Vanguard Cash Reserves Federal Money Market Fund Investment Risks - Retail Prospectus [Member] - Vanguard Cash Reserves Federal Money Market Fund	Aug. 31, 2025
General Market Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• General Market Risk. The markets in which the Fund invests can be affected by a variety of factors. These factors, which can be real or perceived, may include economic, market, political, and regulatory conditions and developments as well as local, regional, or global events such as wars, military conflicts, natural disasters, and public health issues. In addition, investor sentiment and expectations regarding these factors can also impact the markets. Different parts of the market, including different industries and sectors as well as different types of securities, may react differently to factors that affect the market. These factors can contribute to market uncertainty, market volatility, and fluctuations in the value of the Fund’s investments, thereby resulting in potential losses to the Fund over short or long periods.
Investing in Bond Markets Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• Investing in Bond Markets. The Fund invests in money market instruments, which are high quality, short-term debt securities. As a result, the Fund may be impacted by the general condition of the bond markets and by factors that affect bonds and bond issuers. For example, as a general rule, bond prices and interest rates move in opposite directions. When interest rates rise, bond prices tend to fall, and when interest rates fall, bond prices tend to go up. Bond income also is affected by changes in interest rates. Interest rates can rise or fall for a number of reasons, including, but not limited to, central bank monetary policy, inflationary or deflationary pressures, and changes in general market and economic conditions. Changing interest rates, including, but not limited to, rates that fall below zero, could have unpredictable effects on the overall market and may expose the bond markets in particular to heightened volatility and potential illiquidity. The degree to which the Fund is impacted by certain bond market risks may vary based on factors disclosed in its principal investment strategies, such as the types of bonds in which it invests and the overall credit quality, average maturity, and/or average duration of its bond holdings.
Stable NAV Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• Stable NAV. There can be no assurance that the Fund will be successful in maintaining a stable NAV. A wide variety of factors, such as significant market volatility, very low or negative interest rates, periods of high redemption activity, or other factors could affect the Fund’s ability to maintain a stable NAV.
Money Market Funds and Interest Rates [Member]
Prospectus [Line Items]
Risk [Text Block]	• Money Market Funds and Interest Rates. In general, the prices of money market instruments are less sensitive to changes in interest rates than the prices of longer-term debt securities. However, money market fund income is based on short-term interest rates, which means the Fund’s income may fluctuate significantly over short periods and may decline during periods of falling interest rates. In addition, interest rate changes could have unpredictable impacts on the overall market, which could negatively impact the Fund. For example, the Fund may be subject to loss if interest rates increase substantially and/or rapidly. Depending on the duration and severity, a period of low or negative interest rates could prevent the Fund from, among other things, providing a positive yield to its shareholders, paying expenses out of current income, and/or achieving its investment objective, including maintaining a stable NAV of $1.
Credit Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• Credit Risk. Credit risk refers to the chance that an issuer will default (fail to meet its credit obligations) or fail to make payments in a timely manner, which could result in a loss to the Fund. In addition, negative perceptions of an issuer’s ability to make payments can cause the price of a security to decline. While all debt securities are subject to credit risk to some extent, those with higher credit quality ratings generally pose less credit risk than those with lower credit quality ratings.
Bond Liquidity Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• Bond Liquidity Risk. If the Fund is unable to sell a security at an advantageous time or price, its returns may be reduced. There may be limited trading in the secondary market for certain debt securities, which could make them more difficult to value or sell.
Repurchase Agreements Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• Repurchase Agreements. The Fund invests in repurchase agreements, which are agreements under which the Fund acquires a security from a seller while simultaneously agreeing to resell the security to the seller at an agreed-upon price on a specific date. If the seller does not fulfill its obligation, the Fund could lose money, suffer delays, or incur costs arising from holding or selling the security.
Variable and Floating Rate Securities [Member]
Prospectus [Line Items]
Risk [Text Block]	• Variable and Floating Rate Securities. The Fund may invest in securities that pay variable or floating rates of interest. At any given time, the current interest rate of a variable or floating rate security may not accurately reflect current market interest rates, or may yield less than is appropriate to compensate the investor for the issuer’s current credit quality. As a result, the value of the Fund’s investments in such securities is subject to decline. In addition, an active market for variable and floating rate securities may not always exist at the time the Fund wishes to dispose of them.
Active Management Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• Active Management. The Fund is actively managed. The advisor’s security selection and/or strategy execution could cause the Fund to underperform relevant securities markets or other funds with a similar investment objective.
Industry Concentration Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	• Industry Concentration. The Fund concentrates its investments in securities of issuers in the financial services industry. As a result, the Fund’s performance depends to a greater extent on the overall condition of, and is more susceptible to events affecting, this industry.
Risk Lose Money [Member]
Prospectus [Line Items]
Risk [Text Block]	As with any investment, an investment in the Fund could lose money over any time period.You could lose money by investing in the Fund.
Risk Not Insured [Member]
Prospectus [Line Items]
Risk [Text Block]	An investment in the Fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund May Not Preserve Dollar [Member]
Prospectus [Line Items]
Risk [Text Block]	Although the Fund seeks to preserve the value of your investment at $1 per share, it cannot guarantee it will do so.
Risk Money Market Fund Sponsor May Not Provide Support [Member]
Prospectus [Line Items]
Risk [Text Block]	The Fund’s sponsor is not required to reimburse the Fund for losses, and you should not expect that the sponsor will provide financial support to the Fund at any time, including during periods of market stress.