Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	METROPOLITAN WEST FUNDS
Prospectus Date	rr_ProspectusDate	Jul. 29, 2019
Metropolitan West Investment Grade Credit Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Metropolitan West Investment Grade Credit Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Investment Grade Credit Fund seeks to maximize long-term total return.
Expense [Heading]	rr_ExpenseHeading	Fees and Expenses of the Fund
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. You may pay additional fees to broker-dealers or other financial intermediaries for the purchase of Class I shares of the Fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (Fees paid directly from your investment)
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	July 31, 2020
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	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 annual fund operating expenses or in the example, affect the Fund’s performance. During the period from the Fund’s inception (June 29, 2018) through the most recent fiscal year end, the Fund’s portfolio turnover rate was 199% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	199.00%
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. The cost for the Fund reflects the net expenses of the Fund that result from the contractual expense limitation in the first year only (through July 31, 2020). 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 pursues its objective by utilizing a flexible investment approach that allocates investments across a range of fixed income sectors. Satisfying the Fund’s objective would require it to achieve positive total returns over a full market cycle, i.e., a period of time generally understood to be contained between two consecutive periods of heightened default activity within the global fixed income markets. Total return includes income and capital gains. The Fund invests, under normal circumstances, at least 90% of its net assets in investment grade fixed income securities or unrated securities determined by the Adviser to be of comparable quality. Up to 10% of the Fund’s net assets may be invested in securities rated below investment grade (commonly known as “junk bonds”) or unrated securities determined by the Adviser to be of comparable quality. The emerging market fixed-income securities in which the Fund may invest are not subject to any minimum credit quality standards, so long as the value of those investments does not cause the Fund to exceed its limit on investments in securities rated below investment grade. The Fund invests, under normal circumstances, at least 80% of its net assets, plus any borrowings for investment purposes, in securities and instruments it regards as bonds in the U.S. and abroad, including emerging markets, and may purchase securities of varying maturities issued by domestic and foreign corporations and governments. A bond is a security or instrument having one or more of the following characteristics: a fixed-income security, a security issued at a discount to its face value, a security that pays interest or a security with a stated principal amount that requires repayment of some or all of that principal amount to the holder of the security. The term “bond” is interpreted broadly by the Adviser as an instrument or security evidencing a promise to pay some amount rather than evidencing the corporate ownership of equity, unless that equity represents an indirect or derivative interest in one or more bonds. Bonds for this purpose also include bank loans and instruments that are intended to provide one or more of the characteristics of a direct investment in one or more bonds. The Adviser focuses the Fund’s portfolio holdings in areas of the bond market that the Adviser believes to be relatively undervalued, based on its analysis of quality, sector, coupon or maturity, and that the Adviser believes offer attractive prospective risk-adjusted returns compared to other segments of the bond market. The portfolio management team evaluates each investment idea based on the team’s view of, among other factors, its potential total return, its risk level and how it fits within the Fund’s overall portfolio in determining whether to buy or sell investments. The Adviser allocates the Fund’s assets in response to, among other considerations, changing market, financial, economic, and political factors and events that the Fund’s portfolio managers believe may affect the values of the Fund’s investments. The allocation of capital to sectors and securities within each sector in the Fund is driven primarily by the Adviser’s assessment of relative value offered by each sector and security, respectively. The Adviser seeks to actively manage the Fund’s risks on an on-going basis to mitigate the risks of excessive losses by the portfolio overall. In managing portfolio risk, the Adviser takes into consideration its view of the following factors, among others: the potential relative performance of various market sectors, security selection available within a given sector, the risk/reward equation for different asset classes, liquidity conditions in various market sectors, the shape of the yield curve and projections for changes in the yield curve, potential fluctuations in the overall level of interest rates, and current monetary and fiscal policy. The Fund may invest in securities of any maturity, and there is no limit on the weighted average maturity of the Fund’s portfolio. The Fund does not have a duration target. However, under normal circumstances, the average portfolio duration varies from two to eight years. Duration is a measure of the expected life of a fixed income security that is used to determine the sensitivity of a security to changes in interest rates. The Fund’s investments include various types of bonds and debt securities, including corporate bonds, notes, mortgage-related and asset-backed securities (including collateralized debt obligations, which in turn include collateralized bond obligations and collateralized loan obligations), bank loans, municipal securities, U.S. and non-U.S. money market securities, private placements and restricted securities. The Fund’s fixed income investments may have interest rates that are fixed, variable or floating. The Fund may invest in derivative instruments, primarily currency and other futures, forward contracts, options, and swap agreements (typically interest-rate swaps, index-linked swaps, total return swaps and credit default swaps). Derivatives are used in an effort to hedge investments, for risk management or to increase income or gains for the Fund. The Fund may sell securities and other instruments short provided that not more than 331/3% of its net assets is held as collateral for those transactions. Under normal circumstances, the majority of the Fund’s investments are denominated in U.S. dollars. However, the Fund has the flexibility to allocate up to 20% of its assets to securities denominated in foreign currencies. The Fund reserves the right to hedge its exposure to foreign currencies to reduce the risk of loss from fluctuations in currency exchange rates, but is under no obligation to do so under any circumstances. The Fund may invest up to 10% of its total assets in a combination of convertible bonds, preferred stock, and common stock of domestic and foreign companies.
