v3.26.1
Shareholder Report
 6 Months Ended
Jun. 30, 2026
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name T. ROWE PRICE INDEX TRUST, INC.
Entity Central Index Key 0000858581
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2026
Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
C000161835  
Shareholder Report [Line Items]  
Fund Name Mid-Cap Index Fund
Class Name Investor Class
Trading Symbol TRMNX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Mid-Cap Index Fund (the "fund") for the period of January 1, 2026 to June 30, 2026.
Additional Information [Text Block] You can find the fund’s prospectus, financial information on Form N‑CSR (which includes required tax information for dividends), holdings, proxy voting information, and other information atwww.troweprice.com/prospectus. You can also request this information without charge by contacting T. Rowe Price at 1‑800‑638‑5660 or info@troweprice.com or contacting your intermediary.
Material Fund Change Notice [Text Block]  
Additional Information Phone Number 1‑800‑638‑5660
Additional Information Email <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 17.3333px; margin: 0px; overflow: visible; text-align: justify; text-align-last: left; white-space-collapse: preserve-breaks;">info@troweprice.com</span>
Additional Information Website www.troweprice.com/prospectus
Expenses [Text Block]

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Table Summary
 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Mid-Cap Index Fund - Investor Class
$14
0.27%
Expenses Paid, Amount $ 14
Expense Ratio, Percent 0.27%
Updated Performance Information Location [Text Block]

If you invest directly with T. Rowe Price, you can elect to receive future shareholder reports or other important documents through electronic delivery by enrolling at www.troweprice.com/paperless. If you invest through a financial intermediary such as an investment advisor, a bank, retirement plan sponsor or a brokerage firm, please contact that organization and ask if it can provide electronic delivery.

Visit www.troweprice.com/en/us/market-data-disclosures for additional legal notices & disclaimers.
AssetsNet $ 503,746,000
Holdings Count | Holding 526
InvestmentCompanyPortfolioTurnover 35.00%
Additional Fund Statistics [Text Block]

What are some fund statistics?

Fund Statistics

Table Summary
Total Net Assets (000s)
$503,746
Number of Portfolio Holdings
526
Additional Fund Statistics Significance or Limits [Text Block]
Table Summary
Portfolio Turnover Rate
35.0%
Holdings [Text Block]

Sector Allocation (as a % of Net Assets)

Table Summary
Industrials & Business Services
23.6%
Information Technology
20.5
Financials
13.1
Health Care
10.2
Consumer Discretionary
9.3
Communication Services
6.3
Materials
4.8
Real Estate
4.5
Energy
3.4
Other
4.3
Largest Holdings [Text Block]

Top Ten Holdings (as a % of Net Assets)

Table Summary
Space Exploration Technologies
1.6%
Snowflake
1.5
Bloom Energy
1.4
Cloudflare
1.4
Astera Labs
1.3
Spotify Technology
1.3
Rocket Lab
1.0
Cheniere Energy
0.9
NU Holdings
0.8
Ferguson Enterprises
0.8
Material Fund Change [Text Block]
Updated Prospectus Web Address www.troweprice.com/paperless
C000161836  
Shareholder Report [Line Items]  
Fund Name Mid-Cap Index Fund
Class Name I Class
Trading Symbol TRMSX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Mid-Cap Index Fund (the "fund") for the period of January 1, 2026 to June 30, 2026.
Additional Information [Text Block] You can find the fund’s prospectus, financial information on Form N‑CSR (which includes required tax information for dividends), holdings, proxy voting information, and other information atwww.troweprice.com/prospectus. You can also request this information without charge by contacting T. Rowe Price at 1‑800‑638‑5660 or info@troweprice.com or contacting your intermediary.
Material Fund Change Notice [Text Block]  
Additional Information Phone Number 1‑800‑638‑5660
Additional Information Email <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 17.3333px; margin: 0px; overflow: visible; text-align: justify; text-align-last: left; white-space-collapse: preserve-breaks;">info@troweprice.com</span>
Additional Information Website www.troweprice.com/prospectus
Expenses [Text Block]

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Table Summary
 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Mid-Cap Index Fund - I Class
$7
0.14%
Expenses Paid, Amount $ 7
Expense Ratio, Percent 0.14%
Updated Performance Information Location [Text Block]

If you invest directly with T. Rowe Price, you can elect to receive future shareholder reports or other important documents through electronic delivery by enrolling at www.troweprice.com/paperless. If you invest through a financial intermediary such as an investment advisor, a bank, retirement plan sponsor or a brokerage firm, please contact that organization and ask if it can provide electronic delivery.

