| Shareholder Report | 12 Months Ended |
| Aug. 31, 2024 USD ($) Holding |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Vanguard Admiral Funds |
| Entity Central Index Key | 0000891190 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Aug. 31, 2024 |
| C000005732 | |
| Shareholder Report [Line Items] | |
| Fund Name | Treasury Money Market Fund |
| Class Name | Investor Shares |
| Trading Symbol | VUSXX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains important information about Vanguard Treasury Money Market Fund (the "Fund") for the period of September 1, 2023, to August 31, 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. |
| 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 $9 0.09% |
| Expenses Paid, Amount | $ 9 |
| Expense Ratio, Percent | 0.09% |
| AssetsNet | $ 79,936,000,000 |
| Holdings Count | Holding | 31 |
| Advisory Fees Paid, Amount | $ 442,000 |
| Additional Fund Statistics [Text Block] | Fund Statistics (as of August 31, 2024 Fund Net Assets (in millions) $79,936 Number of Portfolio Holdings 31 Total Investment Advisory Fees (in thousands) $442 |
| Holdings [Text Block] | This table reflects the Fund's investments, including short-term investments and other assets and liabilities. Distribution by Effective Maturity % of Net Assets (as of August 31, 2024 1 to 7 Days 19.3% 8 to 30 Days 37.9% 31 to 60 Days 51.7% 61 to 90 Days 5.4% 91 to 180 Days 2.9% Other Assets and Liabilities—Net (17.2%) |
| Material Fund Change [Text Block] | |
| Updated Prospectus Web Address | https://personal1.vanguard.com/ngf-next-gen-form-webapp/fund-literature |
