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 STOCKHOLDERS' EQUITY (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952156 - Statement - CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 9952157 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) link:presentationLink link:calculationLink link:definitionLink 9952158 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES link:presentationLink link:calculationLink link:definitionLink 9952159 - Disclosure - MERGERS AND ACQUISITIONS link:presentationLink link:calculationLink link:definitionLink 9952160 - Disclosure - DEBT SECURITIES link:presentationLink link:calculationLink link:definitionLink 9952161 - Disclosure - PORTFOLIO LOANS link:presentationLink link:calculationLink link:definitionLink 9952162 - Disclosure - LEASES link:presentationLink link:calculationLink link:definitionLink 9952163 - Disclosure - DEPOSITS link:presentationLink link:calculationLink link:definitionLink 9952164 - Disclosure - BORROWINGS link:presentationLink link:calculationLink link:definitionLink 9952165 - Disclosure - REGULATORY CAPITAL link:presentationLink link:calculationLink link:definitionLink 9952166 - Disclosure - TAX CREDIT INVESTMENTS AND OTHER INVESTMENTS IN UNCONSOLIDATED ENTITIES link:presentationLink link:calculationLink link:definitionLink 9952167 - Disclosure - STOCK-BASED COMPENSATION link:presentationLink link:calculationLink link:definitionLink 9952168 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES link:presentationLink link:calculationLink link:definitionLink 9952169 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS link:presentationLink link:calculationLink link:definitionLink 9952170 - Disclosure - FAIR VALUE MEASUREMENTS link:presentationLink link:calculationLink link:definitionLink 9952171 - Disclosure - EARNINGS PER COMMON SHARE link:presentationLink link:calculationLink link:definitionLink 9952172 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) link:presentationLink link:calculationLink link:definitionLink 9952173 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION link:presentationLink link:calculationLink link:definitionLink 9955511 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES (Policies) link:presentationLink link:calculationLink link:definitionLink 9955512 - Disclosure - MERGERS AND ACQUISITIONS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955513 - Disclosure - DEBT SECURITIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9955514 - Disclosure - PORTFOLIO LOANS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955515 - Disclosure - LEASES (Tables) link:presentationLink link:calculationLink link:definitionLink 9955516 - Disclosure - DEPOSITS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955517 - Disclosure - BORROWINGS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955518 - Disclosure - REGULATORY CAPITAL (Tables) link:presentationLink link:calculationLink link:definitionLink 9955519 - Disclosure - TAX CREDIT INVESTMENTS AND OTHER INVESTMENTS IN UNCONSOLIDATED ENTITIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9955520 - Disclosure - STOCK-BASED COMPENSATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9955521 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES (Tables) link:presentationLink link:calculationLink link:definitionLink 9955522 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955523 - Disclosure - FAIR VALUE MEASUREMENTS (Tables) link:presentationLink link:calculationLink link:definitionLink 9955524 - Disclosure - EARNINGS PER COMMON SHARE (Tables) link:presentationLink link:calculationLink link:definitionLink 9955525 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Tables) link:presentationLink link:calculationLink link:definitionLink 9955526 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION (Tables) link:presentationLink link:calculationLink link:definitionLink 9955527 - Disclosure - SIGNIFICANT ACCOUNTING POLICIES (Details) link:presentationLink link:calculationLink link:definitionLink 9955528 - Disclosure - MERGERS AND ACQUISITIONS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955529 - 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 9955530 - Disclosure - MERGERS AND ACQUISITIONS - Schedule of Reconciliation Between the Purchase Price and the Fair Value (Details) link:presentationLink link:calculationLink link:definitionLink 9955531 - Disclosure - MERGERS AND ACQUISITIONS - Schedule of Pro Forma Information (Details) link:presentationLink link:calculationLink link:definitionLink 9955532 - Disclosure - MERGERS AND ACQUISITIONS - Schedule of Pre-tax acquisition expenses (Details) link:presentationLink link:calculationLink link:definitionLink 9955533 - Disclosure - MERGERS AND ACQUISITIONS - Schedule of Pre-tax costs to consummate the merger (Details) link:presentationLink link:calculationLink link:definitionLink 9955534 - 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 