Visit www.troweprice.com/en/us/market-data-disclosures for additional legal notices & disclaimers.
AssetsNet $ 503,746,000
Holdings Count | Holding 526
InvestmentCompanyPortfolioTurnover 35.00%
Additional Fund Statistics [Text Block]

What are some fund statistics?

Fund Statistics

Table Summary
Total Net Assets (000s)
$503,746
Number of Portfolio Holdings
526
Additional Fund Statistics Significance or Limits [Text Block]
Table Summary
Portfolio Turnover Rate
35.0%
Holdings [Text Block]

Sector Allocation (as a % of Net Assets)

Table Summary
Industrials & Business Services
23.6%
Information Technology
20.5
Financials
13.1
Health Care
10.2
Consumer Discretionary
9.3
Communication Services
6.3
Materials
4.8
Real Estate
4.5
Energy
3.4
Other
4.3
Largest Holdings [Text Block]

Top Ten Holdings (as a % of Net Assets)

Table Summary
Space Exploration Technologies
1.6%
Snowflake
1.5
Bloom Energy
1.4
Cloudflare
1.4
Astera Labs
1.3
Spotify Technology
1.3
Rocket Lab
1.0
Cheniere Energy
0.9
NU Holdings
0.8
Ferguson Enterprises
0.8
Material Fund Change [Text Block]
Updated Prospectus Web Address www.troweprice.com/paperless
C000219328  
Shareholder Report [Line Items]  
Fund Name Mid-Cap Index Fund
Class Name Z Class
Trading Symbol TRSZX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about Mid-Cap Index Fund (the "fund") for the period of January 1, 2026 to June 30, 2026.
Additional Information [Text Block] You can find the fund’s prospectus, financial information on Form N‑CSR (which includes required tax information for dividends), holdings, proxy voting information, and other information atwww.troweprice.com/prospectus. You can also request this information without charge by contacting T. Rowe Price at 1‑800‑638‑5660 or info@troweprice.com or contacting your intermediary.
Material Fund Change Notice [Text Block]  
Additional Information Phone Number 1‑800‑638‑5660
Additional Information Email <span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 13.3333px; font-weight: 400; grid-area: auto; line-height: 17.3333px; margin: 0px; overflow: visible; text-align: justify; text-align-last: left; white-space-collapse: preserve-breaks;">info@troweprice.com</span>
Additional Information Website www.troweprice.com/prospectus
Expenses [Text Block]

What were the fund costs for the last six months? (based on a hypothetical $10,000 investment)

Table Summary
 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
Mid-Cap Index Fund - Z Class
$0
0.00%
Expenses Paid, Amount $ 0
Expense Ratio, Percent 0.00%
Updated Performance Information Location [Text Block]

If you invest directly with T. Rowe Price, you can elect to receive future shareholder reports or other important documents through electronic delivery by enrolling at www.troweprice.com/paperless. If you invest through a financial intermediary such as an investment advisor, a bank, retirement plan sponsor or a brokerage firm, please contact that organization and ask if it can provide electronic delivery.

Visit www.troweprice.com/en/us/market-data-disclosures for additional legal notices & disclaimers.
AssetsNet $ 503,746,000
Holdings Count | Holding 526
InvestmentCompanyPortfolioTurnover 35.00%
Additional Fund Statistics [Text Block]

What are some fund statistics?

Fund Statistics

Table Summary
Total Net Assets (000s)
$503,746
Number of Portfolio Holdings
526
Additional Fund Statistics Significance or Limits [Text Block]
Table Summary
Portfolio Turnover Rate
35.0%
Holdings [Text Block]

Sector Allocation (as a % of Net Assets)

Table Summary
Industrials & Business Services
23.6%
Information Technology
20.5
Financials
13.1
Health Care
10.2
Consumer Discretionary
9.3
Communication Services
6.3
Materials
4.8
Real Estate
4.5
Energy
3.4
Other
4.3
Largest Holdings [Text Block]

Top Ten Holdings (as a % of Net Assets)

Table Summary
Space Exploration Technologies
1.6%
Snowflake
1.5
Bloom Energy
1.4
Cloudflare
1.4
Astera Labs
1.3
Spotify Technology
1.3
Rocket Lab
1.0
Cheniere Energy
0.9
NU Holdings
0.8
Ferguson Enterprises
0.8
Material Fund Change [Text Block]
Updated Prospectus Web Address www.troweprice.com/paperless