Risk [Heading]	rr_RiskHeading	Principal Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Because the Fund holds securities with fluctuating market prices, the value of the Fund’s shares will vary as its portfolio securities increase or decrease in value. Therefore, the value of your investment in the Fund could go down as well as up. You can lose money by investing in the Fund. The principal risks affecting the Fund that can cause a decline in value are: Debt Securities Risk: the risk that the value of a debt security may increase or decrease as a result of various factors, including changes in interest rates, actual or perceived inability or unwillingness of issuers to make principal or interest payments, market fluctuations and illiquidity in the debt securities market. Market Risk: the risk that returns from the securities in which the Fund invests may underperform returns from the general securities markets or other types of securities. Interest Rate Risk: the risk that debt securities may decline in value because of changes in interest rates. Credit Risk: the risk that an issuer may default in the payment of principal and/or interest on a security. Issuer Risk: the risk that the value of a security value may decline for reasons directly related to the issuer, such as management performance, financial leverage and reduced demand for the issuer’s goods or services. Price Volatility Risk: the risk that the value of the Fund’s investment portfolio will change as the prices of its investments go up or down. Liquidity Risk: the risk that lack of a ready market or restrictions on resale may limit the ability of the Fund to sell a security at an advantageous time or price. In addition, the Fund, by itself or together with other accounts managed by the Adviser, may hold a position in a security that is large relative to the typical trading volume for that security, which can make it difficult for the Fund to dispose of the position at an advantageous time or price. Over recent years, the fixed-income markets have grown more than the ability of dealers to make markets, which can further constrain liquidity and increase the volatility of portfolio valuations. High levels of redemptions in bond funds in response to market conditions could cause greater losses as a result. Regulations such as the Volcker Rule or future regulations may further constrain the ability of market participants to create liquidity, particularly in times of increased market volatility. The liquidity of the Fund’s assets may change over time. Frequent Trading Risk: the risk that frequent trading may lead to increased portfolio turnover and higher transaction costs, which may reduce the Fund’s performance and may cause higher levels of current tax liability to shareholders of the Fund. Valuation Risk: the risk that the portfolio instruments may be sold at prices different from the values established by the Fund, particularly for investments that trade in low volume, in volatile markets or over the counter or that are fair valued. Prepayment Risk: the risk that in times of declining interest rates, the Fund’s higher yielding securities may be prepaid and the Fund may have to replace them with securities having a lower yield. Extension Risk: the risk that in times of rising interest rates, borrowers may pay off their debt obligations more slowly, causing securities considered short- or intermediate-term to become longer-term securities that fluctuate more widely in response to changes in interest rates than shorter-term securities. Mortgage-Backed Securities Risk: the risk of investing in mortgage-backed securities, including prepayment risk and extension risk. Mortgage-backed securities react differently to changes in interests rates than other bonds, and some mortgage-backed securities are not backed by the full faith and credit of the U.S. government. Asset-Backed Securities Risk: the risk of investing in asset-backed securities, including the risk of loss as a result of the impairment of the value of the underlying financial assets, prepayment risk and extension risk. Issuers of asset-backed securities may have limited ability to enforce the security interest in the underlying assets, and credit enhancements provided to support the asset-backed securities, if any, may be inadequate to protect investors in the event of default. Foreign Investing Risk: the risk that Fund share prices will fluctuate with market conditions, currency exchange rates and the economic and political climates of the foreign countries in which the Fund invests or has exposure. Investments in foreign securities may involve greater risks than investing in U.S. securities due to, among other factors, less publicly available information, less stringent and less uniform accounting, auditing and financial reporting standards, less liquid and more volatile markets, higher transaction and custody costs, additional taxes, less investor protection, delayed or less frequent settlement, political or social instability, civil unrest, acts of terrorism, and regional economic volatility. Foreign Currency Risk: the risk that foreign currencies may decline in value relative to the U.S. dollar and affect the Fund’s investments in foreign currencies, in securities that are denominated, trade and/or receive revenues in foreign currencies, or in derivatives that provide exposure to foreign currencies. Emerging Markets Risk: the risk of investing in emerging market countries, which is substantial due to, among other factors, higher brokerage costs in certain countries; different accounting standards; thinner trading markets as compared to those in developed countries; the possibility of currency transfer restrictions; and the risk of expropriation, nationalization or other adverse political, economic or social developments. U.S. Government Securities Risk: the risk that debt securities issued or guaranteed by certain U.S. government agencies, instrumentalities, and sponsored enterprises are not supported by the full faith and credit of the U.S. government, and as a result, investments in securities or obligations issued by such entities involve credit risk greater than investments in other types of U.S. government securities. Short Sales Risk: the risk that the use of short sales, which are speculative investments, may cause the Fund to lose money if the value of a security does not go down as the Adviser expects. The risk of loss is theoretically unlimited if the value of the security sold short continues to increase. In addition, the use of borrowing and short sales may cause the Fund to have higher expenses (especially interest and dividend expenses) than those of other mutual funds that do not engage in short sales. Derivatives Risk: the risk of investing in derivative