The fund seeks to provide preservation of capital, liquidity, and, consistent with these objectives, the highest current income exempt from federal income taxes.

Expense [Heading]

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Fees and Expenses

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold shares of the fund.

Shareholder Fees Caption [Text]

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Fees and Expenses of the Fund

Shareholder fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

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Annual fund operating expenses
(expenses that you pay each year as a
percentage of the value of your investment)

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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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]

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Investments, Risks, and Performance

Principal Investment Strategies

Strategy Narrative [Text Block]

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The fund is a money fund managed in compliance with Rule 2a-7 under the Investment Company Act of 1940. The fund is managed to provide a stable share price of $1.00 by investing in high-quality municipal securities whose income is expected to be exempt from federal income taxes.

The fund's weighted average maturity will not exceed 60 days, its weighted average life will not exceed 120 days, and the fund will not purchase any security with a maturity longer than what is permitted under Rule 2a-7. When calculating its weighted average maturity, a fund may shorten its maturity by using the interest rate resets of certain adjustable rate securities. A fund may not take into account these resets when calculating its weighted average life.

The fund buys securities within the two highest short-term rating categories assigned by established credit rating agencies or, if unrated, deemed to be of comparable quality by T. Rowe Price. All securities purchased by the fund present minimal credit risk in the opinion of T. Rowe Price. In selecting securities for the fund, the portfolio manager may examine relationships among yields of various types and maturities of money market securities in the context of interest rate outlooks. Its yield will fluctuate with changes in short-term interest rates.

Normally, at least 80% of the fund's income will be exempt from federal income taxes. The fund does not purchase bonds that are subject to the alternative minimum tax .

From time to time, the fund may invest a significant portion of its assets in sectors with special risks, such as health care , electric utility, or private activity bonds. The fund may sell holdings for a variety of reasons, such as to adjust the portfolio's average maturity, or to shift assets into or out of higher-yielding securities.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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As with any mutual fund, there can be no guarantee the fund will achieve its objective. Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Recently, money market funds have experienced significant pressures from shareholder redemptions, issuer credit downgrades , illiquid markets , and historically low yields on the securities they can hold. There have been a very small number of money market funds in other fund complexes that have "broken the buck," which means that the fund's investors did not receive $1.00 per share for their investment in those funds. You should be aware that the fund's investment adviser is under no obligation to provide financial support to the fund or take other measures to ensure that you receive $1.00 per share for your investment in the fund.The potential for realizing a loss of principal in the fund could derive from:

Credit risk This is the risk that an issuer of a debt security could suffer an adverse change in financial condition that results in a payment default, security downgrade, or inability to meet a financial obligation. Rule 2a-7 under the Investment Company Act of 1940 requires that money funds invest in securities rated in the highest two credit categories. However, the credit quality of the securities held by the fund may change rapidly in certain market environments.

Interest rate risk This is the risk that a decline in interest rates will lower a fund's yield, or that a rise in the overall level of interest rates will cause a decline in the pricesof fixed income securities held by a fund.The fund's yield will vary; it is not fixed for a specific period like the yield on a bank certificate of deposit. This is a disadvantage when interest rates are falling because the fund would have to reinvest at lower interest rates. During periods of extremely low short-term interest rates, the fund may not be able to maintain a positive yield or yields on par with historical levels. In addition, the recent adoption of more stringent regulations governing the management of money market funds could have a negative effect on the fund's yield and the fund's investment adviser may choose to discontinue its voluntary waiver of the fund's management fee at any time.

Municipal securities risk The fund will be highly impacted by events tied to the overall municipal securities markets, which can be very volatile and significantly affected by unfavorable legislative or political developments and adverse changes in the financial conditions of municipal securities issuers. Income from municipal securities held by the fund could be declared taxable because of changes in tax laws or interpretations by taxing authorities, or noncompliant conduct of a municipal security issuer. In addition, a portion of the fund's otherwise tax-exempt dividends may be taxable to those shareholders subject to the alternative minimum tax.

Certain sectors of the municipal bond market have special risks that can impact such sectors more significantly than the market as a whole. For example, health care can be hurt by rising expenses and dependency on third party reimbursements, electric utilities are subject to governmental rate regulation, and private activity bonds rely on project revenues and the creditworthiness of the corporate user as opposed to governmental support.

Liquidity risk This is the risk that the fund may not be able to sell a security in a timely mannerat a desired price . The fund may experience heavy redemptions, particularly during periods of declining or illiquid markets, which could cause the fund to liquidate its assets at inopportune times or at a depressed value and affect the fund's ability to maintain a $1.00 share price. In addition, the fund may suspend redemptions when permitted by applicable regulations. The secondary market for certain municipal bonds tends to be less developed and liquid than many other securities markets, which may adversely affect the fund's ability to sell such municipal bonds at attractive prices.

Risk Lose Money [Text]

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Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund.

Risk Money Market Fund [Text]

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Although the fund seeks to preserve the value of your investment at $1.00 per share, it is possible to lose money by investing in the fund. 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]

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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]

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Performance

Performance Narrative [Text Block]

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The bar chart showing calendar year returns and the average annual total returns table indicate risk by illustrating how much returns can differ from one year to the next and how fund performance compares with that of a comparable market index. The fund's past performance (before and after taxes) is not necessarily an indication of future performance.

The fund can also experience short-term performance swings, as shown by the best and worst calendar quarter returns during the years depicted.

Performance Information Illustrates Variability of Returns [Text]

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Performance Availability Phone [Text]

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1-800-225-5132

Performance Availability Website Address [Text]

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troweprice.com

Performance Past Does Not Indicate Future [Text]

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The fund's past performance (before and after taxes) is not necessarily an indication of future performance.