9955535 - Disclosure - DEBT SECURITIES - Schedule of Maturity of Debt Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9955536 - Disclosure - DEBT SECURITIES - Schedule of Realized Gains and Losses on Debt Securities (Details) link:presentationLink link:calculationLink link:definitionLink 9955537 - Disclosure - DEBT SECURITIES - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955538 - Disclosure - DEBT SECURITIES - Schedule of Debt Securities in an Unrealized or Unrecognized Loss Position (Details) link:presentationLink link:calculationLink link:definitionLink 9955539 - Disclosure - DEBT SECURITIES - Schedule of Additional Information on Debt Securities In Unrealized or Unrecognized Loss Position (Details) link:presentationLink link:calculationLink link:definitionLink 9955540 - Disclosure - PORTFOLIO LOANS - Schedule of Distribution of Portfolio Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9955541 - Disclosure - PORTFOLIO LOANS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955542 - Disclosure - PORTFOLIO LOANS - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) link:presentationLink link:calculationLink link:definitionLink 9955543 - Disclosure - PORTFOLIO LOANS - Schedule of Risk Grades Segregated by Category and Class of Portfolio Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9955544 - Disclosure - PORTFOLIO LOANS - Schedule of Risk Grades of Portfolio Loans, Further Sorted by Origination (Details) link:presentationLink link:calculationLink link:definitionLink 9955545 - Disclosure - PORTFOLIO LOANS - Schedule of Past Due and Non-accrual Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9955546 - Disclosure - PORTFOLIO LOANS - Schedule of Loan Modifications for Borrowers Experiencing Financial Difficulty (Details) link:presentationLink link:calculationLink link:definitionLink 9955547 - Disclosure - PORTFOLIO LOANS - Schedule of the Financial Effect of Loan Modifications (Details) link:presentationLink link:calculationLink link:definitionLink 9955548 - Disclosure - PORTFOLIO LOANS - Schedule of Performance of Modified Loans (Details) link:presentationLink link:calculationLink link:definitionLink 9955549 - Disclosure - PORTFOLIO LOANS - Schedule of Activity on the Allowance for Loan Losses (Details) link:presentationLink link:calculationLink link:definitionLink 9955550 - Disclosure - LEASES - Schedule of Lease-Related Balances (Details) link:presentationLink link:calculationLink link:definitionLink 9955551 - Disclosure - LEASES - Schedule of Lease Costs and Other Lease Information (Details) link:presentationLink link:calculationLink link:definitionLink 9955552 - Disclosure - LEASES - Schedule of Future Undiscounted Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9955552 - Disclosure - LEASES - Schedule of Future Undiscounted Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9955553 - Disclosure - LEASES - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955554 - Disclosure - LEASES - Schedule of Revenue Recorded in Connection with Leases (Details) link:presentationLink link:calculationLink link:definitionLink 9955555 - Disclosure - LEASES - Schedule of Future Minimum Lease Payments (Details) link:presentationLink link:calculationLink link:definitionLink 9955556 - Disclosure - DEPOSITS - Schedule of Composition of Deposits (Details) link:presentationLink link:calculationLink link:definitionLink 9955557 - Disclosure - DEPOSITS - Schedule of Maturities of Time Deposits (Details) link:presentationLink link:calculationLink link:definitionLink 9955558 - Disclosure - BORROWINGS - Schedule of Securities Sold Under Agreements to Repurchase (Details) link:presentationLink link:calculationLink link:definitionLink 9955559 - Disclosure - BORROWINGS - Revolving Line of Credit Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955560 - Disclosure - BORROWINGS - Schedule of Short-term Borrowings (Details) link:presentationLink link:calculationLink link:definitionLink 9955561 - Disclosure - BORROWINGS - Schedule of Long-term Debt (Details) link:presentationLink link:calculationLink link:definitionLink 9955562 - Disclosure - BORROWINGS - Subordinated Notes Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955563 - Disclosure - BORROWINGS - Schedule of Unamortized Debt Issuance Cost (Details) link:presentationLink link:calculationLink link:definitionLink 9955564 - Disclosure - REGULATORY CAPITAL - Schedule of Regulatory Capital Requirements Applicable to Busey and Busey Bank (Details) link:presentationLink link:calculationLink link:definitionLink 9955565 - Disclosure - REGULATORY CAPITAL - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955566 - Disclosure - TAX CREDIT INVESTMENTS AND OTHER INVESTMENTS IN UNCONSOLIDATED ENTITIES (Details) link:presentationLink link:calculationLink link:definitionLink 9955567 - Disclosure - STOCK-BASED COMPENSATION - CrossFirst Acquisition (Details) link:presentationLink link:calculationLink link:definitionLink 