0000001 - Document - Cover Page link:presentationLink link:calculationLink link:definitionLink 0000002 - Document - Audit Information link:presentationLink link:calculationLink link:definitionLink 0000003 - Statement - CONSOLIDATED BALANCE SHEETS link:presentationLink link:calculationLink link:definitionLink 0000004 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 0000005 - Statement - CONSOLIDATED STATEMENTS OF INCOME link:presentationLink link:calculationLink link:definitionLink 0000006 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) link:presentationLink link:calculationLink link:definitionLink 0000007 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 0000008 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY link:presentationLink link:calculationLink link:definitionLink 0000009 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 0000010 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS link:presentationLink link:calculationLink link:definitionLink 0000011 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES link:presentationLink link:calculationLink link:definitionLink 0000012 - Disclosure - DEBT SECURITIES link:presentationLink link:calculationLink link:definitionLink 0000013 - Disclosure - PORTFOLIO LOANS link:presentationLink link:calculationLink link:definitionLink 0000014 - Disclosure - OTHER REAL ESTATE OWNED AND OTHER REPOSSESSED ASSETS link:presentationLink link:calculationLink link:definitionLink 0000015 - Disclosure - PREMISES AND EQUIPMENT link:presentationLink link:calculationLink link:definitionLink 0000016 - Disclosure - LEASES link:presentationLink link:calculationLink link:definitionLink 0000017 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS link:presentationLink link:calculationLink link:definitionLink 0000018 - Disclosure - DEPOSITS link:presentationLink link:calculationLink link:definitionLink 0000019 - Disclosure - BORROWINGS link:presentationLink link:calculationLink link:definitionLink 0000020 - Disclosure - JUNIOR SUBORDINATED DEBT OWED TO UNCOLSOLIDATED TRUSTS link:presentationLink link:calculationLink link:definitionLink 0000021 - Disclosure - REGULATORY CAPITAL link:presentationLink link:calculationLink link:definitionLink 0000022 - Disclosure - INCOME TAXES link:presentationLink link:calculationLink link:definitionLink 0000023 - Disclosure - EMPLOYEE BENEFIT PLANS link:presentationLink link:calculationLink link:definitionLink 0000024 - Disclosure - STOCK-BASED COMPENSATION link:presentationLink link:calculationLink link:definitionLink 0000025 - Disclosure - TRANSACTIONS WITH RELATED PARTIES link:presentationLink link:calculationLink link:definitionLink 0000026 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES link:presentationLink link:calculationLink link:definitionLink 0000027 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS link:presentationLink link:calculationLink link:definitionLink 0000028 - Disclosure - FAIR VALUE MEASUREMENTS link:presentationLink link:calculationLink link:definitionLink 0000029 - Disclosure - EARNINGS PER SHARE link:presentationLink link:calculationLink link:definitionLink 0000030 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) link:presentationLink link:calculationLink link:definitionLink 0000031 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION link:presentationLink link:calculationLink link:definitionLink 0000032 - Disclosure - PARENT COMPANY ONLY FINANCIAL INFORMATION link:presentationLink link:calculationLink link:definitionLink 0000033 - Disclosure - ACQUISITIONS link:presentationLink link:calculationLink link:definitionLink 9954471 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES (Policies) link:presentationLink link:calculationLink link:definitionLink 9954472 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954473 - Disclosure - DEBT SECURITIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954474 - Disclosure - PORTFOLIO LOANS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954475 - Disclosure - OTHER REAL ESTATE OWNED AND OTHER REPOSSESSED ASSETS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954476 - Disclosure - PREMISES AND EQUIPMENT (Tables) link:presentationLink link:calculationLink link:definitionLink 9954477 - Disclosure - LEASES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954478 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954479 - Disclosure - DEPOSITS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954480 - Disclosure - BORROWINGS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954481 - Disclosure - REGULATORY CAPITAL (Tables) link:presentationLink link:calculationLink link:definitionLink 9954482 - Disclosure - INCOME TAXES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954483 - Disclosure - EMPLOYEE BENEFIT PLANS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954484 - Disclosure - STOCK-BASED COMPENSATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9954485 - Disclosure - TRANSACTIONS WITH RELATED PARTIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954486 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954487 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954488 - Disclosure - FAIR VALUE MEASUREMENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954489 - Disclosure - EARNINGS PER SHARE (Tables) link:presentationLink link:calculationLink link:definitionLink 9954490 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables) link:presentationLink link:calculationLink link:definitionLink 9954491 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9954492 - Disclosure - PARENT COMPANY ONLY FINANCIAL INFORMATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9954493 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Trust Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9954494 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9954495 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Loan Servicing (Details) link:presentationLink link:calculationLink link:definitionLink 9954496 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Portfolio Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954497 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Schedule of Estimated Useful Lives for Premises and Equipment (Details) link:presentationLink link:calculationLink link:definitionLink 9954498 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Other Intangibles (Details) link:presentationLink link:calculationLink link:definitionLink 9954499 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Cash Surrender Value of Bank Owned Life Insurance (Details) link:presentationLink link:calculationLink link:definitionLink 9954500 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - FHLB Stock (Details) link:presentationLink link:calculationLink link:definitionLink 9954501 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Schedule of Impact of the Busey's other asset investments (Details) link:presentationLink link:calculationLink link:definitionLink 9954502 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Other Asset Investments (Details) link:presentationLink link:calculationLink link:definitionLink 9954503 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Income Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 9954504 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Stock-Based Employee Compensation (Details) link:presentationLink link:calculationLink link:definitionLink 9954505 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Segment Disclosure (Details) link:presentationLink link:calculationLink link:definitionLink 9954506 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Off Balance Sheet Arrangements (Details) link:presentationLink link:calculationLink link:definitionLink 9954507 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES - Recently Issued Accounting Standards Not Yet Adopted (Details) link:presentationLink link:calculationLink link:definitionLink 9954508 - Disclosure - DEBT SECURITIES - Schedule of Amortized Cost, Unrealized Gains and Losses, and Fair Values of Securities Classified as AFS and HTM (Details) link:presentationLink link:calculationLink link:definitionLink 9954509 - Disclosure - DEBT SECURITIES - Schedule of Maturity of Debt Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9954510 - Disclosure - DEBT SECURITIES - Schedule of Gains and Losses on Debt Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9954511 - Disclosure - DEBT SECURITIES - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954512 - Disclosure - DEBT SECURITIES - Schedule of Debt Securities in an Unrealized Loss Position (Details) link:presentationLink link:calculationLink link:definitionLink 9954513 - Disclosure - DEBT SECURITIES - Schedule of Additional Information About Debt Securities Unrealized Loss Position (Details) link:presentationLink link:calculationLink link:definitionLink 9954514 - Disclosure - PORTFOLIO LOANS - Schedule of Distribution of Portfolio Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954515 - Disclosure - PORTFOLIO LOANS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954516 - Disclosure - PORTFOLIO LOANS - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) link:presentationLink link:calculationLink link:definitionLink 9954517 - Disclosure - PORTFOLIO LOANS - Schedule of Risk Grades Segregated by Category of Portfolio Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954518 - Disclosure - PORTFOLIO LOANS - Schedule of Risk Grades of Portfolio Loans, Further Sorted by Origination Year (Details) link:presentationLink link:calculationLink link:definitionLink 9954519 - Disclosure - PORTFOLIO LOANS -Schedule of Portfolio Loans that are Past Due and Still Accruing or on a Non-accrual Status (Details) link:presentationLink link:calculationLink link:definitionLink 9954520 - Disclosure - PORTFOLIO LOANS - Disaggregated by Class of Financing Receivable and Type of Concession Granted (Details) link:presentationLink link:calculationLink link:definitionLink 9954521 - Disclosure - PORTFOLIO LOANS - Schedule of the Effects of Loan Modifications (Details) link:presentationLink link:calculationLink link:definitionLink 9954522 - Disclosure - PORTFOLIO LOANS - Schedule of Amortized Cost Basis of Financing Receivables (Details) link:presentationLink link:calculationLink link:definitionLink 9954523 - Disclosure - PORTFOLIO LOANS - Schedule of Loan Modifications made to Borrowers Experiencing Financial Difficulty (Details) link:presentationLink link:calculationLink link:definitionLink 9954524 - Disclosure - PORTFOLIO