instruments, which includes liquidity, interest rate, market, credit and management risks as well as risks related to mispricing or improper valuation. Changes in the value of a derivative may not correlate perfectly with the underlying asset, reference rate or index, and the Fund could lose more than the principal amount invested. These investments can create investment leverage and may create additional risks that may subject the Fund to greater volatility and less liquidity than investments in more traditional securities. Futures Contracts Risk: the risk of investing in futures contracts, which includes (1) the imperfect correlation between a futures contract and the change in market value of the underlying instrument held by the Fund; (2) a high degree of leverage because of the low collateral deposits normally involved in futures trading; (3) possible lack of a liquid secondary market for a futures contract and the resulting inability to close a futures contract when desired; (4) losses caused by unanticipated market movements, which are potentially unlimited; and (5) the inability of the Fund to execute a trade because of the maximum permissible price movements exchanges may impose on futures contracts. Swap Agreements Risk: the risk of investing in swaps, which, in addition to risks applicable to derivatives generally, includes: (1) the inability to assign a swap contract without the consent of the counterparty; (2) potential default of the counterparty to a swap for those not traded through a central counterparty; (3) absence of a liquid secondary market for any particular swap at any time; and (4) possible inability of the Fund to close out a swap transaction at a time that otherwise would be favorable for it to do so. Leverage Risk: the risk that leverage may result from certain transactions, including the use of derivatives and borrowing. This may impair the Fund’s liquidity, cause it to liquidate positions at an unfavorable time, increase its volatility or otherwise cause it not to achieve its intended result. If required by applicable law or regulation, the Fund will reduce leverage risk by either segregating an equal amount of liquid assets or “covering” the transactions that introduce such risk. Equity Risk: the risk that stocks and other equity securities generally fluctuate in value more than bonds and may decline in value over short or extended periods as a result of changes in a company’s financial condition or in overall market, economic and political conditions. Unrated Securities Risk: the risk that unrated securities may be less liquid than comparable rated securities, and the risk that the Adviser may not accurately evaluate the security’s comparative credit rating. Non-U.S. Money Market Securities Risk: the risk of investing in non-U.S. money market securities, which, in addition to risks that are applicable to money market securities generally, such as credit risk and issuer risk, includes currency risk and liquidity risk. Securities Selection Risk: the risk that the securities held by the Fund may underperform those held by other funds investing in the same asset class or those included in benchmarks that are representative of the same asset class because of the portfolio managers’ choice of securities. Portfolio Management Risk: the risk that an investment strategy may fail to produce the intended results. Please see “Principal Risks” and “Other Risks” for a more detailed description of the risks of investing in the Fund. Your investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency, entity, or person.
Risk Lose Money [Text]	rr_RiskLoseMoney	You can lose money by investing in the Fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	Your investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency, entity, or person.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance Information
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	Investment results are not available because the Fund has not been operational for at least one calendar year. Updated performance information for the Fund is available on our website at www.tcw.com or by calling (800) 241-4671.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Investment results are not available because the Fund has not been operational for at least one calendar year.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	(800) 241-4671
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	www.tcw.com
Metropolitan West Investment Grade Credit Fund | M Class
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (Fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.35%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	4.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	4.78%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(4.08%)	[1]
Total Annual Fund Operating Expenses after Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.70%
1 Year	rr_ExpenseExampleYear01	$ 72
3 Years	rr_ExpenseExampleYear03	1,071
5 Years	rr_ExpenseExampleYear05	2,075
10 Years	rr_ExpenseExampleYear10	4,603
Metropolitan West Investment Grade Credit Fund | I Class
Risk/Return:	rr_RiskReturnAbstract
Shareholder Fees (Fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management Fees	rr_ManagementFeesOverAssets	0.35%
Distribution (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	4.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	4.53%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(4.04%)	[1]
Total Annual Fund Operating Expenses after Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.49%
1 Year	rr_ExpenseExampleYear01	$ 50
3 Years	rr_ExpenseExampleYear03	1,001
5 Years	rr_ExpenseExampleYear05	1,962
10 Years	rr_ExpenseExampleYear10	$ 4,402

[1] Metropolitan West Asset Management, LLC (the “Adviser”) has contractually agreed to reduce advisory fees and/or reimburse expenses, including distribution expenses, to limit the Fund’s total annual operating expenses (excluding interest, taxes, brokerage commissions, short sale dividend expenses, acquired fund fees and expenses, and any expenses incurred in connection with any merger or reorganization or extraordinary expenses such as litigation) to the net expenses shown in the table for the applicable share class. The Adviser may recoup reduced fees and expenses only within three years, provided that the recoupment does not cause the Fund’s annual expense ratio to exceed the lesser of (i) the expense limitation applicable at the time of that fee waiver and/or expense reimbursement or (ii) the expense limitation in effect at the time of recoupment. This contract will remain in place until July 31, 2020. Although it does not expect to do so, the Board of Trustees is permitted to terminate that contract sooner in its discretion with written notice to the Adviser.