Regulatory Capital (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 01, 2020	Dec. 31, 2021	Dec. 31, 2020
Common Equity Tier 1 Capital to Risk Weighted Assets, Amount
Actual, Amount		$ 995,874	$ 909,033
Minimum Capital Requirement, Amount		378,334	329,071
Minimum To Be Well Capitalized, Amount		$ 546,482	$ 475,325
Common Equity Tier 1 Capital to Risk Weighted Assets, Ratio
Actual, Ratio (as a percent)		11.85%	12.43%
Minimum Capital Requirement, Ratio (as a percent)		4.50%	4.50%
Minimum To Be Well Capitalized, Ratio (as a percent)		6.50%	6.50%
Tier 1 Capital to Risk Weighted Assets, Amount
Actual, Amount		$ 1,069,874	$ 983,033
Minimum Capital Requirement, Amount		504,445	438,761
Minimum To Be Well Capitalized, Amount		$ 672,594	$ 585,015
Tier 1 Capital to Risk Weighted Assets, Ratio
Actual, Ratio (as a percent)		12.73	13.44
Minimum Capital Requirement, Ratio (as a percent)		6.00	6.00
Minimum To Be Well Capitalized, Ratio (as a percent)		8.00	8.00
Total Capital to Risk Weighted Assets, Amount
Actual, Amount		$ 1,320,187	$ 1,245,997
Minimum Capital Requirement, Amount		672,594	585,015
Minimum To Be Well Capitalized, Amount		$ 840,742	$ 731,269
Total Capital to Risk Weighted Assets, Ratio
Actual, Ratio (as a percent)		15.70	17.04
Minimum Capital Requirement, Ratio (as a percent)		8.00	8.00
Minimum To Be Well Capitalized, Ratio (as a percent)		10.00	10.00
Leverage Ratio of Tier 1 Capital to Average Assets, Amount
Actual, Amount		$ 1,069,874	$ 983,033
Minimum Capital Requirement, Amount		$ 502,336	$ 401,717
Leverage Ratio of Tier 1 Capital to Average Assets, Ratio
Actual, Ratio (as a percent)		8.52	9.79
Minimum Capital Requirement, Ratio (as a percent)		4.00	4.00
Busey Bank paid dividends to the Company, amount received		$ 60,000	$ 122,000
Busey Bank
Common Equity Tier 1 Capital to Risk Weighted Assets, Amount
Actual, Amount		1,241,303	1,053,910
Minimum Capital Requirement, Amount		377,096	328,546
Minimum To Be Well Capitalized, Amount		$ 544,695	$ 474,567
Common Equity Tier 1 Capital to Risk Weighted Assets, Ratio
Actual, Ratio (as a percent)		14.81%	14.44%
Minimum Capital Requirement, Ratio (as a percent)		4.50%	4.50%
Minimum To Be Well Capitalized, Ratio (as a percent)		6.50%	6.50%
Tier 1 Capital to Risk Weighted Assets, Amount
Actual, Amount		$ 1,241,303	$ 1,053,910
Minimum Capital Requirement, Amount		502,795	438,062
Minimum To Be Well Capitalized, Amount		$ 670,394	$ 584,082
Tier 1 Capital to Risk Weighted Assets, Ratio
Actual, Ratio (as a percent)		14.81	14.44
Minimum Capital Requirement, Ratio (as a percent)		6.00	6.00
Minimum To Be Well Capitalized, Ratio (as a percent)		8.00	8.00
Total Capital to Risk Weighted Assets, Amount
Actual, Amount		$ 1,306,616	$ 1,131,875
Minimum Capital Requirement, Amount		670,394	584,082
Minimum To Be Well Capitalized, Amount		$ 837,992	$ 730,103
Total Capital to Risk Weighted Assets, Ratio
Actual, Ratio (as a percent)		15.59	15.50
Minimum Capital Requirement, Ratio (as a percent)		8.00	8.00
Minimum To Be Well Capitalized, Ratio (as a percent)		10.00	10.00
Leverage Ratio of Tier 1 Capital to Average Assets, Amount
Actual, Amount		$ 1,241,303	$ 1,053,910
Minimum Capital Requirement, Amount		501,104	400,581
Minimum To Be Well Capitalized, Amount		$ 626,379	$ 500,727
Leverage Ratio of Tier 1 Capital to Average Assets, Ratio
Actual, Ratio (as a percent)		9.91	10.52
Minimum Capital Requirement, Ratio (as a percent)		4.00	4.00
Minimum To Be Well Capitalized, Ratio (as a percent)		5.00	5.00
Subordinated debt | 5.25% fixed-to-floating rate notes due 2030
Regulatory Capital
Proceeds from public offering	$ 125,000