9955568 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Changes in the Company's Stock Option Awards (Details) link:presentationLink link:calculationLink link:definitionLink 9955569 - Disclosure - STOCK-BASED COMPENSATION - Stock Settled Appreciation Rights Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955570 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Stock Appreciation Rights Activity (Details) link:presentationLink link:calculationLink link:definitionLink 9955571 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Stock Appreciation Rights Valuation Assumptions (Details) link:presentationLink link:calculationLink link:definitionLink 9955572 - Disclosure - STOCK-BASED COMPENSATION - 2020 Equity Plan (Details) link:presentationLink link:calculationLink link:definitionLink 9955573 - Disclosure - STOCK-BASED COMPENSATION - RSU, PSU, and DSU Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955574 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Changes in the Company's RSU, PSU, and DSU Awards (Details) link:presentationLink link:calculationLink link:definitionLink 9955575 - Disclosure - STOCK-BASED COMPENSATION - Employee Stock Purchase Plan and Stock-based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9955576 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9955577 - Disclosure - STOCK-BASED COMPENSATION - Schedule of Unamortized Stock-Based Compensation Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9955578 - Disclosure - OUTSTANDING COMMITMENTS AND CONTINGENT LIABILITIES (Details) link:presentationLink link:calculationLink link:definitionLink 9955579 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Financial Instruments Owned and Pledged as Collateral (Details) link:presentationLink link:calculationLink link:definitionLink 9955580 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955581 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of the Interest-Rate Swaps Designated as Cash Flow Hedges (Details) link:presentationLink link:calculationLink link:definitionLink 9955582 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Reclassification of Unrealized Gains and Losses from OCI (Details) link:presentationLink link:calculationLink link:definitionLink 9955583 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Interest Income (Expense) Recorded on Swap Transactions (Details) link:presentationLink link:calculationLink link:definitionLink 9955584 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Net Gains (Losses) Recorded in AOCI (Details) link:presentationLink link:calculationLink link:definitionLink 9955585 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Interest Rate Swaps Not Designated as Hedges (Details) link:presentationLink link:calculationLink link:definitionLink 9955586 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Interest Rate Swaps Recorded in Noninterest Expense (Details) link:presentationLink link:calculationLink link:definitionLink 9955587 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Risk Participation Agreement (Details) link:presentationLink link:calculationLink link:definitionLink 9955588 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Mortgage Banking Derivatives (Details) link:presentationLink link:calculationLink link:definitionLink 9955589 - Disclosure - DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Net Gains (Losses) Relating to Derivative Instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9955590 - 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 9955591 - 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 9955592 - 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 9955593 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Quantitative Information About Level 3 Fair Value Measurements (Details) link:presentationLink link:calculationLink link:definitionLink 9955594 - Disclosure - FAIR VALUE MEASUREMENTS - Schedule of Estimated Fair Values of Financial Instruments (Details) link:presentationLink link:calculationLink link:definitionLink 9955595 - Disclosure - EARNINGS PER COMMON SHARE - Schedule of Computation of Earnings Per Common Share (Details) link:presentationLink link:calculationLink link:definitionLink 9955596 - 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 9955597 - Disclosure - EARNINGS PER COMMON SHARE - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955598 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) link:presentationLink link:calculationLink link:definitionLink 9955599 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 9955600 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION - Schedule of Goodwill and Total Assets of Segments (Details) link:presentationLink link:calculationLink link:definitionLink 9955601 - Disclosure - OPERATING SEGMENTS AND RELATED INFORMATION - Schedule of Financial Results by Operating Segment (Details) link:presentationLink link:calculationLink link:definitionLink