Investor Class | T. Rowe Price New Income Fund, Inc. | T. Rowe Price New Income Fund, Inc. | Returns after taxes on distributions and sale of fund shares

Risk/Return:

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1 Year

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4.73%

5 Years

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4.60%

10 Years

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4.23%

Investor Class | T. Rowe Price New Income Fund, Inc.

Risk/Return:

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Risk/Return [Heading]

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T. Rowe Price

New Income Fund

Objective [Heading]

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Investment Objective

Objective, Primary [Text Block]

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The fund seeks the highest level of income consistent with the preservation of capital over time by investing primarily in marketable debt securities.

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)

Portfolio Turnover [Heading]

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Portfolio Turnover

Portfolio Turnover [Text Block]

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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 most recent fiscal year, the fund's portfolio turnover rate was 110.7 % of the average value of its portfolio.

Portfolio Turnover, Rate

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110.70%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

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The figure shown under "Total annual fund operating expenses after fee waiver/expense reimbursement" does not match the "Ratio of expenses to average net assets" shown in the Financial Highlights table, as that figure does not include acquired fund fees and expenses

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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In seeking income and capital preservation, the fund pursues a total return strategy. Active management of the portfolio can result in bonds being sold at gains or losses. However, over the long term, the fund seeks to achieve its objective by investing primarily in income-producing securities that possess what the fund believes are favorable total return (income plus changes in principal) characteristics.

The fund will invest at least 80% of its total assets in income-producing securities, which may include, but are not limited to, U.S. government and agency obligations, mortgage- and asset-backed securities, corporate bonds, foreign securities, collateralized mortgage obligations, Treasury inflation protected securities, and others, including, on occasion, equities.

Eighty percent (80%) of the debt securities purchased by the fund will be rated investment grade (AAA, AA, A, BBB, or an equivalent rating) by each of the major credit rating agencies (Standard & Poor's, Moody's, and Fitch) that have assigned a rating to the security or, if unrated, deemed to be of investment-grade quality by T. Rowe Price. Up to 15% of the fund's total assets may be invested in "split-rated securities," which are securities that have been rated investment grade by at least one rating agency but below investment grade by another rating agency. In addition, the fund may invest up to 5% of its total assets in securities that have received below investment-grade ratings from each of the rating agencies that have assigned ratings to the securities or, if unrated, deemed to be below investment-grade quality by T. Rowe Price.

The fund has considerable flexibility in seeking high yields. There are no maturity restrictions, so the fund can purchase longer-term bonds, which tend to have higher yields than shorter-term issues. However, the portfolio's weighted average maturity is expected to be between four and 15 years. In addition, when there is a large yield difference between the various quality levels, the fund may move down the credit scale and purchase lower-rated bonds with higher yields. When the difference is small or the outlook warrants, the fund may concentrate investments in higher-rated issues.

While most assets will typically be invested in bonds, the fund also invests in derivatives such as interest rate futures and forward currency exchange contracts in keeping with the fund's objective .

The fund may sell holdings for a variety of reasons, such as to adjust the portfolio's average maturity, duration, or credit quality or to shift assets into and out of higher-yielding or lower-yielding securities or different sectors.

Risk [Heading]

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Principal Risks

Risk Narrative [Text Block]

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As with any mutual fund, there is no guarantee that the fund will achieve its objective. The fund's share price fluctuates, which means you could lose money by investing in the fund. The principal risks of investing in this fund are summarized as follows:

Active management risk The fund is subject to the risk that the investment adviser's judgments about the attractiveness, value, or potential appreciation of the fund's investments may prove to be incorrect. If the securities selected and strategies employed by the fund fail to produce the intended results, the fund could underperform other funds with similar objectives and investment strategies.

Interest rate risk This is the risk that a rise in interest rates will cause the price of a fixed rate debt security to fall. Generally, the longer the maturity of a security or weighted average maturity of a fund, the greater the interest rate risk.

Credit risk This is the risk that an issuer of a debt security or counterparty to an over-the-counter derivative could suffer an adverse change in financial condition that results in a payment default, security downgrade, or inability to meet a financial obligation.

Liquidity risk This is the risk that the fund may not be able to sell a holding in a timely manner at a desired price.

Foreign investing risk This is the risk that the fund's investments in foreign securities may be adversely affected by political and economic conditions overseas, reduced liquidity, or decreases in foreign currency values relative to the U.S. dollar.

Prepayment risk and extension risk Prepayment risk is the risk that the principal on mortgage-backed securities, other asset-backed securities or any fixed income security with an embedded call option may be prepaid at any time, which could reduce yield and market value. The rate of prepayments tends to increase as interest rates fall, which could cause the average maturity of the portfolio to shorten. Extension risk may result from a rise in interest rates, which tends to make mortgage-backed securities, asset-backed securities, and other callable fixed income securities more volatile.

Derivatives risk To the extent the fund uses interest rate futures and forward currency exchange contracts , it is exposed to additional volatility in comparison to investing directly in bonds and other debt securities. Derivatives can be illiquid and difficult to value , may involve leverage so that small changes produce disproportionate losses for the fund, and instruments not traded on an exchange are subject to the risk that a counterparty to the transaction will fail to meet its obligations under the derivatives contract. The fund's principal use of derivatives involves the risk that anticipated interest rate movements and changes in currency values and currency exchange rates will not be accurately predicted, which could significantly harm the fund's performance .

Risk Lose Money [Text]

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The fund's share price fluctuates, which means you could lose money by investing in the fund.

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.

Bar Chart [Heading]

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New Income Fund

Calendar Year Returns

Bar Chart Closing [Text Block]

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Quarter

Ended

Total
Return

Best Quarter

6/30/09

5.07%

Worst Quarter

6/30/04

-2.36%

The fund's return for the six months ended 6/30/11 was 2.27%.

Performance Table Heading

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Average Annual Total Returns

Periods ended

December 31, 2010

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as a 401(k) account or individual retirement account.

Performance Table Narrative

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In addition, the average annual total returns table shows hypothetical after-tax returns to suggest how taxes paid by a shareholder may influence returns. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as a 401(k) account or individual retirement account.

Performance Table Closing [Text Block]

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Updated performance information is available through troweprice.com or may be obtained by calling 1 -800-225-5132 .

Investor Class | T. Rowe Price New Income Fund, Inc. | Barclays Capital U.S. Aggregate Bond Index

Risk/Return:

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1 Year

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6.54%

5 Years

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5.80%

10 Years

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5.84%

Investor Class | T. Rowe Price New Income Fund, Inc. | Lipper Corporate Debt Funds A-Rated Average

Risk/Return:

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1 Year

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7.51%

5 Years

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4.78%

10 Years

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5.24%

[1]	Subject to certain exceptions, accounts with a balance of less than $10,000 are charged an annual $20 fee.
[2]	T. Rowe Price Associates, Inc. is required to permanently waive a portion of its management fee charged to the fund in an amount sufficient to fully offset any acquired fund fees and expenses related to investments in other T. Rowe Price mutual funds. The amount of the waiver will vary each fiscal year in proportion to the amount invested in other T. Rowe Price mutual funds. The T. Rowe Price funds would be required to seek regulatory approval in order to terminate this arrangement.
[3]	The figure shown under "Total annual fund operating expenses after fee waiver/expense reimbursement" does not match the "Ratio of expenses to average net assets" shown in the Financial Highlights table, as that figure does not include acquired fund fees and expenses.