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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Dec. 31, 2011
Registrant Name dei_EntityRegistrantName T. Rowe Price Index Trust, Inc.
Central Index Key dei_EntityCentralIndexKey 0000858581
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Apr. 26, 2012
Document Effective Date dei_DocumentEffectiveDate May 01, 2012
Prospectus Date rr_ProspectusDate May 01, 2012
T. Rowe Price Equity Index 500 Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

Price Equity Index 500 Fund

SUMMARY
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to match the performance of the Standard & Poor’s 500 Stock Index®.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold shares of the fund.
Shareholder Fees: rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

Fees and Expenses of the Fund

Shareholder fees (fees paid directly from your investment)
Operating Expenses: rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

Annual fund operating expenses

(expenses that you pay each year as a

percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 5.5% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 5.50%
Expense Example: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

Investments, Risks, and Performance

Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The fund seeks to match the performance of the S&P 500 Index by using a full replication strategy. This involves investing substantially all of its assets in all of the stocks in the S&P 500 Index. We attempt to maintain holdings of each stock in proportion to its weight in the index.

The S&P 500 is made up of primarily large-capitalization companies that represent a broad spectrum of the U.S. economy and a substantial part of the U.S. stock market’s total capitalization. (Market capitalization is the number of a company’s outstanding shares multiplied by the market price per share.)

Standard & Poor’s constructs the index by first identifying major industry categories and then allocating a representative sample of the larger and more liquid stocks in those industries to the index. S&P weights each stock according to its total market value. For example, the 50 largest companies in the index may account for over 50% of its value.

Under normal conditions, the fund will invest at least 80% of its net assets (including any borrowings for investment purposes) in stocks that are held in its benchmark index. T. Rowe Price compares the composition of the fund to that of the index. If a material misweighting develops, the portfolio managers seek to rebalance the portfolio in an effort to realign it with its index.

While most assets will be invested in common stocks, the fund may also purchase stock index futures contracts. Futures would typically be used to reduce cash balances in the fund and increase the level of fund assets exposed to common stocks represented in the fund’s benchmark index.

While there is no guarantee, the correlation between the fund and its index is expected to be at least 0.95. A correlation of 1.00 indicates that the returns of the fund and the index will always move in the same direction (but not necessarily by the same amount). A correlation of 0.00 would mean movements in the fund are unrelated to movements in the index.

The fund may sell securities to better align its portfolio with the characteristics of its benchmark or to satisfy redemption requests. However, the fund is not required to sell specific securities that have been removed from its index.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

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:

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. Securities issued by large-cap companies tend to be less volatile than securities issued by smaller companies. However, larger companies may not be able to attain the high growth rates of successful smaller companies, especially during strong economic periods, and may be unable to respond as quickly to competitive challenges.

Index investing risk Because the fund is passively managed and seeks to match the performance of its benchmark index, holdings are generally not reallocated based on changes in market conditions or outlook for a specific security, industry, or market sector. As a result, the fund’s performance may lag the performance of actively managed funds.

Tracking error The returns of the fund are expected to be slightly below the returns of its benchmark index (referred to as “tracking error”) because the fund incurs fees and transaction expenses while the index has no fees or expenses. The risk of tracking error is increased to the extent the fund is unable to fully replicate its index, which could result from changes in the composition of the index or the timing of purchases and redemptions of fund shares.

Futures risk To the extent the fund uses futures, it is exposed to potential volatility and losses greater than direct investments in the contract’s underlying assets.
Risk Lose Money [Text] rr_RiskLoseMoney The fund’s share price fluctuates, which means you could lose money by investing in the fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

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] rr_PerformanceInformationIllustratesVariabilityOfReturns 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.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-225-5132
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress troweprice.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart Table: rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Equity Index 500 Fund

Calendar Year Returns
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
           
    Quarter   Total  
    Ended   Return  
Best Quarter   6/30/09   15.99%  
Worst Quarter   12/31/08   -21.94%  
Average Annual Return: rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Total Returns

Periods ended

December 31, 2011
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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 rr_PerformanceTableNotRelevantToTaxDeferred 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 rr_PerformanceTableNarrativeTextBlock 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] rr_PerformanceTableClosingTextBlock Updated performance information is available through troweprice.com or may be obtained by calling 1-800-225-5132.
T. Rowe Price Equity Index 500 Fund | T. Rowe Price Equity Index 500 Fund
  
