Name:	buse_GainLossOnSaleOfMortgageLoansIncludingFairValueAdjustmentsGross
Namespace Prefix:	buse_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of direct origination costs related to mortgage loans held for sale.

No definition available.

Name:	buse_MortgageLoansHeldForSaleDirectOriginationCosts
Namespace Prefix:	buse_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of provision related to liability for loans sold.

No definition available.

Name:	buse_MortgageLoansHeldForSaleProvisionToLiabilityForLoansSoldChargedToExpense
Namespace Prefix:	buse_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Income from mortgage banking activities (fees and commissions) and servicing real estate mortgages, credit cards, and other financial assets held by others net of any related impairment of capitalized service costs. Also includes any premiums received in lieu of regular servicing fees on such loans only as earned over the life of the loans.

No definition available.

Name:	us-gaap_FeesAndCommissionsMortgageBankingAndServicing
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The gains (losses) included in earnings that represent the difference between the sale price and the carrying value of loans made to finance real estate acquisitions. This element refers to the gain (loss) and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Name:	us-gaap_GainLossOnSaleOfMortgageLoans
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

Name:	us-gaap_LoansReceivableHeldForSaleNetAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount, after allowance for bad debt, of loan receivables held-for-sale that are not part of a disposal group. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522