| Shareholder Report | 12 Months Ended |
| Sep. 30, 2024 USD ($) Holding | Sep. 30, 2023 |
| Shareholder Report [Line Items] | | |
| Document Type | N-CSR | |
| Amendment Flag | false | |
| Registrant Name | Vanguard Quantitative Funds | |
| Entity Central Index Key | 0000799127 | |
| Entity Investment Company Type | N-1A | |
| Document Period End Date | Sep. 30, 2024 | |
| C000007980 | | |
| Shareholder Report [Line Items] | | |
| Fund Name | Growth and Income Fund | |
| Class Name | Admiral™ Shares | |
| Trading Symbol | VGIAX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Vanguard Growth and Income Fund (the "Fund") for the period of October 1, 2023, to September 30, 2024. | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature. You can also request this information by contacting us at 800-662-7447. The report describes changes to the Fund that occurred during the reporting period. | |
| Material Fund Change Notice [Text Block] | The report describes changes to the Fund that occurred during the reporting period. | |
| Additional Information Phone Number | 800-662-7447 | |
| Additional Information Website | https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Share Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Admiral Shares $30 0.25% | |
| Expenses Paid, Amount | $ 30 | |
| Expense Ratio, Percent | 0.25% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform during the reporting period? For the 12 months ended September 30, 2024, the Fund performed roughly in line with its benchmark, the S&P 500 Index. U.S. economic growth hovered around 3% on a year-over-year basis during the period, quelling recession fears. The Federal Reserve began cutting interest rates for the first time since early 2020, and the year-over-year rate of consumer price inflation eased to around 2.5%. Even with some negative monthly returns, U.S. stocks finished the period up sharply. Stock selection among industrial companies contributed most to relative performance. The Fund’s underweight stake in consumer staples and its specific holdings in that sector also helped. In an environment where money market yields in excess of 5% paled in comparison to substantial stock gains, the Fund’s modest allocation to cash proved the greatest drag on performance. Stock selection in health care and utilities also detracted somewhat. For the 10 years ended September 30, 2024, the Fund’s average annual return was roughly in line with its benchmark. | |
| Line Graph [Table Text Block] | Admiral Shares S&P 500 Index Dow Jones U.S. Total Stock Market Float Adjusted Index 2014 $50,000 $50,000 $50,000 2014 $52,429 $52,466 $52,614 2015 $53,230 $52,965 $53,561 2015 $53,225 $53,112 $53,625 2015 $50,157 $49,693 $49,727 2015 $53,493 $53,192 $52,846 2016 $54,230 $53,909 $53,329 2016 $55,551 $55,233 $54,723 2016 $57,636 $57,361 $57,150 2016 $59,975 $59,554 $59,514 2017 $63,141 $63,167 $62,962 2017 $64,735 $65,117 $64,856 2017 $67,900 $68,035 $67,818 2017 $72,450 $72,556 $72,109 2018 $71,952 $72,005 $71,673 2018 $74,540 $74,478 $74,449 2018 $80,566 $80,220 $79,740 2018 $69,107 $69,375 $68,290 2019 $78,309 $78,843 $77,878 2019 $81,199 $82,236 $81,062 2019 $82,434 $83,633 $81,983 2019 $89,680 $91,218 $89,391 2020 $71,412 $73,341 $70,654 2020 $86,711 $88,408 $86,261 2020 $94,134 $96,302 $94,089 2020 $105,893 $108,001 $107,976 2021 $113,226 $114,670 $114,939 2021 $122,718 $124,473 $124,465 2021 $122,695 $125,198 $124,318 2021 $136,721 $139,004 $135,680 2022 $131,386 $132,611 $128,354 2022 $110,657 $111,260 $106,744 2022 $105,703 $105,827 $101,873 2022 $113,329 $113,829 $109,183 2023 $120,662 $122,363 $117,093 2023 $130,918 $133,060 $126,920 2023 $126,770 $128,704 $122,744 2023 $141,392 $143,752 $137,635 2024 $158,976 $158,926 $151,462 2024 $165,504 $165,734 $156,368 2024 $172,654 $175,490 $166,000 | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Admiral Shares 36.19% 15.93% 13.19% S&P 500 Index 36.35% 15.98% 13.38% Dow Jones U.S. Total Stock Market Float Adjusted Index 35.24% 15.15% 12.75% | |