Shareholder Fees: rr_ShareholderFeesAbstract  
Maximum sales charge (load) imposed on purchases rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee (as a percentage of amount redeemed on shares held for 90 days or less) rr_RedemptionFeeOverRedemption 0.50%
Maximum account fee rr_MaximumAccountFee 20 [1]
Operating Expenses: rr_OperatingExpensesAbstract  
Management fees rr_ManagementFeesOverAssets 0.10%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.20%
Total annual fund operating expenses rr_ExpensesOverAssets 0.30%
Expense Example: rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 31
3 years rr_ExpenseExampleYear03 97
5 years rr_ExpenseExampleYear05 169
10 years rr_ExpenseExampleYear10 381
Bar Chart Table: rr_BarChartTableAbstract  
02 rr_AnnualReturn2002 (22.21%)
03 rr_AnnualReturn2003 28.31%
04 rr_AnnualReturn2004 10.51%
05 rr_AnnualReturn2005 4.62%
06 rr_AnnualReturn2006 15.41%
07 rr_AnnualReturn2007 5.18%
08 rr_AnnualReturn2008 (37.06%)
09 rr_AnnualReturn2009 26.33%
10 rr_AnnualReturn2010 14.71%
11 rr_AnnualReturn2011 1.87%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 15.99%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (21.94%)
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 1.87%
5 Years rr_AverageAnnualReturnYear05 (0.46%)
10 Years rr_AverageAnnualReturnYear10 2.67%
T. Rowe Price Equity Index 500 Fund | Returns after taxes on distributions | T. Rowe Price Equity Index 500 Fund
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 1.59%
5 Years rr_AverageAnnualReturnYear05 (0.74%)
10 Years rr_AverageAnnualReturnYear10 2.38%
T. Rowe Price Equity Index 500 Fund | Returns after taxes on distributions and sale of fund shares | T. Rowe Price Equity Index 500 Fund
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 1.57%
5 Years rr_AverageAnnualReturnYear05 (0.41%)
10 Years rr_AverageAnnualReturnYear10 2.24%
T. Rowe Price Equity Index 500 Fund | S&P 500 Index
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 2.11%
5 Years rr_AverageAnnualReturnYear05 (0.25%)
10 Years rr_AverageAnnualReturnYear10 2.92%
T. Rowe Price Extended Equity Market Index Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

Extended Equity Market Index Fund

SUMMARY
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to match the performance of the U.S. stocks not included in the Standard & Poor’s 500 Stock Index.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold shares of the fund.
Shareholder Fees: rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

Fees and Expenses of the Fund

Shareholder fees (fees paid directly from your investment)
Operating Expenses: rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

Annual fund operating expenses

(expenses that you pay each year as a

percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 18.9% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 18.90%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The figure shown under “Total annual fund operating expenses” 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: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

Investments, Risks, and Performance

Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The fund seeks to match the performance of the U.S. stocks that are not included in the S&P 500 Index, which are primarily small- and mid-capitalization stocks. The fund uses the S&P Completion Index as its benchmark index to represent this universe.

The fund uses a sampling strategy, investing substantially all of its assets in a group of stocks representative of the S&P Completion Index. The fund does not attempt to fully replicate the index by owning each of the stocks in the index. The index includes approximately 3,700 stocks.

In an attempt to replicate the S&P Index, we select stocks based on industry, size, and other characteristics. For example, if technology stocks made up 15% of the S&P Index, the fund would invest about 15% of its assets in technology stocks with similar characteristics. Several factors are considered in selecting representative stocks, including historical price movement, market capitalization, transaction costs, and others.

Under normal conditions, the fund will invest at least 80% of its net assets (including any borrowings for investment purposes) in stocks that are held in its benchmark index. T. Rowe Price compares the composition of the fund to that of the index. If a material misweighting develops, the portfolio managers seek to rebalance the portfolio in an effort to realign it with its index.

While most assets will be invested in common stocks, the fund may also purchase stock index futures contracts. Futures would typically be used to reduce cash balances in the fund and increase the level of fund assets exposed to common stocks represented in the fund’s benchmark index.

While there is no guarantee, the correlation between the fund and its index is expected to be at least 0.95. A correlation of 1.00 indicates that the returns of the fund and the index will always move in the same direction (but not necessarily by the same amount). A correlation of 0.00 would mean movements in the fund are unrelated to movements in the index.

