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Rowe Price Mid-Cap Growth Fund, Inc.3false0rr_RiskReturnHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <div> <div>T. Rowe Price</div> <div>Mid-Cap Growth Fund</div> <a name="_Toc290550983"> </a>SUMMARY</div></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Summary Investment Objectives/Goals Include the following information, in plain English under rule 421(d) under the Securities Act, in the order and subject matter indicatedReference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 falsefalseRisk/Return [Heading]4false0rr_ObjectiveHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Investment Objective</div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseObjective [Heading]5false0rr_ObjectivePrimaryTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> The fund seeks to provide long-term capital appreciation by investing in mid-cap stocks with potential for above-average earnings growth.</div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a falsefalseObjective, Primary [Text Block]6false0rr_ExpenseHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Fees and Expenses</div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Summary Fee Table Includes the following information, in plain English under rule 421(d) under the Securities Act, after Item 2 Fees and expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Shareholder Fees (fees paid directly from your investment) Example 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 you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be You would pay the following expenses if you did not redeem your shares The Example does not reflect sales charges (loads) on reinvested dividends [and other distributions]. If these sales charges (loads) were included, your costs would be higher. Portfolio Turnover The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs. 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 __% of the average value of its whole portfolio. Instructions. A.3.instructions.6 New Funds. For purposes of this Item, a "New Fund" is a Fund that does not include in Form N-1A financial statements reporting operating results or that includes financial statements for the Fund's initial fiscal year reporting operating results for a period of 6 months or less. The following Instructions apply to New Funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph d -Subsection instructions falsefalseExpense [Heading]7false0rr_ExpenseNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <div> This table describes the fees and expenses that you may pay if you buy and hold shares of the fund. </div> <div> Fees and Expenses of the Fund </div></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThis table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Include the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown.The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount. Modify the narrative explanation to state that Fund shares are sold on a national securities exchange at the end of the time periods indicated, and that brokerage commissions for buying and selling Fund shares through a broker are not reflected.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph b -Subsection instructions falsefalseExpense Narrative [Text Block]8false0rr_ShareholderFeesCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Shareholder fees (fees paid directly from your investment)</div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringShareholder Fees (fees paid directly from your investment).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subsection table falsefalseShareholder Fees Caption [Text]9false0rr_ShareholderFeesTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleShareholderFeesTRowePriceMidCapGrowthFundInc column period compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * row primary compact * ~</div> </div>falsefalse<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleShareholderFeesTRowePriceMidCapGrowthFundInc column period compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * row primary compact * ~</div> </div>falsehttp://www.troweprice.com/role/ScheduleShareholderFeesTRowePriceMidCapGrowthFundIncfalsefalse000102 - Schedule - Shareholder Fees - {T. Rowe Price Mid-Cap Growth Fund, Inc. (Investor Class Shares)}truefalsefalse1falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberColumndei_LegalEntityAxisAxiscik000887147_S000002102MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-05-01T00:00:002011-05-01T00:00:00falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_C000005470Memberrr_ProspectusShareClassAxisexplicitMemberInvestor Class SharesT. Rowe Price Mid-Cap Growth Fund, Inc.T. Rowe Price Mid-Cap Growth Fund, Inc.Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*5false0rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue00falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection table falsefalseMaximum sales charge (load) imposed on purchases0rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricetruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue00falsefalsefalsetruefalseOthernanafalsefalseMaximum sales charge (load) imposed on purchases2falseRowprimaryElement*6false0rr_MaximumDeferredSalesChargeOverOfferingPricerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue00falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph a -Clause i -Subsection instructions falsefalseMaximum deferred sales charge (load)0rr_MaximumDeferredSalesChargeOverOfferingPricetruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue00falsefalsefalsetruefalseOthernanafalsefalseMaximum deferred sales charge (load)3falseRowprimaryElement*7false0rr_RedemptionFeeOverRedemptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truetruetrue00falsefalsefalsetruefalseOtherrr:NonPositivePure4Typepure"Redemption Fee" (as a percentage of amount redeemed, if applicable) If the Fund is an Exchange-Traded Fund and issues or redeems shares in creation units of not less than 25,000 shares each, exclude any fees charged for the purchase and redemption of the Fund's creation units. "Redemption Fee" includes a fee charged for any redemption of the Fund's shares, but does not include a deferred sales charge (load) imposed upon redemption.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 2 -Subparagraph b -Subsection instructions falsefalseRedemption fee0rr_RedemptionFeeOverRedemptiontruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue00falsefalsefalsetruefalseOthernanafalsefalseRedemption fee4falseRowprimaryElement*8false0rr_MaximumAccountFeerrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue1010[1]falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryInclude the caption "Maximum Account Fees" only if the Fund charges these fees. A Fund may omit other captions if the Fund does not charge the fees or expenses covered by the captions. Disclose account fees that may be charged to a typical investor in the Fund; fees that apply to only a limited number of shareholders based on their particular circumstances need not be disclosed. Include a caption describing the maximum account fee (e.g., "Maximum Account Maintenance Fee" or "Maximum Cash Management Fee"). State the maximum annual account fee as either a fixed dollar amount or a percentage of assets. Include in a parenthetical to the caption the basis on which any percentage is calculated. If an account fee is charged only to accounts that do not meet a certain threshold (e.g., accounts under $5)Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph c -Subsection instructions falsefalseMaximum account fee0rr_MaximumAccountFeetruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse[1]1truefalsetrue1010falsefalsefalsetruefalseOthernanafalsefalseMaximum account fee1 Nonretirement accounts with less than a $2,000 balance (with certain exceptions) may be subject to an annual $10 fee.14Shareholder Fees - (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberColumndei_LegalEntityAxisAxiscik000887147_S000002102MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ShareholderFeesData.No authoritative reference available.falsefalseShareholder Fees [Table]10false0rr_OperatingExpensesCaptionrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Annual fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)</div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringAnnual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investment)Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 7 -Subsection table falsefalseOperating Expenses Caption [Text]11false0rr_AnnualFundOperatingExpensesTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleAnnualFundOperatingExpensesTRowePriceMidCapGrowthFundInc column period compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * row primary compact * ~</div> </div>falsefalse<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleAnnualFundOperatingExpensesTRowePriceMidCapGrowthFundInc column period compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * row primary compact * ~</div> </div>falsehttp://www.troweprice.com/role/ScheduleAnnualFundOperatingExpensesTRowePriceMidCapGrowthFundIncfalsefalse000103 - Schedule - Annual Fund Operating Expenses - {T. Rowe Price Mid-Cap Growth Fund, Inc.(Investor Class Shares)}truefalsefalse1falseColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberColumndei_LegalEntityAxisAxiscik000887147_S000002102MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2011-05-01T00:00:002011-05-01T00:00:00falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_C000005470Memberrr_ProspectusShareClassAxisexplicitMemberInvestor Class SharesT. Rowe Price Mid-Cap Growth Fund, Inc.T. Rowe Price Mid-Cap Growth Fund, Inc.Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowprimaryElement*5false0rr_ManagementFeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00650.0065falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureManagement Fees include investment advisory fees (including any fees based on the Fund's performance), any other management fees payable to the investment adviser or its affiliates, and administrative fees payable to the investment adviser or its affiliates that are not included as "Other Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph a -Subsection instructions falsefalseManagement fees0rr_ManagementFeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00650.0065falsefalsefalsetruefalseOthernanafalsefalseManagement fees2falseRowprimaryElement*6false0rr_DistributionAndService12b1FeesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00000.0000falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureDistribution [and/or Service] (12b-1) Fees" include all distribution or other expenses incurred during the most recent fiscal year under a plan adopted pursuant to rule 12b-1 [17 CFR 270.12b-1]. Under an appropriate caption or a subcaption of "Other Expenses," disclose the amount of any distribution or similar expenses deducted from the Fund's assets other than pursuant to a rule 12b-1 plan.