| Material Change Date | | Sep. 30, 2023 |
| AssetsNet | $ 15,666,000,000 | |
| Holdings Count | Holding | 758 | |
| Advisory Fees Paid, Amount | $ 16,421,000 | |
| InvestmentCompanyPortfolioTurnover | 84% | |
| Additional Fund Statistics [Text Block] | Fund Statistics (as of September 30, 2024 Fund Net Assets (in millions) $15,666 Number of Portfolio Holdings 758 Portfolio Turnover Rate 84% Total Investment Advisory Fees (in thousands) $16,421 | |
| Holdings [Text Block] | This table reflects the Fund's investments, including short-term investments, derivatives and other assets and liabilities. Portfolio Composition % of Net Assets (as of September 30, 2024 Communication Services 8.9% Consumer Discretionary 12.3% Consumer Staples 4.5% Energy 2.4% Financials 12.4% Health Care 11.6% Industrials 7.9% Information Technology 30.8% Materials 2.1% Other 0.5% Real Estate 2.3% Utilities 2.6% Other Assets and Liabilities—Net 1.7% | |
| Material Fund Change [Text Block] | How has the Fund changed? Effective August 28, 2024, the contractual fee waiver in place with Wellington Management Company LLP to waive 0.03% of the management fee on its portion of the Fund's assets expired. This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available by January 31, 2025 at https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature or upon request at 800-662-7447. | |
| Material Fund Change Expenses [Text Block] | Effective August 28, 2024, the contractual fee waiver in place with Wellington Management Company LLP to waive 0.03% of the management fee on its portion of the Fund's assets expired. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available by January 31, 2025 at https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature or upon request at 800-662-7447. | |
| Updated Prospectus Web Address | https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature | |
| C000007979 | | |
| Shareholder Report [Line Items] | | |
| Fund Name | Growth and Income Fund | |
| Class Name | Investor Shares | |
| Trading Symbol | VQNPX | |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Vanguard Growth and Income Fund (the "Fund") for the period of October 1, 2023, to September 30, 2024. | |
| Shareholder Report Annual or Semi-Annual | Annual Shareholder Report | |
| Additional Information [Text Block] | You can find additional information about the Fund at https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature. You can also request this information by contacting us at 800-662-7447. The report describes changes to the Fund that occurred during the reporting period. | |
| Material Fund Change Notice [Text Block] | The report describes changes to the Fund that occurred during the reporting period. | |
| Additional Information Phone Number | 800-662-7447 | |
| Additional Information Website | https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature | |
| Expenses [Text Block] | What were the Fund costs for the last year? (based on a hypothetical $10,000 investment) Share Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Investor Shares $41 0.35% | |
| Expenses Paid, Amount | $ 41 | |
| Expense Ratio, Percent | 0.35% | |
| Factors Affecting Performance [Text Block] | How did the Fund perform during the reporting period? For the 12 months ended September 30, 2024, the Fund performed roughly in line with its benchmark, the S&P 500 Index. U.S. economic growth hovered around 3% on a year-over-year basis during the period, quelling recession fears. The Federal Reserve began cutting interest rates for the first time since early 2020, and the year-over-year rate of consumer price inflation eased to around 2.5%. Even with some negative monthly returns, U.S. stocks finished the period up sharply. Stock selection among industrial companies contributed most to relative performance. The Fund’s underweight stake in consumer staples and its specific holdings in that sector also helped. In an environment where money market yields in excess of 5% paled in comparison to substantial stock gains, the Fund’s modest allocation to cash proved the greatest drag on performance. Stock selection in health care and utilities also detracted somewhat. For the 10 years ended September 30, 2024, the Fund’s average annual return was roughly in line with its benchmark. | |
