%
2008	rr_AnnualReturn2008	1.54%
2009	rr_AnnualReturn2009	0.09%
2010	rr_AnnualReturn2010	none
2011	rr_AnnualReturn2011	0.14%
2012	rr_AnnualReturn2012	0.01%
2013	rr_AnnualReturn2013	0.02%
2014	rr_AnnualReturn2014	0.01%
2015	rr_AnnualReturn2015	0.01%
Year to Date Return, Label	rr_YearToDateReturnLabel	year-to-date return
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2016
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.03%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2007
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	0.82%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	none
1 Year	rr_AverageAnnualReturnYear01	0.01%
5 Years	rr_AverageAnnualReturnYear05	0.04%
10 Years	rr_AverageAnnualReturnYear10	0.79%
7-Day Yield As of December 31, 2015	rr_MoneyMarketSevenDayYield	0.01%

[1] Fund currently active, but no assets in share class as of the fiscal year ended October 31, 2015.

[2] As described in the "Management of the Funds" section of the Fund's prospectus beginning on page 33, BlackRock Advisors, LLC ("BlackRock"), the Fund's investment manager, has contractually agreed to waive fees and/or reimburse ordinary operating expenses in order to keep combined Management Fees and Miscellaneous/Other Expenses (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) from exceeding 0.20% of average daily net assets through February 28, 2018. The agreement may be terminated upon 90 days' notice by a majority of the non-interested trustees of the Trust or by a vote of a majority of the outstanding voting securities of the Fund.