| Document and Entity Information | Jul. 27, 2021 |
| Document and Entity Information [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Jul. 27, 2021 |
| Entity Registrant Name | First Busey Corporation |
| Entity Incorporation, State or Country Code | NV |
| Entity File Number | 0-15950 |
| Entity Tax Identification Number | 37-1078406 |
| Entity Address, Address Line One | 100 W. University Ave. |
| Entity Address, City or Town | Champaign |
| Entity Address, State or Province | IL |
| Entity Address, Postal Zip Code | 61820 |
| City Area Code | 217 |
| Local Phone Number | 365-4544 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000314489 |
| Title of 12(b) Security | Common Stock, $0.001 par value |
| Trading Symbol | BUSE |
| Security Exchange Name | NASDAQ |
