Capital - (Details) - USD ($) $ in Thousands		3 Months Ended
	Oct. 21, 2016	Mar. 31, 2017	Jan. 01, 2019	Jan. 01, 2017	Jul. 31, 2013
Total Capital (to Risk Weighted Assets), Amount
Actual		$ 613,980
Minimum Capital Requirement with Capital Buffer		382,037
Minimum To Be Well Capitalized		$ 413,013
Total Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		14.87%
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		$ 565,391
Minimum Capital Requirement with Capital Buffer		299,434
Minimum To Be Well Capitalized		$ 330,410
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		13.69%
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		$ 491,391
Minimum Capital Requirement with Capital Buffer		237,483
Minimum To Be Well Capitalized		$ 268,458
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		11.90%
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		$ 565,391
Minimum Capital Requirement with Capital Buffer		$ 207,159
Tier 1 Capital (to Average Assets), Ratio
Actual (as a percent)		10.92%
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		$ 566,854
Minimum Capital Requirement with Capital Buffer		378,971
Minimum To Be Well Capitalized		$ 409,698
Total Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		13.84%
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		$ 518,265
Minimum Capital Requirement with Capital Buffer		297,032
Minimum To Be Well Capitalized		$ 327,759
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		12.65%
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		$ 518,265
Minimum Capital Requirement with Capital Buffer		235,577
Minimum To Be Well Capitalized		$ 266,304
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)		12.65%
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		$ 518,265
Minimum Capital Requirement with Capital Buffer		206,130
Minimum To Be Well Capitalized		$ 257,662
Tier 1 Capital (to Average Assets), Ratio
Actual (as a percent)		10.06%
Minimum Capital Requirement with Capital Buffer (as a percent)		4.00%
Minimum To Be Well Capitalized (as a percent)		5.00%