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 9 -Subsection table falsefalseDistribution and service (12b-1) fees0rr_DistributionAndService12b1FeesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00000.0000falsefalsefalsetruefalseOthernanafalsefalseDistribution and service (12b-1) fees3falseRowprimaryElement*7false0rr_OtherExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00150.0015falsefalsefalsetruefalseOtherrr:NonNegativePure4Typepure"Other Expenses" include all expenses not otherwise disclosed in the table that are deducted from the Fund's assets or charged to all shareholder accounts. The amount of expenses deducted from the Fund's assets are the amounts shown as expenses in the Fund's statement of operations (including increases resulting from complying with paragraph 2(g) of rule 6-07 of Regulation S-X [17 CFR 210.6-07]). "Other Expenses" do not include extraordinary expenses as determined under generally accepted accounting principles (see Accounting Principles Board Opinion No. 30). If extraordinary expenses were incurred that materially affected the Fund's "Other Expenses," disclose in a footnote to the table what "Other Expenses" would have been had the extraordinary expenses been included.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph c -Clause i -Subsection instructions falsefalseOther expenses0rr_OtherExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00150.0015falsefalsefalsetruefalseOthernanafalsefalseOther expenses4falseRowprimaryElement*8false0rr_ExpensesOverAssetsrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truetruetrue0.00800.0080falsefalsefalsetruefalseOtherrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses. If the Fund is a Feeder Fund, reflect the aggregate expenses of the Feeder Fund and the Master Fund in a single fee table using the captions provided. In a footnote to the fee table, state that the table and Example reflect the expenses of both the Feeder and Master Funds. If the prospectus offers more than one Class of a Multiple Class Fund or more than one Feeder Fund that invests in the same Master Fund, provide a separate response for each Class or Feeder Fund. Base the percentages of "Annual Fund Operating Expenses" on amounts incurred during the Fund's most recent fiscal year, but include in expenses amounts that would have been incurred absent expense reimbursement or fee waiver arrangements. If the Fund has changed its fiscal year and, as a result, the most recent fiscal year is less than three months, use the fiscal year prior to the most recent fiscal year as the basis for determining "Annual Fund Operating Expenses."Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subparagraph d -Subsection instructions truefalseTotal annual fund operating expenses0rr_ExpensesOverAssetstruefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.00800.0080falsefalsefalsetruefalseOthernanafalsefalseTotal annual fund operating expenses14Annual Fund Operating Expenses - UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*Columndei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberColumndei_LegalEntityAxisAxiscik000887147_S000002102MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to OperatingExpensesData.No authoritative reference available.falsefalseAnnual Fund Operating Expenses [Table]12false0rr_ExpenseExampleHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Example </div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringHeading for Expense Example.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalseExpense Example [Heading]13false0rr_ExpenseExampleNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> 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:</div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringThe Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 1 -Subsection example falsefalseExpense Example Narrative [Text Block]14false0rr_ExpenseExampleWithRedemptionTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleExpenseExampleTransposedTRowePriceMidCapGrowthFundInc row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * ~</div> </div>falsefalse<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleExpenseExampleTransposedTRowePriceMidCapGrowthFundInc row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * ~</div> </div>truehttp://www.troweprice.com/role/ScheduleExpenseExampleTransposedTRowePriceMidCapGrowthFundIncfalsefalse000104 - Schedule - Expense Example {Transposed} - {T. Rowe Price Mid-Cap Growth Fund, Inc. (Investor Class Shares)}truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*5false0rr_ExpenseExampleYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue8282falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 4 -Subsection instructions falsefalse1 yearduration2011-05-01T00:00:002011-05-01T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_ExpenseExampleYear03rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue255255falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse3 yearsduration2011-05-01T00:00:002011-05-01T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_ExpenseExampleYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue444444falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse5 yearsduration2011-05-01T00:00:002011-05-01T00:00:00falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*8false0rr_ExpenseExampleYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsetrue990990falsefalsefalsetruefalseMonetaryrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 1 -Subparagraph 2 -Subsection example falsefalse10 yearsduration2011-05-01T00:00:002011-05-01T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_C000005470Memberrr_ProspectusShareClassAxisexplicitMemberInvestor Class SharesT. Rowe Price Mid-Cap Growth Fund, Inc.T. Rowe Price Mid-Cap Growth Fund, Inc.Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue8282falsefalsefalsetruefalse2truefalsetrue255255falsefalsefalsetruefalse3truefalsetrue444444falsefalsefalsetruefalse4truefalsetrue990990falsefalsefalsetruefalseOthernanafalsefalseInvestor Class Shares T. Rowe Price Mid-Cap Growth Fund, Inc.41Expense Example - (USD $)UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to ExpenseExample.No authoritative reference available.falsefalseExpense Example, With Redemption [Table]15false0rr_PortfolioTurnoverHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Portfolio Turnover   </div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 5 -Subsection instructions falsefalsePortfolio Turnover [Heading]16false0rr_PortfolioTurnoverTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> 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 30.1% of the average value of its portfolio.</div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Paragraph 3 -Subsection example falsefalsePortfolio Turnover [Text Block]17false0rr_StrategyHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> <div> Investments, Risks, and Performance</div> <div> Principal Investment Strategies   </div></div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a falsefalseStrategy [Heading]18false0rr_StrategyNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <div> The fund will normally invest at least 80% of its net assets (including any borrowings for investment purposes) in a diversified portfolio of common stocks of mid-cap companies whose earnings T. Rowe Price expects to grow at a faster rate than the average company. The fund defines mid-cap companies as those whose market capitalization (number of shares outstanding multiplied by share price) falls within the range of either the S&P MidCap 400 Index or the Russell Midcap Growth Index. As of December  31, 2010 , the market capitalization ranges for the S&P MidCap 400 Index and the Russell Midcap Growth Index were approximately $ 460 million to $ 9.2 billion, and $ 752 million to $ 21.8 billion, respectively. The market capitalization of the companies in the fund's portfolio and the S&P and Russell indices changes over time; the fund will not automatically sell or cease to purchase stock of a company it holds just because the company's market capitalization grows or falls outside these ranges. As "growth" investors, T.   Rowe Price believes that when a company's earnings grow faster than both inflation and the overall economy, the market will eventually reward it with a higher stock price. In selecting investments, we generally favor companies with one or more of the following: ·     proven products or services; ·     a record of above-average earnings growth; ·     demonstrated potential to sustain earnings growth; ·     connection to an industry experiencing increasing demand; or ·     stock prices that appear to undervalue their growth prospects. In pursuing its investment objective, the fund has the discretion to deviate from its normal investment criteria, as previously described, and purchase securities that the fund's management believes will provide an opportunity for substantial appreciation. These situations might arise when the fund's management believes a security could increase in value for a variety of reasons, including an extraordinary corporate event, a new product introduction or innovation, a favorable competitive development, or a change in management. While most assets will typically be invested in U.S. common stocks, the fund may invest in foreign stocks in keeping with the fund's objectives. The fund may sell securities for a variety of reasons, such as to secure gains, limit losses, or redeploy assets into more promising opportunities.</div></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a falsefalseStrategy Narrative [Text Block]19false0rr_RiskHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Principal Risks </div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNarrative Risk Disclosure.