LOANS - Schedule of TDR Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954525 - Disclosure - PORTFOLIO LOANS - Schedule of TDRs (Details) link:presentationLink link:calculationLink link:definitionLink 9954526 - Disclosure - PORTFOLIO LOANS - Schedule of Details of Impaired Loans, Segregated by Category (Details) link:presentationLink link:calculationLink link:definitionLink 9954527 - Disclosure - PORTFOLIO LOANS - Schedule of Activity on the Allowance for Loan Losses (Details) link:presentationLink link:calculationLink link:definitionLink 9954528 - Disclosure - PORTFOLIO LOANS - Schedule of Allowance for Loan Losses and Recorded Investments in Portfolio Loans, by Category (Details) link:presentationLink link:calculationLink link:definitionLink 9954529 - Disclosure - OTHER REAL ESTATE OWNED AND OTHER REPOSSESSED ASSETS - Schedule of OREO and Other Repossessed Assets Balances (Details) link:presentationLink link:calculationLink link:definitionLink 9954530 - Disclosure - OTHER REAL ESTATE OWNED AND OTHER REPOSSESSED ASSETS - Schedule of Activity Related to OREO and Other Repossessed Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9954531 - Disclosure - OTHER REAL ESTATE OWNED AND OTHER REPOSSESSED ASSETS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954532 - Disclosure - OTHER REAL ESTATE OWNED AND OTHER REPOSSESSED ASSETS - Schedule of Expenses Related to OREO and Other Repossessed Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9954533 - Disclosure - PREMISES AND EQUIPMENT - Schedule of premises and equipment, net (Details) link:presentationLink link:calculationLink link:definitionLink 9954534 - Disclosure - PREMISES AND EQUIPMENT - Schedule of depreciation expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954535 - Disclosure - LEASES - Schedule of Lease-Related Balances (Details) link:presentationLink link:calculationLink link:definitionLink 9954536 - Disclosure - LEASES - Schedule of Lease Cost and Other Lease Information (Details) link:presentationLink link:calculationLink link:definitionLink 9954537 - Disclosure - LEASES - Schedule of Future Undiscounted Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9954537 - Disclosure - LEASES - Schedule of Future Undiscounted Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9954538 - Disclosure - LEASES - Schedule of Busey as the Lessor (Details) link:presentationLink link:calculationLink link:definitionLink 9954539 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954540 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Carrying Amount of Goodwill by Operating Segment (Details) link:presentationLink link:calculationLink link:definitionLink 9954541 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Other Intangible Asset Disclosures (Details) link:presentationLink link:calculationLink link:definitionLink 9954542 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Amortization Expense Relating to Intangible Assets (Details) link:presentationLink link:calculationLink link:definitionLink 9954543 - Disclosure - GOODWILL AND OTHER INTANGIBLE ASSETS - Schedule of Estimated Amortization Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954544 - Disclosure - DEPOSITS - Schedule of Composition of Deposits (Details) link:presentationLink link:calculationLink link:definitionLink 9954545 - Disclosure - DEPOSITS - Schedule of Maturities of time Deposits (Details) link:presentationLink link:calculationLink link:definitionLink 9954546 - Disclosure - BORROWINGS - Schedule of Securities Sold Under Agreements to Repurchase (Details) link:presentationLink link:calculationLink link:definitionLink 9954547 - Disclosure - BORROWINGS - Term Loan (Details) link:presentationLink link:calculationLink link:definitionLink 9954548 - Disclosure - BORROWINGS - Schedule of Short-Term borrowings (Details) link:presentationLink link:calculationLink link:definitionLink 9954549 - Disclosure - BORROWINGS - Schedule of Long-Term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 9954550 - Disclosure - BORROWINGS - Subordinate Notes (Details) link:presentationLink link:calculationLink link:definitionLink 9954551 - Disclosure - BORROWINGS - Schedule of Unamortized Debt Issuance Cost (Details) link:presentationLink link:calculationLink link:definitionLink 9954552 - Disclosure - JUNIOR SUBORDINATED DEBT OWED TO UNCOLSOLIDATED TRUSTS (Details) link:presentationLink link:calculationLink link:definitionLink 9954553 - Disclosure - REGULATORY CAPITAL - Capital Amounts and Ratios (Details) link:presentationLink link:calculationLink link:definitionLink 9954554 - Disclosure - REGULATORY CAPITAL - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954555 - Disclosure - INCOME TAXES - Schedule of the Components of Income Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 9954556 - Disclosure - INCOME TAXES - Schedule of the Reconciliation of Federal and State Income Taxes at Statutory rates to the Income Taxes Included in the Statements of Income (Details) link:presentationLink link:calculationLink link:definitionLink 9954557 - Disclosure - INCOME TAXES - Schedule of the Deferred Tax Assets and Liabilities (Details) link:presentationLink link:calculationLink link:definitionLink 9954558 - Disclosure - INCOME TAXES - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954559 - Disclosure - EMPLOYEE BENEFIT PLANS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954560 - Disclosure - EMPLOYEE BENEFIT PLANS - Schedule of expenses related to the employee benefit plans (Details) link:presentationLink link:calculationLink link:definitionLink 9954561 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Changes in, the Company's Stock Option Awards (Details) link:presentationLink link:calculationLink link:definitionLink 9954562 - Disclosure - STOCK-BASED COMPENSATION - 2020 Equity Plan (Details) link:presentationLink link:calculationLink link:definitionLink 9954563 - Disclosure - STOCK-BASED COMPENSATION - Schedule of changes in the Company's RSU, PSU, and DSU awards (Details) link:presentationLink link:calculationLink link:definitionLink 9954564 - Disclosure - STOCK-BASED COMPENSATION - 2021 Employee Stock Purchase Plan (Details) link:presentationLink link:calculationLink link:definitionLink 9954565 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954566 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Unamortized Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954567 - Disclosure - TRANSACTIONS WITH RELATED PARTIES (Details) link:presentationLink link:calculationLink link:definitionLink 9954568 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES (Details) link:presentationLink link:calculationLink link:definitionLink 9954569 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of financial instruments owned and pledged as collateral (Details) link:presentationLink link:calculationLink link:definitionLink 9954570 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954571 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Summary of the interest-rate swaps designated as cash flow hedges (Details) link:presentationLink link:calculationLink link:definitionLink 9954572 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Reclassification of unrealized gains and losses from OCI (Details) link:presentationLink link:calculationLink link:definitionLink 9954573 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of interest income (expense) recorded on swap transactions (Details) link:presentationLink link:calculationLink link:definitionLink 9954574 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Net Gains (Losses) Recorded in Accumulated Other Comprehensive Income (Loss) (Details) link:presentationLink link:calculationLink link:definitionLink 9954575 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Interest Rate Swaps Not Designated as Hedges (Details) link:presentationLink link:calculationLink link:definitionLink 9954576 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Interest Rate Swaps Recorded in Noninterest Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954577 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Risk Participation Agreement (Details) link:presentationLink link:calculationLink link:definitionLink 9954578 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Mortgage Banking Derivatives (Details) link:presentationLink link:calculationLink link:definitionLink 9954579 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Net Gains (Losses) Relating to Derivative Instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9954580 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of financial assets and financial liabilities measured at fair value on a recurring basis (Details) link:presentationLink link:calculationLink link:definitionLink 9954581 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of assets and liabilities measured at fair value on a non-recurring basis (Details) link:presentationLink link:calculationLink link:definitionLink 9954582 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of quantitative information about Level 3 fair value measurements (Details) link:presentationLink link:calculationLink link:definitionLink 9954583 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of estimated fair values of financial instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9954584 - Disclosure - EARNINGS PER SHARE - Schedule of computation of earnings per common share (Details) link:presentationLink link:calculationLink link:definitionLink 9954585 - Disclosure - EARNINGS PER SHARE - Schedule of average shares excluded from computation of diluted earnings per common share (Details) link:presentationLink link:calculationLink link:definitionLink 9954586 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) link:presentationLink link:calculationLink link:definitionLink 9954587 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION (Details) link:presentationLink link:calculationLink link:definitionLink 9954588 - Disclosure - PARENT COMPANY ONLY FINANCIAL INFORMATION - Balance Sheets (Details) link:presentationLink link:calculationLink link:definitionLink 9954589 - Disclosure - PARENT COMPANY ONLY FINANCIAL INFORMATION - Statements of Income (Details) link:presentationLink link:calculationLink link:definitionLink 9954590 - Disclosure - PARENT COMPANY ONLY FINANCIAL INFORMATION - Statements of Cash Flows (Details) link:presentationLink link:calculationLink link:definitionLink 9954591 - Disclosure - ACQUISITIONS (Details) link:presentationLink link:calculationLink link:definitionLink