| Line Graph [Table Text Block] | Investor Shares S&P 500 Index Dow Jones U.S. Total Stock Market Float Adjusted Index 2014 $10,000 $10,000 $10,000 2014 $10,483 $10,493 $10,523 2015 $10,641 $10,593 $10,712 2015 $10,637 $10,622 $10,725 2015 $10,022 $9,939 $9,945 2015 $10,685 $10,638 $10,569 2016 $10,830 $10,782 $10,666 2016 $11,089 $11,047 $10,945 2016 $11,504 $11,472 $11,430 2016 $11,964 $11,911 $11,903 2017 $12,594 $12,633 $12,592 2017 $12,909 $13,023 $12,971 2017 $13,535 $13,607 $13,564 2017 $14,438 $14,511 $14,422 2018 $14,334 $14,401 $14,335 2018 $14,847 $14,896 $14,890 2018 $16,046 $16,044 $15,948 2018 $13,758 $13,875 $13,658 2019 $15,586 $15,769 $15,576 2019 $16,159 $16,447 $16,212 2019 $16,401 $16,727 $16,397 2019 $17,839 $18,244 $17,878 2020 $14,201 $14,668 $14,131 2020 $17,241 $17,682 $17,252 2020 $18,709 $19,260 $18,818 2020 $21,040 $21,600 $21,595 2021 $22,491 $22,934 $22,988 2021 $24,373 $24,895 $24,893 2021 $24,362 $25,040 $24,864 2021 $27,138 $27,801 $27,136 2022 $26,072 $26,522 $25,671 2022 $21,955 $22,252 $21,349 2022 $20,967 $21,165 $20,375 2022 $22,471 $22,766 $21,837 2023 $23,921 $24,473 $23,419 2023 $25,951 $26,612 $25,384 2023 $25,121 $25,741 $24,549 2023 $28,011 $28,750 $27,527 2024 $31,487 $31,785 $30,292 2024 $32,774 $33,147 $31,274 2024 $34,178 $35,098 $33,200 | |
| Average Annual Return [Table Text Block] | 1 Year 5 Years 10 Years Investor Shares 36.05% 15.82% 13.08% S&P 500 Index 36.35% 15.98% 13.38% Dow Jones U.S. Total Stock Market Float Adjusted Index 35.24% 15.15% 12.75% | |
| Material Change Date | | Sep. 30, 2023 |
| AssetsNet | $ 15,666,000,000 | |
| Holdings Count | Holding | 758 | |
| Advisory Fees Paid, Amount | $ 16,421,000 | |
| InvestmentCompanyPortfolioTurnover | 84% | |
| Additional Fund Statistics [Text Block] | Fund Statistics (as of September 30, 2024 Fund Net Assets (in millions) $15,666 Number of Portfolio Holdings 758 Portfolio Turnover Rate 84% Total Investment Advisory Fees (in thousands) $16,421 | |
| Holdings [Text Block] | This table reflects the Fund's investments, including short-term investments, derivatives and other assets and liabilities. Portfolio Composition % of Net Assets (as of September 30, 2024 Communication Services 8.9% Consumer Discretionary 12.3% Consumer Staples 4.5% Energy 2.4% Financials 12.4% Health Care 11.6% Industrials 7.9% Information Technology 30.8% Materials 2.1% Other 0.5% Real Estate 2.3% Utilities 2.6% Other Assets and Liabilities—Net 1.7% | |
| Material Fund Change [Text Block] | How has the Fund changed? Effective August 28, 2024, the contractual fee waiver in place with Wellington Management Company LLP to waive 0.03% of the management fee on its portion of the Fund's assets expired. This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available by January 31, 2025 at https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature or upon request at 800-662-7447. | |
| Material Fund Change Expenses [Text Block] | Effective August 28, 2024, the contractual fee waiver in place with Wellington Management Company LLP to waive 0.03% of the management fee on its portion of the Fund's assets expired. | |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since September 30, 2023. For more complete information, you may review the Fund’s next prospectus, which we expect to be available by January 31, 2025 at https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature or upon request at 800-662-7447. | |
| Updated Prospectus Web Address | https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature | |
