Form N-CSR Cover
| Form N-CSR Cover | 6 Months Ended |
| Jun. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Vanguard Montgomery Funds |
| Entity Central Index Key | 0001409957 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
Shareholder Report
| Shareholder Report | 6 Months Ended |
| Jun. 30, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | Vanguard Montgomery Funds |
| Entity Central Index Key | 0001409957 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
| C000054090 | |
| Shareholder Report [Line Items] | |
| Fund Name | Market Neutral Fund |
| Class Name | Investor Shares |
| Trading Symbol | VMNFX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Vanguard Market Neutral Fund (the "Fund") for the period of January 1, 2024, to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-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. |
| 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 six months? (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 $68 1.33% Footnote Reference Footnote Description Footnote 1 Annualized. |
| Expenses Paid, Amount | $ 68 |
| Expense Ratio, Percent | 1.33% |
| AssetsNet | $ 466,000,000 |
| Holdings Count | Holding | 447 |
| InvestmentCompanyPortfolioTurnover | 51% |
| Additional Fund Statistics [Text Block] | Fund Statistics (as of June 30, 2024) Fund Net Assets (in millions) $466 Number of Portfolio Holdings 447 Portfolio Turnover Rate 51% |
| Holdings [Text Block] | This table reflects the Fund's investments, including short-term investments and other assets and liabilities. Portfolio Composition % of Net Assets (as of June 30, 2024) Long Portfolio Short Portfolio Communication Services 3.0% 3.5% Consumer Discretionary 9.2% 8.9% Consumer Staples 4.9% 5.0% Energy 6.2% 5.9% Financials 18.5% 17.9% Health Care 12.6% 12.8% Industrials 16.5% 16.1% Information Technology 11.9% 12.2% Materials 3.7% 3.7% Real Estate 6.8% 6.9% Utilities 3.2% 3.2% Other Assets and Liabilities—Net 3.5% 3.9% |
| Material Fund Change [Text Block] | |
| Updated Prospectus Web Address | https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature |
| C000054091 | |
| Shareholder Report [Line Items] | |
| Fund Name | Market Neutral Fund |
| Class Name | Institutional Shares |
| Trading Symbol | VMNIX |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about Vanguard Market Neutral Fund (the "Fund") for the period of January 1, 2024, to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-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. |
| 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 six months? (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 Institutional Shares $65 1.27% Footnote Reference Footnote Description Footnote 1 Annualized. |
| Expenses Paid, Amount | $ 65 |
| Expense Ratio, Percent | 1.27% |
| AssetsNet | $ 466,000,000 |
| Holdings Count | Holding | 447 |
| InvestmentCompanyPortfolioTurnover | 51% |
| Additional Fund Statistics [Text Block] | Fund Statistics (as of June 30, 2024) Fund Net Assets (in millions) $466 Number of Portfolio Holdings 447 Portfolio Turnover Rate 51% |
| Holdings [Text Block] | This table reflects the Fund's investments, including short-term investments and other assets and liabilities. Portfolio Composition % of Net Assets (as of June 30, 2024) Long Portfolio Short Portfolio Communication Services 3.0% 3.5% Consumer Discretionary 9.2% 8.9% Consumer Staples 4.9% 5.0% Energy 6.2% 5.9% Financials 18.5% 17.9% Health Care 12.6% 12.8% Industrials 16.5% 16.1% Information Technology 11.9% 12.2% Materials 3.7% 3.7% Real Estate 6.8% 6.9% Utilities 3.2% 3.2% Other Assets and Liabilities—Net 3.5% 3.9% |
| Material Fund Change [Text Block] | |
| Updated Prospectus Web Address | https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature |
Shareholder Report, Holdings (D
| Shareholder Report, Holdings (Details) | Jun. 30, 2024 |
| C000054090 | Communication Services | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3% |
| Percent of Net Short Exposure | 3.50% |
| C000054090 | Consumer Discretionary | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 9.20% |
| Percent of Net Short Exposure | 8.90% |
| C000054090 | Consumer Staples | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 4.90% |
| Percent of Net Short Exposure | 5% |
| C000054090 | Energy | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 6.20% |
| Percent of Net Short Exposure | 5.90% |
| C000054090 | Financials | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 18.50% |
| Percent of Net Short Exposure | 17.90% |
| C000054090 | Health Care | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 12.60% |
| Percent of Net Short Exposure | 12.80% |
| C000054090 | Industrials | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 16.50% |
| Percent of Net Short Exposure | 16.10% |
| C000054090 | Information Technology | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 11.90% |
| Percent of Net Short Exposure | 12.20% |
| C000054090 | Materials | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3.70% |
| Percent of Net Short Exposure | 3.70% |
| C000054090 | Real Estate | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 6.80% |
| Percent of Net Short Exposure | 6.90% |
| C000054090 | Utilities | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3.20% |
| Percent of Net Short Exposure | 3.20% |
| C000054090 | Sector Other Net Line | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3.50% |
| Percent of Net Short Exposure | 3.90% |
| C000054091 | Communication Services | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3% |
| Percent of Net Short Exposure | 3.50% |
| C000054091 | Consumer Discretionary | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 9.20% |
| Percent of Net Short Exposure | 8.90% |
| C000054091 | Consumer Staples | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 4.90% |
| Percent of Net Short Exposure | 5% |
| C000054091 | Energy | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 6.20% |
| Percent of Net Short Exposure | 5.90% |
| C000054091 | Financials | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 18.50% |
| Percent of Net Short Exposure | 17.90% |
| C000054091 | Health Care | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 12.60% |
| Percent of Net Short Exposure | 12.80% |
| C000054091 | Industrials | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 16.50% |
| Percent of Net Short Exposure | 16.10% |
| C000054091 | Information Technology | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 11.90% |
| Percent of Net Short Exposure | 12.20% |
| C000054091 | Materials | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3.70% |
| Percent of Net Short Exposure | 3.70% |
| C000054091 | Real Estate | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 6.80% |
| Percent of Net Short Exposure | 6.90% |
| C000054091 | Utilities | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3.20% |
| Percent of Net Short Exposure | 3.20% |
| C000054091 | Sector Other Net Line | |
| Holdings [Line Items] | |
| Percent of Net Long Exposure | 3.50% |
| Percent of Net Short Exposure | 3.90% |