0000001 - Document - Cover Page link:presentationLink link:calculationLink link:definitionLink 9952151 - Statement - CONSOLIDATED BALANCE SHEETS (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952152 - Statement - CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952153 - Statement - CONSOLIDATED STATEMENTS OF INCOME (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952154 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952155 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952156 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952157 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952158 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952159 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES link:presentationLink link:calculationLink link:definitionLink 9952160 - Disclosure - MERGERS AND ACQUISITIONS link:presentationLink link:calculationLink link:definitionLink 9952161 - Disclosure - DEBT SECURITIES link:presentationLink link:calculationLink link:definitionLink 9952162 - Disclosure - PORTFOLIO LOANS link:presentationLink link:calculationLink link:definitionLink 9952163 - Disclosure - LEASES link:presentationLink link:calculationLink link:definitionLink 9952164 - Disclosure - DEPOSITS link:presentationLink link:calculationLink link:definitionLink 9952165 - Disclosure - BORROWINGS link:presentationLink link:calculationLink link:definitionLink 9952166 - Disclosure - REGULATORY CAPITAL link:presentationLink link:calculationLink link:definitionLink 9952167 - Disclosure - TAX CREDIT AND OTHER INVESTMENTS IN UNCONSOLIDATED ENTITIES link:presentationLink link:calculationLink link:definitionLink 9952168 - Disclosure - STOCK-BASED COMPENSATION link:presentationLink link:calculationLink link:definitionLink 9952169 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES link:presentationLink link:calculationLink link:definitionLink 9952170 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS link:presentationLink link:calculationLink link:definitionLink 9952171 - Disclosure - FAIR VALUE MEASUREMENTS link:presentationLink link:calculationLink link:definitionLink 9952172 - Disclosure - EARNINGS PER COMMON SHARE link:presentationLink link:calculationLink link:definitionLink 9952173 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) link:presentationLink link:calculationLink link:definitionLink 9952174 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION link:presentationLink link:calculationLink link:definitionLink 9954471 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES (Policies) link:presentationLink link:calculationLink link:definitionLink 9954472 - Disclosure - MERGERS AND ACQUISITIONS (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 - LEASES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954476 - Disclosure - DEPOSITS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954477 - Disclosure - BORROWINGS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954478 - Disclosure - REGULATORY CAPITAL (Tables) link:presentationLink link:calculationLink link:definitionLink 9954479 - Disclosure - TAX CREDIT AND OTHER INVESTMENTS IN UNCONSOLIDATED ENTITIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954480 - Disclosure - STOCK-BASED COMPENSATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9954481 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9954482 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954483 - Disclosure - FAIR VALUE MEASUREMENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 9954484 - Disclosure - EARNINGS PER COMMON SHARE (Tables) link:presentationLink link:calculationLink link:definitionLink 9954485 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables) link:presentationLink link:calculationLink link:definitionLink 9954486 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9954487 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES (Details) link:presentationLink link:calculationLink link:definitionLink 9954488 - Disclosure - MERGERS AND ACQUISITIONS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954489 - Disclosure - MERGERS AND ACQUISITIONS - Schedule of Estimated Acquisition-date Fair Values of the Assets Acquired and Liabilities Assumed (Details) link:presentationLink link:calculationLink link:definitionLink 9954490 - Disclosure - MERGERS AND ACQUISITIONS - Schedule of Reconciliation Between the Purchase Price and the Fair Value (Details) link:presentationLink link:calculationLink link:definitionLink 9954491 - Disclosure - DEBT SECURITIES - Schedule of Amortized Cost, Unrealized or Unrecognized Gains and Losses, and Fair Values of Securities Classified as AFS and HTM (Details) link:presentationLink link:calculationLink link:definitionLink 9954492 - Disclosure - DEBT SECURITIES - Schedule of Maturity of Debt Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9954493 - Disclosure - DEBT SECURITIES - Schedule of Realized Gains and Losses on Debt Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9954494 - Disclosure - DEBT SECURITIES - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954495 - Disclosure - DEBT SECURITIES - Schedule of Debt Securities in an Unrealized or Unrecognized Loss Position (Details) link:presentationLink link:calculationLink link:definitionLink 9954496 - Disclosure - DEBT SECURITIES - Schedule of Additional Information on Debt Securities In Unrealized or Unrecognized Loss Position (Details) link:presentationLink link:calculationLink link:definitionLink 9954497 - Disclosure - PORTFOLIO LOANS - Schedule of Distribution of Portfolio Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954498 - Disclosure - PORTFOLIO LOANS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954499 - Disclosure - PORTFOLIO LOANS - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) link:presentationLink link:calculationLink link:definitionLink 9954500 - Disclosure - PORTFOLIO LOANS - Schedule of Risk Grades Segregated by Category and Class of Portfolio Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954501 - Disclosure - PORTFOLIO LOANS - Schedule of Risk Grades of Portfolio Loans, Further Sorted by Origination (Details) link:presentationLink link:calculationLink link:definitionLink 9954502 - Disclosure - PORTFOLIO LOANS - Schedule of Past Due and Non-accrual Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954503 - Disclosure - PORTFOLIO LOANS - Schedule of Loan Modifications for Borrowers Experiencing Financial Difficulty (Details) link:presentationLink link:calculationLink link:definitionLink 9954504 - Disclosure - PORTFOLIO LOANS - Schedule of the Financial Effect of Loan Modifications (Details) link:presentationLink link:calculationLink link:definitionLink 9954505 - Disclosure - PORTFOLIO LOANS - Schedule of Performance of Modified Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9954506 - Disclosure - PORTFOLIO LOANS - Schedule of Loans with Subsequent Defaults (Details) link:presentationLink link:calculationLink link:definitionLink 9954507 - Disclosure - PORTFOLIO LOANS - Schedule of Loans Evaluated Individually, Segregated by Loan Category and