The fund may sell securities to better align its portfolio with the characteristics of its benchmark or to satisfy redemption requests. However, the fund is not required to sell specific securities that have been removed from its index.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

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:

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.

Small- and mid-cap stock risk Because the fund invests primarily in small- and medium-sized companies, its share price could be more volatile than a fund that invests only in large companies. Small- and medium-sized companies often have less experienced management, narrower product lines, more limited financial resources, and less publicly available information than larger companies. Smaller companies may have limited trading markets and tend to be more sensitive to changes in overall economic conditions.

Index investing risk Because the fund is passively managed and seeks to match the performance of its benchmark index, holdings are generally not reallocated based on changes in market conditions or outlook for a specific security, industry, or market sector. As a result, the fund’s performance may lag the performance of actively managed funds.

Tracking error The returns of the fund are expected to be slightly below the returns of its benchmark index (referred to as “tracking error”) because the fund incurs fees and transaction expenses while the index has no fees or expenses. Increased tracking error could also result from changes in the composition of the index or the timing of purchases and redemptions of fund shares. The fund uses a sampling strategy and does not attempt to fully replicate its benchmark index, which increases the potential for the fund’s performance to deviate from that of its index.

Futures risk To the extent the fund uses futures, it is exposed to potential volatility and losses greater than direct investments in the contract’s underlying assets.
Risk Lose Money [Text] rr_RiskLoseMoney The fund’s share price fluctuates, which means you could lose money by investing in the fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

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] rr_PerformanceInformationIllustratesVariabilityOfReturns 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.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-225-5132
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress troweprice.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart Table: rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Extended Equity Market Index Fund

Calendar Year Returns
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
           
    Quarter   Total  
    Ended   Return  
Best Quarter   6/30/09   21.55%  
Worst Quarter   12/31/08   -26.52%  
Average Annual Return: rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Total Returns

Periods ended

December 31, 2011
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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 rr_PerformanceTableNotRelevantToTaxDeferred 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 rr_PerformanceTableNarrativeTextBlock 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] rr_PerformanceTableClosingTextBlock Updated performance information is available through troweprice.com or may be obtained by calling 1-800-225-5132.
T. Rowe Price Extended Equity Market Index Fund | T. Rowe Price Extended Equity Market Index Fund
  
Shareholder Fees: rr_ShareholderFeesAbstract  
Maximum sales charge (load) imposed on purchases rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee (as a percentage of amount redeemed on shares held for 90 days or less) rr_RedemptionFeeOverRedemption 0.50%
Maximum account fee rr_MaximumAccountFee 20 [1]
Operating Expenses: rr_OperatingExpensesAbstract  
Management fees rr_ManagementFeesOverAssets 0.40%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets none
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.02%
Total annual fund operating expenses rr_ExpensesOverAssets 0.42% [2]
Expense Example: rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 43
3 years rr_ExpenseExampleYear03 135
5 years rr_ExpenseExampleYear05 235
10 years rr_ExpenseExampleYear10 530
Bar Chart Table: rr_BarChartTableAbstract  
02 rr_AnnualReturn2002 (18.12%)
03 rr_AnnualReturn2003 42.85%
04 rr_AnnualReturn2004 18.38%
05 rr_AnnualReturn2005 9.95%
06 rr_AnnualReturn2006 15.76%
07 rr_AnnualReturn2007 4.07%
08 rr_AnnualReturn2008 (38.50%)
09 rr_AnnualReturn2009 36.69%
10 rr_AnnualReturn2010 27.45%
11 rr_AnnualReturn2011 (3.61%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 21.55%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (26.52%)
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.61%)
5 Years rr_AverageAnnualReturnYear05 1.45%
10 Years rr_AverageAnnualReturnYear10 6.60%
T. Rowe Price Extended Equity Market Index Fund | Returns after taxes on distributions | T. Rowe Price Extended Equity Market Index Fund
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.77%)
5 Years rr_AverageAnnualReturnYear05 0.96%
10 Years rr_AverageAnnualReturnYear10 6.22%
T. Rowe Price Extended Equity Market Index Fund | Returns after taxes on distributions and sale of fund shares | T. Rowe Price Extended Equity Market Index Fund
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (2.26%)
5 Years rr_AverageAnnualReturnYear05 1.09%
10 Years rr_AverageAnnualReturnYear10 5.67%
T. Rowe Price Extended Equity Market Index Fund | S&P Completion Index
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.71%)
5 Years rr_AverageAnnualReturnYear05 1.51%
10 Years rr_AverageAnnualReturnYear10 4.54% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2004
T. Rowe Price Extended Equity Market Index Fund | Combined Index Portfolio
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 (3.71%) [4]
5 Years rr_AverageAnnualReturnYear05 1.45% [4]
10 Years rr_AverageAnnualReturnYear10 6.79% [4]
T. Rowe Price Total Equity Market Index Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading