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subsection b falsefalseRisk [Heading]20false0rr_RiskNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> 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. Risks of stock investing   Stocks generally fluctuate in value more than bonds and may decline significantly over short time periods. There is a chance that stock prices overall will decline because stock markets tend to move in cycles, with periods of rising prices and falling prices. The value of a stock in which the fund invests may decline due to general weakness in the stock market or because of factors that affect a company or a particular industry. Market capitalization risk   Investing primarily in issuers within the same market capitalization category carries the risk that the category may be out of favor due to current market conditions or investor sentiment. Because the fund invests primarily in securities issued by mid-cap companies, it is likely to be more volatile than a fund that focuses on securities issued by large companies. Medium-sized companies typically have less seasoned management, narrower product lines, and less capital reserves and liquidity than larger companies, and are therefore more sensitive to economic, market, and industry changes. Investment style risk   Different investment styles tend to shift in and out of favor, depending on market conditions and investor sentiment. The fund's growth approach to investing could cause it to underperform other stock funds that employ a different investment style. Growth stocks tend to be more volatile than value stocks and their prices usually fluctuate more dramatically than the overall stock market. A stock with growth characteristics can have sharp price declines due to decreases in current or expected earnings and may lack dividends that can help cushion its share price in a declining market. 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.</div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringNarrative Risk Disclosure. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 1 -Subparagraph i -Clause instruction -Subsection b falsefalseRisk Narrative [Text Block]21false0rr_BarChartAndPerformanceTableHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData">  Performance   </div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalseBar Chart and Performance Table [Heading]22false0rr_PerformanceNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <div> 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.</div>   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 . </div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalsePerformance Narrative [Text Block]23false0rr_BarChartHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Mid-Cap Growth Fund Calendar Year Returns</div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subsection b falsefalseBar Chart [Heading]24false0rr_BarChartTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleAnnualTotalReturnsTRowePriceMidCapGrowthFundIncInvestorClassSharesBarChart column period compact * column primary compact * row dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember row dei_LegalEntityAxis compact cik000887147_S000002102Member row rr_ProspectusShareClassAxis compact * ~</div> </div>falsefalseBarChart1.jpg<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleAnnualTotalReturnsTRowePriceMidCapGrowthFundIncInvestorClassSharesBarChart column period compact * column primary compact * row dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember row dei_LegalEntityAxis compact cik000887147_S000002102Member row rr_ProspectusShareClassAxis compact * ~</div> </div>falsehttp://www.troweprice.com/role/ScheduleAnnualTotalReturnsTRowePriceMidCapGrowthFundIncInvestorClassSharesBarChartfalsefalse000106 - Schedule - Annual Total Returns - {T. Rowe Price Mid-Cap Growth Fund, Inc. (Investor Class Shares)}truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*5false0rr_AnnualReturn2001rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.0098-0.0098falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2001duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*6false0rr_AnnualReturn2002rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.2122-0.2122falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2002duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*7false0rr_AnnualReturn2003rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.38210.3821falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 2003duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$4falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*8false0rr_AnnualReturn2004rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.18390.1839falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 2004duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$5falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*9false0rr_AnnualReturn2005rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.14820.1482falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2005duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$6falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*10false0rr_AnnualReturn2006rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.06790.0679falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2006duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$7falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*11false0rr_AnnualReturn2007rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.17650.1765falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 2007duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$8falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*12false0rr_AnnualReturn2008rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.3969-0.3969falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2008duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$9falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*13false0rr_AnnualReturn2009rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.45440.4544falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a -Subsection b falsefalseAnnual Return 2009duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$10falseColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*14false0rr_AnnualReturn2010rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.28060.2806falsefalsefalsetruefalseOtherxbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseAnnual Return 2010duration2011-05-01T00:00:002011-05-01T00:00:00Unit12Standardhttp://www.xbrl.org/2003/iso4217USDiso42170falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMemberfalsefalseT. 