| Document and Entity Information | Apr. 15, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | VARIAN MEDICAL SYSTEMS INC |
| Amendment Flag | false |
| Entity Central Index Key | 0000203527 |
| Current Fiscal Year End Date | --10-01 |
| Document Type | 8-K |
| Document Period End Date | Apr. 15, 2021 |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 1-7598 |
| Entity Tax Identification Number | 94-2359345 |
| Entity Address, Address Line One | 3100 Hansen Way |
| Entity Address, City or Town | Palo Alto |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 94304-1030 |
| City Area Code | (650) |
| Local Phone Number | 493-4000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common Stock, $1 par value |
| Trading Symbol | VAR |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