Total Equity Market Index Fund

SUMMARY
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to match the performance of the entire U.S. stock market.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock This table describes the fees and expenses that you may pay if you buy and hold shares of the fund.
Shareholder Fees: rr_ShareholderFeesAbstract  
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption

Fees and Expenses of the Fund

Shareholder fees (fees paid directly from your investment)
Operating Expenses: rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption

Annual fund operating expenses

(expenses that you pay each year as a

percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 6.2% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 6.20%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text] rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees The figure shown under “Total annual fund operating expenses” 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: rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods. The example also assumes that your investment has a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading] rr_StrategyHeading

Investments, Risks, and Performance

Principal Investment Strategies

Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

The fund seeks to match the performance of the entire U.S. stock market. The fund uses the S&P Total Market Index as its benchmark index to represent the U.S. stock market as a whole. Because the largest stocks in the index carry the most weight, large-capitalization stocks make up a substantial majority of the S&P Total Market Index’s value.

The fund uses a sampling strategy, investing substantially all of its assets in a broad spectrum of small-, mid-, and large-capitalization stocks representative of the S&P Total Market Index. The index includes approximately 4,200 stocks.

In an attempt to replicate the S&P Index, we select stocks based on industry, size, and other characteristics. For example, if technology stocks made up 15% of the S&P Index, the fund would invest about 15% of its assets in technology stocks with similar characteristics. Several factors are considered in selecting representative stocks, including historical price movement, market capitalization, transaction costs, and others.

Under normal conditions, the fund will invest at least 80% of its net assets (including any borrowings for investment purposes) in stocks that are held in its benchmark index. T. Rowe Price compares the composition of the fund to that of the index. If a material misweighting develops, the portfolio managers seek to rebalance the portfolio in an effort to realign it with its index.

While most assets will be invested in common stocks, the fund may also purchase stock index futures contracts. Futures would typically be used to reduce cash balances in the fund and increase the level of fund assets exposed to common stocks represented in the fund’s benchmark index.

While there is no guarantee, the correlation between the fund and its index is expected to be at least 0.95. A correlation of 1.00 indicates that the returns of the fund and the index will always move in the same direction (but not necessarily by the same amount). A correlation of 0.00 would mean movements in the fund are unrelated to movements in the index.

The fund may sell securities to better align its portfolio with the characteristics of its benchmark or to satisfy redemption requests. However, the fund is not required to sell specific securities that have been removed from its index.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

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:

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.

Index investing risk Because the fund is passively managed and seeks to match the performance of its benchmark index, holdings are generally not reallocated based on changes in market conditions or outlook for a specific security, industry, or market sector. As a result, the fund’s performance may lag the performance of actively managed funds.

Tracking error The returns of the fund are expected to be slightly below the returns of its benchmark index (referred to as “tracking error”) because the fund incurs fees and transaction expenses while the index has no fees or expenses. Increased tracking error could also result from changes in the composition of the index or the timing of purchases and redemptions of fund shares. The fund uses a sampling strategy and does not attempt to fully replicate its benchmark index, which increases the potential for the fund’s performance to deviate from that of its index.

Futures risk To the extent the fund uses futures, it is exposed to potential volatility and losses greater than direct investments in the contract’s underlying assets.
Risk Lose Money [Text] rr_RiskLoseMoney The fund’s share price fluctuates, which means you could lose money by investing in the fund.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

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] rr_PerformanceInformationIllustratesVariabilityOfReturns 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.
Performance Availability Phone [Text] rr_PerformanceAvailabilityPhone 1-800-225-5132
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress troweprice.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund’s past performance (before and after taxes) is not necessarily an indication of future performance.
Bar Chart Table: rr_BarChartTableAbstract  
Bar Chart [Heading] rr_BarChartHeading

