DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of interest income (expense) recorded on swap transactions (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Interest Rate Swap \| Cash Flow Hedging
Derivative Financial Instruments
Interest income (expense) on swap transactions	$ (583)	$ (1,067)	$ (758)

Interest income or expense incurred from sales or purchase of securities and other assets, which the entity does not own, to other parties. Trading liabilities includes the fair value of derivative contracts held for trading that are in loss positions.

No definition available.

Name:	buse_InterestIncomeExpenseTradingLiabilities
Namespace Prefix:	buse_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration