v3.25.2
Shareholder Report
6 Months Ended
Jun. 30, 2025
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name T. ROWE PRICE NEW HORIZONS FUND, INC.
Entity Central Index Key 0000080248
Entity Investment Company Type N-1A
Document Period End Date Jun. 30, 2025
C000005478  
Shareholder Report [Line Items]  
Fund Name New Horizons Fund
Class Name Investor Class
Trading Symbol PRNHX
Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about New Horizons Fund (the "fund") for the period of January 1, 2025 to June 30, 2025. 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. 

Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
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)

 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
New Horizons Fund - Investor Class
$39
0.80%
Expenses Paid, Amount $ 39
Expense Ratio, Percent 0.80%
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 $ 14,971,698,000
Holdings Count | Holding 189
InvestmentCompanyPortfolioTurnover 16.70%
Additional Fund Statistics [Text Block]

What are some fund statistics?

Fund Statistics

Total Net Assets (000s)
$14,971,698
Number of Portfolio Holdings
189
Additional Fund Statistics Significance or Limits [Text Block]
Portfolio Turnover Rate
16.7%
Holdings [Text Block]

Sector Allocation (as a % of Net Assets)

Industrials & Business Services
29.0%
Health Care
26.0
Information Technology
25.8
Financials
6.5
Consumer Discretionary
5.0
Materials
2.2
Energy
1.3
Real Estate
0.5
Communication Services
0.0
Other
3.7
Largest Holdings [Text Block]

Top Ten Holdings (as a % of Net Assets)

Dayforce
3.0%
Paylocity Holding
2.6
Teledyne Technologies
2.5
HubSpot
2.5
Insmed
2.4
Argenx
2.3
Datadog
2.3
Monday.com
2.2
Old Dominion Freight Line
2.2
SiteOne Landscape Supply
2.2
Material Fund Change [Text Block]
Updated Prospectus Web Address www.troweprice.com/paperless
C000159684  
Shareholder Report [Line Items]  
Fund Name New Horizons Fund
Class Name I Class
Trading Symbol PRJIX
Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about New Horizons Fund (the "fund") for the period of January 1, 2025 to June 30, 2025. 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. 

Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
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)

 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
New Horizons Fund - I Class
$32
0.66%
Expenses Paid, Amount $ 32
Expense Ratio, Percent 0.66%
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 $ 14,971,698,000
Holdings Count | Holding 189
InvestmentCompanyPortfolioTurnover 16.70%
Additional Fund Statistics [Text Block]

What are some fund statistics?

Fund Statistics

Total Net Assets (000s)
$14,971,698
Number of Portfolio Holdings
189
Additional Fund Statistics Significance or Limits [Text Block]
Portfolio Turnover Rate
16.7%
Holdings [Text Block]

Sector Allocation (as a % of Net Assets)

Industrials & Business Services
29.0%
Health Care
26.0
Information Technology
25.8
Financials
6.5
Consumer Discretionary
5.0
Materials
2.2
Energy
1.3
Real Estate
0.5
Communication Services
0.0
Other
3.7
Largest Holdings [Text Block]

Top Ten Holdings (as a % of Net Assets)

Dayforce
3.0%
Paylocity Holding
2.6
Teledyne Technologies
2.5
HubSpot
2.5
Insmed
2.4
Argenx
2.3
Datadog
2.3
Monday.com
2.2
Old Dominion Freight Line
2.2
SiteOne Landscape Supply
2.2
Material Fund Change [Text Block]
Updated Prospectus Web Address www.troweprice.com/paperless
C000219323  
Shareholder Report [Line Items]  
Fund Name New Horizons Fund
Class Name Z Class
Trading Symbol TRUZX
Annual or Semi-Annual Statement [Text Block]

This semi-annual shareholder report contains important information about New Horizons Fund (the "fund") for the period of January 1, 2025 to June 30, 2025. 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. 

Shareholder Report Annual or Semi-Annual Semi-Annual Shareholder Report
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)

 
Costs of a $10,000 investment
Costs paid as a percentage of a $10,000 investment
New Horizons 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 $ 14,971,698,000
Holdings Count | Holding 189
InvestmentCompanyPortfolioTurnover 16.70%
Additional Fund Statistics [Text Block]

What are some fund statistics?

Fund Statistics

Total Net Assets (000s)
$14,971,698
Number of Portfolio Holdings
189
Additional Fund Statistics Significance or Limits [Text Block]
Portfolio Turnover Rate
16.7%
Holdings [Text Block]

Sector Allocation (as a % of Net Assets)

Industrials & Business Services
29.0%
Health Care
26.0
Information Technology
25.8
Financials
6.5
Consumer Discretionary
5.0
Materials
2.2
Energy
1.3
Real Estate
0.5
Communication Services
0.0
Other
3.7
Largest Holdings [Text Block]

Top Ten Holdings (as a % of Net Assets)

Dayforce
3.0%
Paylocity Holding
2.6
Teledyne Technologies
2.5
HubSpot
2.5
Insmed
2.4
Argenx
2.3
Datadog
2.3
Monday.com
2.2
Old Dominion Freight Line
2.2
SiteOne Landscape Supply
2.2
Material Fund Change [Text Block]
Updated Prospectus Web Address www.troweprice.com/paperless