Junior Subordinated Debt Owed to Unconsolidated Trusts (Details) (USD $)	12 Months Ended
	Dec. 31, 2012
Junior Subordinated Debt Owed to Unconsolidated Trusts
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	$ 15,000,000,000
Trust Preferred Securities
Junior Subordinated Debt Owed to Unconsolidated Trusts
Percentage limit on inclusion of qualifying trust preferred securities in Tier I Capital	25.00%
Transition period for inclusion of qualifying trust preferred securities in Tier I Capital	5 years
Trust preferred securities qualified as Tier I capital (as a percent)	100.00%
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	15,000,000,000
First Busey Statutory Trust II | Trust Preferred Securities
Junior Subordinated Debt Owed to Unconsolidated Trusts
Face value	15,000,000
Base rate	3-mo LIBOR
Annual distribution rate margin (as a percent)	2.65%
First Busey Statutory Trust III | Trust Preferred Securities
Junior Subordinated Debt Owed to Unconsolidated Trusts
Face value	10,000,000
Base rate	3-mo LIBOR
Annual distribution rate margin (as a percent)	1.75%
First Busey Statutory Trust IV | Trust Preferred Securities
Junior Subordinated Debt Owed to Unconsolidated Trusts
Face value	30,000,000
Base rate	3-mo LIBOR
Annual distribution rate margin (as a percent)	1.55%
Term of trust preferred securities	5 years
Fixed coupon rate (as a percent)	6.94%
Junior Subordinated Notes | Trust Preferred Securities
Junior Subordinated Debt Owed to Unconsolidated Trusts
Maximum period to defer payment of interest on the notes and, therefore, distributions on the trust preferred securities	5 years
Junior Subordinated Notes | First Busey Statutory Trust II
Junior Subordinated Debt Owed to Unconsolidated Trusts
Principal balance	15,000,000
Base rate	3-mo LIBOR
Interest rate margin (as a percent)	2.65%
Junior Subordinated Notes | First Busey Statutory Trust III
Junior Subordinated Debt Owed to Unconsolidated Trusts
Principal balance	10,000,000
Base rate	3-mo LIBOR
Interest rate margin (as a percent)	1.75%
Junior Subordinated Notes | First Busey Statutory Trust IV
Junior Subordinated Debt Owed to Unconsolidated Trusts
Principal balance	$ 30,000,000
Base rate	3-mo LIBOR
Interest rate margin (as a percent)	1.55%
Term of debt	5 years
Fixed coupon rate (as a percent)	6.94%