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Rowe Price Mid-Cap Growth Fund, Inc.101Annual Total Returns - UnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*ColumnunitUnit*Rowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to BarChartData.No authoritative reference available.falsefalseBar Chart [Table]25false0rr_BarChartClosingTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> <div>                                           Quarter Ended        Total Return Best Quarter                        12/31/01              21.27 Worst Quarter                    12/31/08             -25.28</div></div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph ii -Subsection b falsefalseBar Chart Closing [Text Block]26false0rr_PerformanceTableHeadingrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div class="MetaData"> Average Annual Total Returns Periods ended December 31, 2010 </div>falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringThis item represents Average Anuual Total Returns. If a Multiple Class Fund offers a Class in the prospectus that converts into another Class after a stated period, compute average annual total returns in the table by using the returns of the other Class for the period after conversion.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit c -Subsection b falsefalsePerformance Table Heading27false0rr_PerformanceTableTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleAverageAnnualTotalReturnsTransposedTRowePriceMidCapGrowthFundInc row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * ~</div> </div>falsefalse<div> <div style="display:none;" >~ http://www.troweprice.com/role/ScheduleAverageAnnualTotalReturnsTransposedTRowePriceMidCapGrowthFundInc row period compact * row primary compact * column dei_DocumentInformationDocumentAxis compact cik000887147_InvestorClassSharesMember column dei_LegalEntityAxis compact cik000887147_S000002102Member column rr_ProspectusShareClassAxis compact * column rr_PerformanceMeasureAxis compact * ~</div> </div>truehttp://www.troweprice.com/role/ScheduleAverageAnnualTotalReturnsTransposedTRowePriceMidCapGrowthFundIncfalsefalse000107 - Schedule - Average Annual Total Returns {Transposed} - {T. 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(Investor Class Shares)}truefalsefalse1falseColumnperiodPeriod*ColumnprimaryElement*5false0rr_AverageAnnualReturnYear01rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.28060.2806falsefalsefalsetruefalse2truetruetrue0.27340.2734falsefalsefalsetruefalse3truetruetrue0.19190.1919falsefalsefalsetruefalse4truetruetrue0.26640.2664falsefalsefalsetruefalse5truetruetrue0.26380.2638falsefalsefalsetruefalse6truetruetrue0.25660.2566falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalse1 Yearduration2011-05-01T00:00:002011-05-01T00:00:00falseUSDfalsefalse$2falseColumnperiodPeriod*ColumnprimaryElement*6false0rr_AverageAnnualReturnYear05rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.07130.0713falsefalsefalsetruefalse2truetruetrue0.06240.0624falsefalsefalsetruefalse3truetruetrue0.05950.0595falsefalsefalsetruefalse4truetruetrue0.05730.0573falsefalsefalsetruefalse5truetruetrue0.04880.0488falsefalsefalsetruefalse6truetruetrue0.06220.0622falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalse5 Yearsduration2011-05-01T00:00:002011-05-01T00:00:00falseUSDfalsefalse$3falseColumnperiodPeriod*ColumnprimaryElement*7false0rr_AverageAnnualReturnYear10rrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.07540.0754falsefalsefalsetruefalse2truetruetrue0.06970.0697falsefalsefalsetruefalse3truetruetrue0.06520.0652falsefalsefalsetruefalse4truetruetrue0.07160.0716falsefalsefalsetruefalse5truetruetrue0.03120.0312falsefalsefalsetruefalse6truetruetrue0.02590.0259falsefalsefalsetruefalseOtherxbrli:pureItemTypepureReturn Before Taxes.Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 -Subsection b falsefalse10 Yearsduration2011-05-01T00:00:002011-05-01T00:00:00falseUSDfalsefalse$1falseRowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_C000005470Memberrr_ProspectusShareClassAxisexplicitMembertruefalseBefore Taxesrr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberInvestor Class SharesT. Rowe Price Mid-Cap Growth Fund, Inc.T. Rowe Price Mid-Cap Growth Fund, Inc.Before TaxesUnit12Standardhttp://www.xbrl.org/2003/iso4217USDiso421700truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.28060.2806falsefalsefalsetruefalse2truetruetrue0.07130.0713falsefalsefalsetruefalse3truetruetrue0.07540.0754falsefalsefalsetruefalseOthernanafalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.2falseRowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.rr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_C000005470Memberrr_ProspectusShareClassAxisexplicitMemberfalsefalseReturns after taxes on distributionsrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldirr_AfterTaxesOnDistributionsMemberrr_PerformanceMeasureAxisexplicitMemberInvestor Class SharesT. 