Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2020
Significant Accounting Policies
Impacts of COVID-19	Impacts of COVID-19 First Busey is positioned to execute its mission as an essential community resource during these challenging times. The coronavirus disease 2019 (“COVID-19”) is not only impacting health and safety around the world, it is causing significant economic disruption for both individuals and businesses, making the Company’s promise of support even more important to customers. In the face of the challenges and risks posed by COVID-19, the Company remains resolute in its focus on protecting the strength and flexibility of its balance sheet. The progression of the COVID-19 pandemic in the United States began to negatively impact the Company’s results of operations during the quarter ended March 31, 2020. Going forward, COVID-19 can be expected to have a complex and significant adverse impact on the economy, the banking industry and First Busey in future fiscal periods, all subject to a high degree of uncertainty as it relates to both timing and severity. Primary areas of impact in the future for First Busey may include margin compression, increased provision expense, a deterioration in asset quality and decreased wealth management fees and fees for customer services.
Subsequent Events	Subsequent Events The Company has evaluated subsequent events for potential recognition and/or disclosure through the date the unaudited consolidated financial statements included in this Quarterly Report on Form 10-Q were issued. There were no significant subsequent events for the quarter ended March 31, 2020 through the issuance date of these unaudited consolidated financial statements that warranted adjustment to or disclosure in the unaudited consolidated financial statements.
Use of Estimates	Use of Estimates In preparing the accompanying unaudited consolidated financial statements in conformity with GAAP, the Company’s management is required to make estimates and assumptions that affect the amounts reported in the financial statements and the disclosures provided. Actual results could differ from those estimates. Material estimates which are particularly susceptible to significant change in the near term relate to the fair value of investment securities, fair value of assets acquired and liabilities assumed in business combinations, goodwill, income taxes and the determination of the allowance.
Impact of recently adopted accounting standards	Impact of recently adopted accounting standards On January 1, 2020, First Busey adopted Accounting Standards Update (“ASU”) 2016-13 Financial Instruments – Credit Losses (“Topic 326”): Measurement of Credit Losses on Financial Instruments, as amended, which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss (“CECL”) methodology. The measurement of expected credit losses under the CECL methodology is applicable to financial assets measured at amortized cost, including loan receivables and held-to-maturity debt securities. It also applies to off-balance-sheet credit exposures not accounted for as insurance (loan commitments, standby letters of credit, financial guarantees, and other similar instruments) and net investments in leases recognized by a lessor in accordance with Topic 842 on leases. In addition, Accounting Standards Codification (“ASC”) 326 made changes to the accounting for available-for-sale debt securities. One such change is to require credit losses to be presented as an allowance rather than as a write-down on available-for-sale debt securities management does not intend to sell or believes that it is more likely than not they will be required to sell. First Busey adopted ASC 326 using the modified retrospective method for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP which includes a change in terminology from Allowance/Provision for Loan Losses to Allowance/Provision for Credit Losses. First Busey recorded a net decrease to retained earnings of $15.9 million as of January 1, 2020 for the cumulative effect of adopting ASC 326. This transition adjustment included $12.0 million in allowance for credit losses on loans and $3.9 million in reserve for off-balance-sheet credit exposures. First Busey adopted ASC 326 using the prospective transition approach for financial assets purchased with credit deterioration (“PCD”) that were previously classified as purchased credit impaired (“PCI”) and accounted for under ASC 310-30. In accordance with the standard, management did not reassess whether PCI assets met the criteria of PCD assets as of the date of adoption. In accordance with ASC 326, the amortized cost basis of PCD assets were adjusted to reflect an allowance for credit losses for any remaining credit discount. Subsequent changes in expected cash flows will be adjusted through the allowance for credit losses. The noncredit discount will be accreted into interest income at the effective interest rate as of January 1, 2020.

Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2020

First Busey is positioned to execute its mission as an essential community resource during these challenging times. The coronavirus disease 2019 (“COVID-19”) is not only impacting health and safety around the world, it is causing significant economic disruption for both individuals and businesses, making the Company’s promise of support even more important to customers. In the face of the challenges and risks posed by COVID-19, the Company remains resolute in its focus on protecting the strength and flexibility of its balance sheet. The progression of the COVID-19 pandemic in the United States began to negatively impact the Company’s results of operations during the quarter ended March 31, 2020. Going forward, COVID-19 can be expected to have a complex and significant adverse impact on the economy, the banking industry and First Busey in future fiscal periods, all subject to a high degree of uncertainty as it relates to both timing and severity. Primary areas of impact in the future for First Busey may include margin compression, increased provision expense, a deterioration in asset quality and decreased wealth management fees and fees for customer services.

Subsequent Events

The Company has evaluated subsequent events for potential recognition and/or disclosure through the date the unaudited consolidated financial statements included in this Quarterly Report on Form 10-Q were issued. There were no significant subsequent events for the quarter ended March 31, 2020 through the issuance date of these unaudited consolidated financial statements that warranted adjustment to or disclosure in the unaudited consolidated financial statements.

Use of Estimates

In preparing the accompanying unaudited consolidated financial statements in conformity with GAAP, the Company’s management is required to make estimates and assumptions that affect the amounts reported in the financial statements and the disclosures provided. Actual results could differ from those estimates. Material estimates which are particularly susceptible to significant change in the near term relate to the fair value of investment securities, fair value of assets acquired and liabilities assumed in business combinations, goodwill, income taxes and the determination of the allowance.

Impact of recently adopted accounting standards

On January 1, 2020, First Busey adopted Accounting Standards Update (“ASU”) 2016-13 Financial Instruments – Credit Losses (“Topic 326”): Measurement of Credit Losses on Financial Instruments, as amended, which replaces the incurred loss methodology with an expected loss methodology that is referred to as the current expected credit loss (“CECL”) methodology. The measurement of expected credit losses under the CECL methodology is applicable to financial assets measured at amortized cost, including loan receivables and held-to-maturity debt securities. It also applies to off-balance-sheet credit exposures not accounted for as insurance (loan commitments, standby letters of credit, financial guarantees, and other similar instruments) and net investments in leases recognized by a lessor in accordance with Topic 842 on leases. In addition, Accounting Standards Codification (“ASC”) 326 made changes to the accounting for available-for-sale debt securities. One such change is to require credit losses to be presented as an allowance rather than as a write-down on available-for-sale debt securities management does not intend to sell or believes that it is more likely than not they will be required to sell.

First Busey adopted ASC 326 using the modified retrospective method for all financial assets measured at amortized cost and off-balance-sheet credit exposures. Results for reporting periods beginning after January 1, 2020 are presented under ASC 326 while prior period amounts continue to be reported in accordance with previously applicable GAAP which includes a change in terminology from Allowance/Provision for Loan Losses to Allowance/Provision for Credit Losses. First Busey recorded a net decrease to retained earnings of $15.9 million as of January 1, 2020 for the cumulative effect of adopting ASC 326. This transition adjustment included $12.0 million in allowance for credit losses on loans and $3.9 million in reserve for off-balance-sheet credit exposures.

First Busey adopted ASC 326 using the prospective transition approach for financial assets purchased with credit deterioration (“PCD”) that were previously classified as purchased credit impaired (“PCI”) and accounted for under ASC 310-30. In accordance with the standard, management did not reassess whether PCI assets met the criteria of PCD assets as of the date of adoption. In accordance with ASC 326, the amortized cost basis of PCD assets were adjusted to reflect an allowance for credit losses for any remaining credit discount. Subsequent changes in expected cash flows will be adjusted through the allowance for credit losses. The noncredit discount will be accreted into interest income at the effective interest rate as of January 1, 2020.