Total Equity Market Index Fund

Calendar Year Returns
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
           
    Quarter   Total  
    Ended   Return  
Best Quarter   6/30/09   16.97%  
Worst Quarter   12/31/08   -22.84%  
Average Annual Return: rr_AverageAnnualReturnAbstract  
Performance Table Heading rr_PerformanceTableHeading

Average Annual Total Returns

Periods ended

December 31, 2011
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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 rr_PerformanceTableNotRelevantToTaxDeferred 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 rr_PerformanceTableNarrativeTextBlock 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] rr_PerformanceTableClosingTextBlock Updated performance information is available through troweprice.com or may be obtained by calling 1-800-225-5132.
T. Rowe Price Total Equity Market Index Fund | T. Rowe Price Total Equity Market Index Fund
  
Shareholder Fees: rr_ShareholderFeesAbstract  
Maximum sales charge (load) imposed on purchases rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum deferred sales charge (load) rr_MaximumDeferredSalesChargeOverOther none
Redemption fee (as a percentage of amount redeemed on shares held for 90 days or less) rr_RedemptionFeeOverRedemption 0.50%
Maximum account fee rr_MaximumAccountFee 20 [1]
Operating Expenses: rr_OperatingExpensesAbstract  
Management fees rr_ManagementFeesOverAssets 0.40%
Distribution and service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets none
Acquired fund fees and expenses rr_AcquiredFundFeesAndExpensesOverAssets 0.01%
Total annual fund operating expenses rr_ExpensesOverAssets 0.41% [2]
Expense Example: rr_ExpenseExampleAbstract  
1 year rr_ExpenseExampleYear01 42
3 years rr_ExpenseExampleYear03 132
5 years rr_ExpenseExampleYear05 230
10 years rr_ExpenseExampleYear10 518
Bar Chart Table: rr_BarChartTableAbstract  
02 rr_AnnualReturn2002 (21.16%)
03 rr_AnnualReturn2003 31.02%
04 rr_AnnualReturn2004 12.22%
05 rr_AnnualReturn2005 6.23%
06 rr_AnnualReturn2006 15.49%
07 rr_AnnualReturn2007 5.25%
08 rr_AnnualReturn2008 (37.16%)
09 rr_AnnualReturn2009 28.76%
10 rr_AnnualReturn2010 16.80%
11 rr_AnnualReturn2011 0.61%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 16.97%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Dec. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (22.84%)
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.61%
5 Years rr_AverageAnnualReturnYear05 0.01%
10 Years rr_AverageAnnualReturnYear10 3.59%
T. Rowe Price Total Equity Market Index Fund | Returns after taxes on distributions | T. Rowe Price Total Equity Market Index Fund
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.38%
5 Years rr_AverageAnnualReturnYear05 (0.26%)
10 Years rr_AverageAnnualReturnYear10 3.32%
T. Rowe Price Total Equity Market Index Fund | Returns after taxes on distributions and sale of fund shares | T. Rowe Price Total Equity Market Index Fund
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.69%
5 Years rr_AverageAnnualReturnYear05 (0.04%)
10 Years rr_AverageAnnualReturnYear10 3.05%
T. Rowe Price Total Equity Market Index Fund | Combined Index Portfolio
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.92% [5]
5 Years rr_AverageAnnualReturnYear05 0.06% [5]
10 Years rr_AverageAnnualReturnYear10 3.79% [5]
T. Rowe Price Total Equity Market Index Fund | S&P Total Market Index
  
Average Annual Return: rr_AverageAnnualReturnAbstract  
1 Year rr_AverageAnnualReturnYear01 0.92%
5 Years rr_AverageAnnualReturnYear05 0.04%
10 Years rr_AverageAnnualReturnYear10 0.92% [3]
Inception Date rr_AverageAnnualReturnInceptionDate Dec. 31, 2004
[1] Subject to certain exceptions, accounts with a balance of less than $10,000 are charged an annual $20 fee.
[2] The figure shown under "Total annual fund operating expenses" 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.
[3] Since 12/31/04.
[4] Combined Index Portfolio is an unmanaged portfolio composed of 100% Dow Jones Wilshire 4500 Completion Index (1/30/98 - 3/31/07), then 100% S&P Completion Index (from 4/1/07 forward). Indices and percentages may vary over time.
[5] Combined Index Portfolio is an unmanaged portfolio composed of 100% Dow Jones Wilshire 5000 Composite Index (1/30/98 - 3/31/07), then 100% S&P Total Market Index (from 4/1/07 forward).