Capital - (Details) - USD ($) $ in Thousands		6 Months Ended
	Oct. 21, 2016	Jun. 30, 2017	Jan. 01, 2019	Jan. 01, 2017	Jul. 31, 2013
Total Capital (to Risk Weighted Assets), Amount
Actual		$ 685,626
Minimum Capital Requirement with Capital Buffer		391,865
Minimum To Be Well Capitalized		$ 423,638
Total Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		16.18%
Minimum Capital Requirement with Capital Buffer (as a percent)		9.25%
Minimum To Be Well Capitalized (as a percent)		10.00%
Tier 1 Capital (to Risk Weighted Assets), Amount
Actual		$ 576,286
Minimum Capital Requirement with Capital Buffer		307,138
Minimum To Be Well Capitalized		$ 338,911
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		13.60%
Minimum Capital Requirement with Capital Buffer (as a percent)		7.25%
Minimum To Be Well Capitalized (as a percent)		8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Amount
Actual		$ 502,286
Minimum Capital Requirement with Capital Buffer		243,592
Minimum To Be Well Capitalized		$ 275,365
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		11.86%
Minimum Capital Requirement with Capital Buffer (as a percent)		5.75%
Minimum To Be Well Capitalized (as a percent)		6.50%
Tier 1 Capital (to Average Assets), Amount
Actual		$ 576,286
Minimum Capital Requirement with Capital Buffer		$ 210,017
Tier 1 Capital (to Average Assets), Ratio
Actual (as a percent)		10.98%
Minimum Capital Requirement with Capital Buffer (as a percent)		4.00%
Dodd-Frank Act ("Basel III Rules")
Regulatory Capital
Maximum consolidated assets of bank holding companies					$ 1,000,000
Maximum consolidated assets size of bank holding companies potentially unaffected by certain Tier 1 capital restrictions		$ 15,000,000
Common Equity Tier 1 capital conservation buffer of risk weighted assets		2.50%
Tier 1 Capital (to Average Assets), Ratio
Increase in minimum capital requirement ratios				1.25%
Capital buffer requirement period		3 years
Forecast
Total Capital (to Risk Weighted Assets), Ratio
Minimum Capital Requirement with Capital Buffer (as a percent)			10.50%
Tier 1 Capital (to Risk Weighted Assets), Ratio
Minimum Capital Requirement with Capital Buffer (as a percent)			8.50%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Minimum Capital Requirement with Capital Buffer (as a percent)			7.00%
Busey Bank
Regulatory Capital
Distribution received through chartered amendment	$ 30,000
Total Capital (to Risk Weighted Assets), Amount
Actual		$ 585,244
Minimum Capital Requirement with Capital Buffer		388,482
Minimum To Be Well Capitalized		$ 419,980
Total Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		13.94%
Minimum Capital Requirement with Capital Buffer (as a percent)		9.25%
Minimum To Be Well Capitalized (as a percent)		10.00%
Tier 1 Capital (to Risk Weighted Assets), Amount
Actual		$ 535,904
Minimum Capital Requirement with Capital Buffer		304,486
Minimum To Be Well Capitalized		$ 335,984
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		12.76%
Minimum Capital Requirement with Capital Buffer (as a percent)		7.25%
Minimum To Be Well Capitalized (as a percent)		8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Amount
Actual		$ 535,904
Minimum Capital Requirement with Capital Buffer		241,489
Minimum To Be Well Capitalized		$ 272,987
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		12.76%
Minimum Capital Requirement with Capital Buffer (as a percent)		5.75%
Minimum To Be Well Capitalized (as a percent)		6.50%
Tier 1 Capital (to Average Assets), Amount
Actual		$ 535,904
Minimum Capital Requirement with Capital Buffer		209,036
Minimum To Be Well Capitalized		$ 261,295
Tier 1 Capital (to Average Assets), Ratio
Actual (as a percent)		10.25%
Minimum Capital Requirement with Capital Buffer (as a percent)		4.00%
Minimum To Be Well Capitalized (as a percent)		5.00%