| Cover | Dec. 19, 2019 |
| Entity Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Dec. 19, 2019 |
| Entity Registrant Name | FactSet Research Systems Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 1-11869 |
| Entity Tax Identification Number | 13-3362547 |
| Entity Address, Address Line One | 45 Glover Avenue |
| Entity Address, City or Town | Norwalk |
| Entity Address, State or Province | CT |
| Entity Address, Postal Zip Code | 06850 |
| City Area Code | 203 |
| Local Phone Number | 810-1000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Title of 12(b) Security | Common Stock, $0.01 Par Value |
| Trading Symbol | FDS |
| Entity Central Index Key | 0001013237 |
| Amendment Flag | false |
| New York Stock Exchange LLC | |
| Entity Information [Line Items] | |
| Security Exchange Name | NYSE |
| The Nasdaq Stock Market | |
| Entity Information [Line Items] | |
| Security Exchange Name | NASDAQ |