Class (Details) link:presentationLink link:calculationLink link:definitionLink 9954508 - Disclosure - PORTFOLIO LOANS - Schedule of Activity on the Allowance for Loan Losses (Details) link:presentationLink link:calculationLink link:definitionLink 9954509 - Disclosure - PORTFOLIO LOANS - Schedule of ACL and Amortized Cost of Portfolio Loans by Loan Category (Details) link:presentationLink link:calculationLink link:definitionLink 9954510 - Disclosure - LEASES - Schedule of Lease-Related Balances (Details) link:presentationLink link:calculationLink link:definitionLink 9954511 - Disclosure - LEASES - Schedule of Lease Costs and Other Lease Information (Details) link:presentationLink link:calculationLink link:definitionLink 9954512 - Disclosure - LEASES - Schedule of Future Undiscounted Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9954512 - Disclosure - LEASES - Schedule of Future Undiscounted Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9954513 - Disclosure - LEASES - Schedule of Revenue Recorded in Connection with Leases (Details) link:presentationLink link:calculationLink link:definitionLink 9954514 - Disclosure - LEASES - Schedule of Future Minimum Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9954515 - Disclosure - DEPOSITS - Schedule of Composition of Deposits (Details) link:presentationLink link:calculationLink link:definitionLink 9954516 - Disclosure - DEPOSITS - Schedule of Maturities of Time Deposits (Details) link:presentationLink link:calculationLink link:definitionLink 9954517 - Disclosure - BORROWINGS - Schedule of Securities Sold Under Agreements to Repurchase (Details) link:presentationLink link:calculationLink link:definitionLink 9954518 - Disclosure - BORROWINGS - Term Loan and Revolving Line of Credit (Details) link:presentationLink link:calculationLink link:definitionLink 9954519 - Disclosure - BORROWINGS - Schedule of Short-term Borrowings (Details) link:presentationLink link:calculationLink link:definitionLink 9954520 - Disclosure - BORROWINGS - Schedule of Long-term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 9954521 - Disclosure - BORROWINGS - Subordinated Notes (Details) link:presentationLink link:calculationLink link:definitionLink 9954522 - Disclosure - BORROWINGS - Schedule of Unamortized Debt Issuance Cost (Details) link:presentationLink link:calculationLink link:definitionLink 9954523 - Disclosure - REGULATORY CAPITAL - Schedule of Regulatory Capital Requirements Applicable to Busey and Busey Bank (Details) link:presentationLink link:calculationLink link:definitionLink 9954524 - Disclosure - REGULATORY CAPITAL - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954525 - Disclosure - TAX CREDIT AND OTHER INVESTMENTS IN UNCONSOLIDATED ENTITIES (Details) link:presentationLink link:calculationLink link:definitionLink 9954526 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Changes in the Company's Stock Option Awards (Details) link:presentationLink link:calculationLink link:definitionLink 9954527 - Disclosure - STOCK-BASED COMPENSATION - 2020 Equity Plan (Details) link:presentationLink link:calculationLink link:definitionLink 9954528 - Disclosure - STOCK-BASED COMPENSATION - RSU, PSU, and DSU Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954529 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Changes in the Company's RSU, PSU, and DSU Awards (Details) link:presentationLink link:calculationLink link:definitionLink 9954530 - Disclosure - STOCK-BASED COMPENSATION - Employee Stock Purchase Plan and Stock-based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954531 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954532 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Unamortized Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954533 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES (Details) link:presentationLink link:calculationLink link:definitionLink 9954534 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) link:presentationLink link:calculationLink link:definitionLink 9954535 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954536 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of the Interest-Rate Swaps Designated as Cash Flow Hedges (Details) link:presentationLink link:calculationLink link:definitionLink 9954537 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Reclassification of Unrealized Gains and Losses from OCI (Details) link:presentationLink link:calculationLink link:definitionLink 9954538 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Interest Income (Expense) Recorded on Swap Transactions (Details) link:presentationLink link:calculationLink link:definitionLink 9954539 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Net Gains (Losses) Recorded in AOCI (Details) link:presentationLink link:calculationLink link:definitionLink 9954540 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Interest Rate Swaps Not Designated as Hedges (Details) link:presentationLink link:calculationLink link:definitionLink 9954541 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Interest Rate Swaps Recorded in Noninterest Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9954542 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Risk Participation Agreement (Details) link:presentationLink link:calculationLink link:definitionLink 9954543 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Mortgage Banking Derivatives (Details) link:presentationLink link:calculationLink link:definitionLink 9954544 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Net Gains (Losses) Relating to Derivative Instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9954545 - 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 9954546 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Activity for Financial Assets Measured at Fair Value on a Recurring Basis (Details) link:presentationLink link:calculationLink link:definitionLink 9954547 - 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 9954548 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Quantitative Information About Level 3 Fair Value Measurements (Details) link:presentationLink link:calculationLink link:definitionLink 9954549 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Estimated Fair Values of Financial Instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9954550 - Disclosure - EARNINGS PER COMMON SHARE - Schedule of Computation of Earnings Per Common Share (Details) link:presentationLink link:calculationLink link:definitionLink 9954551 - Disclosure - EARNINGS PER COMMON SHARE - Schedule of Average Shares Excluded From Computation of Diluted Earnings Per Common Share (Details) link:presentationLink link:calculationLink link:definitionLink 9954552 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) link:presentationLink link:calculationLink link:definitionLink 9954553 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9954554 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION - Schedule of Information Relating to Operating Segments (Details) link:presentationLink link:calculationLink link:definitionLink