REGULATORY CAPITAL - Schedule of Regulatory Capital Requirements Applicable to Busey and Busey Bank (Details) $ in Thousands	Sep. 30, 2024 USD ($)	Dec. 31, 2023 USD ($)
Common Equity Tier 1 Capital to Risk Weighted Assets, Amount
Actual	$ 1,219,574	$ 1,155,973
Minimum Capital Requirement	398,365	397,331
Minimum To Be Well Capitalized	$ 575,416	$ 573,923
Common Equity Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1378	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	$ 1,296,574	$ 1,229,973
Minimum Capital Requirement	531,153	529,775
Minimum To Be Well Capitalized	$ 708,204	$ 706,367
Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1465	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	$ 1,610,247	$ 1,540,318
Minimum Capital Requirement	708,204	706,367
Minimum To Be Well Capitalized	$ 885,255	$ 882,958
Total Capital to Risk Weighted Assets, Ratio
Actual	0.1819	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	$ 1,296,574	$ 1,229,973
Minimum Capital Requirement	$ 472,629	$ 488,315
Leverage Ratio of Tier 1 Capital to Average Assets, Ratio
Actual	0.1097	0.1008
Minimum Capital Requirement	0.0400	0.0400
Busey Bank
Common Equity Tier 1 Capital to Risk Weighted Assets, Amount
Actual	$ 1,425,762	$ 1,362,962
Minimum Capital Requirement	396,739	396,128
Minimum To Be Well Capitalized	$ 573,068	$ 572,185
Common Equity Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1617	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	$ 1,425,762	$ 1,362,962
Minimum Capital Requirement	528,985	528,171
Minimum To Be Well Capitalized	$ 705,314	$ 704,228
Tier 1 Capital to Risk Weighted Assets, Ratio
Actual	0.1617	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	$ 1,510,436	$ 1,448,307
Minimum Capital Requirement	705,314	704,228
Minimum To Be Well Capitalized	$ 881,642	$ 880,285
Total Capital to Risk Weighted Assets, Ratio
Actual	0.1713	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	$ 1,425,762	$ 1,362,962
Minimum Capital Requirement	471,202	487,103
Minimum To Be Well Capitalized	$ 589,003	$ 608,879
Leverage Ratio of Tier 1 Capital to Average Assets, Ratio
Actual	0.1210	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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