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Rowe Price Mid-Cap Growth Fund, Inc.Share ClassesS&P MidCap 400 IndexStandard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.26640.2664falsefalsefalsetruefalse2truetruetrue0.05730.0573falsefalsefalsetruefalse3truetruetrue0.07160.0716falsefalsefalsetruefalseOthernanafalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc. S&P MidCap 400 Index5falseRowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMembertruefalseShare Classesrr_ProspectusShareClassAxisrr_ShareClassDomainrr_ProspectusShareClassAxisexplicitMemberfalsefalseRussell Midcap Growth Indexrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_RussellMidcapGrowthIndexMemberrr_PerformanceMeasureAxisexplicitMemberInvestor Class SharesT. Rowe Price Mid-Cap Growth Fund, Inc.Share ClassesRussell Midcap Growth IndexStandard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.26380.2638falsefalsefalsetruefalse2truetruetrue0.04880.0488falsefalsefalsetruefalse3truetruetrue0.03120.0312falsefalsefalsetruefalseOthernanafalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc. Russell Midcap Growth Index6falseRowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalseInvestor Class Sharesdei_DocumentInformationDocumentAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_InvestorClassSharesMemberdei_DocumentInformationDocumentAxisexplicitMemberfalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc.dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_S000002102Memberdei_LegalEntityAxisexplicitMembertruefalseShare Classesrr_ProspectusShareClassAxisrr_ShareClassDomainrr_ProspectusShareClassAxisexplicitMemberfalsefalseLipper Mid-Cap Growth Funds Indexrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldicik000887147_LipperMidCapGrowthFundsIndexMemberrr_PerformanceMeasureAxisexplicitMemberInvestor Class SharesT. Rowe Price Mid-Cap Growth Fund, Inc.Share ClassesLipper Mid-Cap Growth Funds IndexStandard00truefalsefalsefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.25660.2566falsefalsefalsetruefalse2truetruetrue0.06220.0622falsefalsefalsetruefalse3truetruetrue0.02590.0259falsefalsefalsetruefalseOthernanafalsefalseT. Rowe Price Mid-Cap Growth Fund, Inc. Lipper Mid-Cap Growth Funds Index36Average Annual Total Returns - Investor Class SharesUnKnownUnKnownUnKnownUnKnownfalsetrueColumnperiodPeriod*ColumnprimaryElement*Rowdei_DocumentInformationDocumentAxisAxiscik000887147_InvestorClassSharesMemberRowdei_LegalEntityAxisAxiscik000887147_S000002102MemberRowrr_ProspectusShareClassAxisAxis*Rowrr_PerformanceMeasureAxisAxis*RowunitUnit*falsefalsefalseOtherus-types:textBlockItemTypestringContains a command for the SEC Viewer for the role corresponding to PerformanceTableData.No authoritative reference available.falsefalsePerformance [Table]28false0rr_PerformanceTableNarrativeTextBlockrrfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00<div> <div class="MetaData"> Updated performance information is available through troweprice.com or may be obtained by calling 1-800-225-5132. </div> </div>falsefalsefalsefalsefalseOtherus-types:textBlockItemTypestringIf the Fund has annual returns for at least one calendar year, provide a table showing the Fund's (A) average annual total return; (B) average annual total return (after taxes on distributions); and (C) average annual total return (after taxes on distributions and redemption). A Money Market Fund should show only the returns described in clause (A) of the preceding sentence. All returns should be shown for 1-, 5-, and 10- calendar year periods ending on the date of the most recently completed calendar year (or for the life of the Fund, if shorter), but only for periods subsequent to the effective date of the Fund's registration statement. The table also shouldshow the returns of an appropriate broadbased securities market index as defined in Instruction 5 to Item 22(b)(7) for the same periods. A Fund that has been in existence for more than 10 years also may include returns for the life of the Fund. A Money Market Fund may provide the Fund's 7-day yield ending on the date of the most recent calendar year or disclose a toll-free (or collect) telephone number that investors can use to obtain the Fund's current 7-day yield. For a Fund (other than a Money Market Fund or a Fund described in General Instruction C.3.(d)(iii)), provide the information in the following table with the specified captions AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, _____). For a Fund that provides annual total returns for only one calendar year or for a Fund that does not include the bar chart because it does not have annual returns for a full calendar year, modify, as appropriate, the narrative explanation required by paragraph (c)(2)(i) (e.g., by stating that the information gives some indication of the risks of an investment in the Fund by comparing the Fund's performance with a broad measure of market performance).Reference 1: 1 -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Paragraph 2 -Subparagraph iv -Subsection b falsefalsePerformance Table Narrative127Risk/Return Summary - (T. Rowe Price Mid-Cap Growth Fund, Inc.) (Investor Class Shares) (Investor Class Shares, T. 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