Reportable Segments and Related Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 item	Mar. 31, 2014	Dec. 31, 2014
Reportable Segments and Related Information
Number of reportable segments	3
Reportable Segments and Related Information
Goodwill	$ 25,510		$ 20,686
Total Assets	3,937,184		3,665,607
Interest Income	28,263	26,251
Interest Expense	1,593	1,694
Other Income	15,965	14,986
Noninterest Expense	30,547	26,618
Income before income taxes	11,588	11,925
Net Income:	7,761	7,887
Busey Bank
Reportable Segments and Related Information
Noninterest Expense	24,300	21,044
Income before income taxes	11,048	10,954
FirsTech
Reportable Segments and Related Information
Noninterest Expense	1,946	1,872
Income before income taxes	599	528
Busey Wealth Management
Reportable Segments and Related Information
Noninterest Expense	3,135	2,903
Income before income taxes	1,615	1,702
Operating segments
Reportable Segments and Related Information
Goodwill	25,510		20,686
Total Assets	3,937,184		3,665,607
Operating segments | Busey Bank
Reportable Segments and Related Information
Goodwill	4,824
Total Assets	3,859,021		3,589,419
Interest Income	28,189	26,181
Interest Expense	1,310	1,410
Other Income	8,969	8,227
Net Income:	7,278	7,279
Operating segments | FirsTech
Reportable Segments and Related Information
Goodwill	8,992		8,992
Total Assets	28,847		28,540
Interest Income	13	12
Other Income	2,532	2,387
Net Income:	358	309
Operating segments | Busey Wealth Management
Reportable Segments and Related Information
Goodwill	11,694		11,694
Total Assets	31,067		31,196
Interest Income	71	64
Other Income	4,679	4,541
Net Income:	963	1,002
Other
Reportable Segments and Related Information
Total Assets	18,249		16,452
Interest Income	(10)	(6)
Interest Expense	283	284
Other Income	(215)	(169)
Noninterest Expense	1,166	799
Income before income taxes	(1,674)	(1,259)
Net Income:	$ (838)	$ (703)