REGULATORY CAPITAL - Schedule of Regulatory Capital Requirements Applicable to Busey and Busey Bank (Details) $ in Thousands	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Common Equity Tier 1 Capital to Risk Weighted Assets, Amount
Actual	$ 1,237,301	$ 1,155,973
Minimum Capital Requirement	394,840	397,331
Minimum To Be Well Capitalized	$ 570,325	$ 573,923
Common Equity Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1410	0.1309
Minimum Capital Requirement	0.0450	0.0450
Minimum To Be Well Capitalized	0.0650	0.0650
Tier 1 Capital to Risk Weighted Assets, Amount
Actual	$ 1,314,301	$ 1,229,973
Minimum Capital Requirement	526,453	529,775
Minimum To Be Well Capitalized	$ 701,938	$ 706,367
Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1498	0.1393
Minimum Capital Requirement	0.0600	0.0600
Minimum To Be Well Capitalized	0.0800	0.0800
Total Capital to Risk Weighted Assets, Amount
Actual	$ 1,625,943	$ 1,540,318
Minimum Capital Requirement	701,938	706,367
Minimum To Be Well Capitalized	$ 877,422	$ 882,958
Total Capital to Risk Weighted Assets, Ratio
Actual	0.1853	0.1744
Minimum Capital Requirement	0.0800	0.0800
Minimum To Be Well Capitalized	0.1000	0.1000
Leverage Ratio of Tier 1 Capital to Average Assets, Amount
Actual	$ 1,314,301	$ 1,229,973
Minimum Capital Requirement	$ 475,348	$ 488,315
Leverage Ratio of Tier 1 Capital to Average Assets, Ratio
Actual	0.1106	0.1008
Minimum Capital Requirement	0.0400	0.0400
Busey Bank
Common Equity Tier 1 Capital to Risk Weighted Assets, Amount
Actual	$ 1,438,296	$ 1,362,962
Minimum Capital Requirement	393,277	396,128
Minimum To Be Well Capitalized	$ 568,067	$ 572,185
Common Equity Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1646	0.1548
Minimum Capital Requirement	0.0450	0.0450
Minimum To Be Well Capitalized	0.0650	0.0650
Tier 1 Capital to Risk Weighted Assets, Amount
Actual	$ 1,438,296	$ 1,362,962
Minimum Capital Requirement	524,369	528,171
Minimum To Be Well Capitalized	$ 699,159	$ 704,228
Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1646	0.1548
Minimum Capital Requirement	0.0600	0.0600
Minimum To Be Well Capitalized	0.0800	0.0800
Total Capital to Risk Weighted Assets, Amount
Actual	$ 1,520,938	$ 1,448,307
Minimum Capital Requirement	699,159	704,228
Minimum To Be Well Capitalized	$ 873,949	$ 880,285
Total Capital to Risk Weighted Assets, Ratio
Actual	0.1740	0.1645
Minimum Capital Requirement	0.0800	0.0800
Minimum To Be Well Capitalized	0.1000	0.1000
Leverage Ratio of Tier 1 Capital to Average Assets, Amount
Actual	$ 1,438,296	$ 1,362,962
Minimum Capital Requirement	473,878	487,103
Minimum To Be Well Capitalized	$ 592,347	$ 608,879
Leverage Ratio of Tier 1 Capital to Average Assets, Ratio
Actual	0.1214	0.1119
Minimum Capital Requirement	0.0400	0.0400
Minimum To Be Well Capitalized	0.0500	0.0500

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-Topic 942
-SubTopic 505
-Name Accounting Standards Codification
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