Regulatory Capital (Details) - USD ($) $ in Thousands	Oct. 12, 2018	Sep. 30, 2019	Dec. 31, 2018
Total Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 1,020,195	$ 894,572
Minimum Capital Requirement, Amount		595,295	482,638
Minimum To Be Well Capitalized, Amount		$ 744,118	$ 603,297
Total Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		13.71%	14.83%
Minimum Capital Requirement, Ratio (as a percent)		8.00%	8.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 907,230	$ 783,924
Minimum Capital Requirement, Amount		446,471	361,978
Minimum To Be Well Capitalized, Amount		$ 595,295	$ 482,638
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		12.19%	12.99%
Minimum Capital Requirement, Ratio (as a percent)		6.00%	6.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		8.00%	8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 833,230	$ 709,924
Minimum Capital Requirement, Amount		334,854	271,484
Minimum To Be Well Capitalized, Amount		$ 483,677	$ 392,143
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		11.20%	11.77%
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 Average Assets), Amount
Actual, Amount		$ 907,230	$ 783,924
Minimum Capital Requirement, Amount		$ 371,129	$ 302,704
Tier 1 Capital (to Average Assets), Ratio
Actual, Ratio (as a percent)		9.78%	10.36%
Minimum Capital Requirement, Ratio (as a percent)		4.00%	4.00%
Busey Bank
Total Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 883,146	$ 854,351
Minimum Capital Requirement, Amount		507,070	481,701
Minimum To Be Well Capitalized, Amount		$ 633,837	$ 602,126
Total Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		13.93%	14.19%
Minimum Capital Requirement, Ratio (as a percent)		8.00%	8.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		10.00%	10.00%
Tier 1 Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 830,995	$ 803,703
Minimum Capital Requirement, Amount		380,303	361,276
Minimum To Be Well Capitalized, Amount		$ 507,070	$ 481,701
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		13.11%	13.35%
Minimum Capital Requirement, Ratio (as a percent)		6.00%	6.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		8.00%	8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 830,995	$ 803,703
Minimum Capital Requirement, Amount		285,227	270,957
Minimum To Be Well Capitalized, Amount		$ 411,994	$ 391,382
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		13.11%	13.35%
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 Average Assets), Amount
Actual, Amount		$ 830,995	$ 803,703
Minimum Capital Requirement, Amount		298,943	302,232
Minimum To Be Well Capitalized, Amount		$ 373,679	$ 377,789
Tier 1 Capital (to Average Assets), Ratio
Actual, Ratio (as a percent)		11.12%	10.64%
Minimum Capital Requirement, Ratio (as a percent)		4.00%	4.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		5.00%	5.00%
Banc Ed
Total Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 198,244
Minimum Capital Requirement, Amount		87,743
Minimum To Be Well Capitalized, Amount		$ 109,678
Total Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		18.08%
Minimum Capital Requirement, Ratio (as a percent)		8.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		10.00%
Tier 1 Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 197,430
Minimum Capital Requirement, Amount		65,807
Minimum To Be Well Capitalized, Amount		$ 87,743
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		18.00%
Minimum Capital Requirement, Ratio (as a percent)		6.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Amount
Actual, Amount		$ 197,430
Minimum Capital Requirement, Amount		49,356
Minimum To Be Well Capitalized, Amount		$ 71,291
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual, Ratio (as a percent)		18.00%
Minimum Capital Requirement, Ratio (as a percent)		4.50%
Minimum To Be Well Capitalized, Ratio (as a percent)		6.50%
Tier 1 Capital (to Average Assets), Amount
Actual, Amount		$ 197,430
Minimum Capital Requirement, Amount		74,851
Minimum To Be Well Capitalized, Amount		$ 93,563
Tier 1 Capital (to Average Assets), Ratio
Actual, Ratio (as a percent)		10.55%
Minimum Capital Requirement, Ratio (as a percent)		4.00%
Minimum To Be Well Capitalized, Ratio (as a percent)		5.00%
Busey Bank
Regulatory Capital
Distribution received through chartered amendment	$ 40,000