Capital (Details) - USD ($) $ in Thousands			1 Months Ended
	Oct. 22, 2014	Jan. 22, 2013	Jul. 31, 2013	Sep. 30, 2015
Total Capital (to Risk Weighted Assets), Amount
Actual				$ 496,409
Minimum Capital Requirement				232,628
Minimum To Be Well Capitalized				$ 290,785
Total Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)				17.07%
Minimum Capital Requirement (as a percent)				8.00%
Minimum To Be Well Capitalized (as a percent)				10.00%
Tier 1 Capital (to Risk Weighted Assets), Amount
Actual				$ 459,497
Minimum Capital Requirement				174,471
Minimum To Be Well Capitalized				$ 232,628
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)				15.80%
Minimum Capital Requirement (as a percent)				6.00%
Minimum To Be Well Capitalized (as a percent)				8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Amount
Actual				$ 335,084
Minimum Capital Requirement				130,853
Minimum To Be Well Capitalized				$ 189,010
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)				11.52%
Minimum Capital Requirement (as a percent)				4.50%
Minimum To Be Well Capitalized (as a percent)				6.50%
Tier 1 Capital (to Average Assets), Amount
Actual				$ 459,497
Minimum Capital Requirement				$ 155,655
Tier 1 Capital (to Average Assets), Ratio
Actual (as a percent)				11.81%
Minimum Capital Requirement (as a percent)				4.00%
Maximum assets of bank holding companies for inclusion of proceeds of trust preferred securities from Tier 1 capital unless such securities were issued prior to May 19, 2010				$ 15,000,000
Common equity Tier 1 Risk Based Capital to be well capitalized percentage				6.50%
Dodd-Frank Act ("Basel III Rules")
Total Capital (to Risk Weighted Assets), Ratio
Minimum To Be Well Capitalized (as a percent)			10.00%
Tier 1 Capital (to Risk Weighted Assets), Ratio
Minimum To Be Well Capitalized (as a percent)			8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Minimum To Be Well Capitalized (as a percent)			6.50%
Tier 1 Capital (to Average Assets), Ratio
Common equity Tier 1 Risk Based Capital to be well capitalized percentage			6.50%
Tier 1 Leverage Capital to be well capitalized percentage			5.00%
Maximum consolidated assets of bank holding companies			$ 1,000,000
Maximum consolidated assets of bank holding companies to retain the existing treatment for accumulated other comprehensive income which currently does not affect regulatory capital				$ 15,000,000
Busey Bank
Regulatory Capital
Distribution received through chartered amendment	$ 60,000	$ 50,000
Total Capital (to Risk Weighted Assets), Amount
Actual				443,626
Minimum Capital Requirement				230,493
Minimum To Be Well Capitalized				$ 288,116
Total Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)				15.40%
Minimum Capital Requirement (as a percent)				8.00%
Minimum To Be Well Capitalized (as a percent)				10.00%
Tier 1 Capital (to Risk Weighted Assets), Amount
Actual				$ 407,037
Minimum Capital Requirement				172,870
Minimum To Be Well Capitalized				$ 230,493
Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)				14.13%
Minimum Capital Requirement (as a percent)				6.00%
Minimum To Be Well Capitalized (as a percent)				8.00%
Common Equity Tier 1 Capital (to Risk Weighted Assets), Amount
Actual				$ 407,037
Minimum Capital Requirement				129,653
Minimum To Be Well Capitalized				$ 187,276
Common Equity Tier 1 Capital (to Risk Weighted Assets), Ratio
Actual (as a percent)				14.13%
Minimum Capital Requirement (as a percent)				4.50%
Minimum To Be Well Capitalized (as a percent)				6.50%
Tier 1 Capital (to Average Assets), Amount
Actual				$ 407,037
Minimum Capital Requirement				154,322
Minimum To Be Well Capitalized				$ 192,903
Tier 1 Capital (to Average Assets), Ratio
Actual (as a percent)				10.59%
Minimum Capital Requirement (as a percent)				4.00%
Minimum To Be Well Capitalized (as a percent)				5.00%
Common equity Tier 1 Risk Based Capital to be well capitalized percentage				6.50%