Reportable Segments and Related Information (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2014
item
Dec. 31, 2013
Dec. 31, 2012
Reportable Segments and Related Information                      
Number of reportable segments                 3    
Reportable Segments and Related Information                      
Goodwill $ 20,686       $ 20,686       $ 20,686 $ 20,686  
Total Assets 3,665,607       3,539,575       3,665,607 3,539,575  
Interest income: 27,657 27,511 26,656 26,251 26,885 27,236 27,460 27,115 108,075 108,696 116,916
Interest expense: 1,570 1,600 1,635 1,694 1,881 2,003 2,215 2,532 6,499 8,631 14,770
Other income: 14,739 14,204 15,012 14,986 14,529 15,630 15,783 16,641 58,941 62,583 66,852
Net Income: 7,593 9,109 8,185 7,887 6,920 7,933 7,440 6,433 32,774 28,726 22,357
FirsTech                      
Reportable Segments and Related Information                      
Goodwill 8,992       8,992       8,992 8,992  
Busey Wealth Management                      
Reportable Segments and Related Information                      
Goodwill 11,694       11,694       11,694 11,694  
Operating segments | Busey Bank                      
Reportable Segments and Related Information                      
Total Assets 3,589,419       3,456,555       3,589,419 3,456,555  
Interest income:                 107,766 108,413 116,608
Interest expense:                 5,355 7,448 13,466
Other income:                 32,452 36,774 39,908
Net Income:                 30,764 25,416 19,162
Operating segments | FirsTech                      
Reportable Segments and Related Information                      
Goodwill 8,992       8,992       8,992 8,992  
Total Assets 28,540       27,253       28,540 27,253  
Interest income:                 52 51 62
Other income:                 9,561 8,541 8,522
Net Income:                 1,227 1,000 935
Operating segments | Busey Wealth Management                      
Reportable Segments and Related Information                      
Goodwill 11,694       11,694       11,694 11,694  
Total Assets 31,196       28,548       31,196 28,548  
Interest income:                 287 242 251
Other income:                 18,953 17,799 16,345
Net Income:                 4,681 4,242 3,363
All other                      
Reportable Segments and Related Information                      
Total Assets 16,452       27,219       16,452 27,219  
Interest income:                 (30) (10) (5)
Interest expense:                 1,144 1,183 1,304
Other income:                 (2,025) (531) 2,077
Net Income:                 $ (3,898) $ (1,932) $ (1,103)