Basis of Presentation	6 Months Ended
Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation General In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments necessary to present fairly the consolidated balance sheets, statements of income, comprehensive income, changes in stockholders’ equity and cash flows of Nicolet Bankshares, Inc. (the “Company” or “Nicolet”) and its subsidiaries, for the periods presented, and all such adjustments are of a normal recurring nature. All material intercompany transactions and balances have been eliminated. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the entire year. These interim consolidated financial statements have been prepared according to the rules and regulations of the Securities and Exchange Commission and, therefore, certain information and footnote disclosures normally presented in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) have been omitted or abbreviated. These consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019. Critical Accounting Policies and Estimates Preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying disclosures. These estimates are based on management’s best knowledge of current events and actions the Company may undertake in the future. Estimates are used in accounting for, among other items, the allowance for credit losses, valuation of loans in acquisition transactions, useful lives for depreciation and amortization, fair value of financial instruments, other-than-temporary impairment calculations, valuation of deferred tax assets, uncertain income tax positions and contingencies. Estimates that are particularly susceptible to significant change for the Company include the determination of the allowance for credit losses, the determination and assessment of deferred tax assets and liabilities, and the valuation of loans acquired in acquisition transactions; therefore, these are critical accounting policies. Factors that may cause sensitivity to the aforementioned estimates include but are not limited to: external market factors such as market interest rates and employment rates, changes to operating policies and procedures, changes in applicable banking or tax regulations, and changes to deferred tax estimates. Actual results may ultimately differ from estimates, although management does not generally believe such differences would materially affect the consolidated financial statements in any individual reporting period presented. There have been no material changes or developments with respect to the assumptions or methodologies that the Company uses when applying what management believes are critical accounting policies and developing critical accounting estimates as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, except as disclosed in Updates to Significant Accounting Policies and Recent Accounting Developments Adopted below. Updates to Significant Accounting Policies Securities Available for Sale: Securities classified as AFS are those securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, regulatory capital considerations, and other similar factors. The Company evaluates securities AFS in unrealized loss positions on a quarterly basis to determine whether the decline in fair value below the amortized costs basis (impairment) is due to credit-related factors or noncredit-related factors. In making this evaluation, management considers the extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer, and the intent and ability of the Company to hold the security for a period of time sufficient to allow for any anticipated recovery in fair value. Any impairment that is not credit-related is recognized in other comprehensive income, net of related deferred income taxes. Credit-related impairment is recognized as an allowance for credit losses (“ACL”) on the balance sheet based on the amount by which the amortized cost basis exceeds the fair value, with a corresponding charge to net income. Both the ACL and the charge to net income may be reversed if conditions change. However, if the Company intends to sell an impaired AFS security or more likely than not will be required to sell such a security before recovering its amortized cost basis, the entire impairment amount must be recognized in net income with a corresponding adjustment to the security's amortized cost basis rather than through the establishment of an ACL. See Note 5 for additional disclosures on AFS securities. Loans – Originated: Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are carried at their amortized cost basis, which is the unpaid principal balance outstanding, net of deferred loan fees and costs and any direct principal charge-offs. The Company made an accounting policy election to exclude accrued interest from the amortized cost basis of loans and report such accrued interest as part of accrued interest receivable and other assets on the consolidated balance sheets. Interest income is accrued on the unpaid principal balance using the simple interest method. The accrual of interest income on loans is discontinued when, in the opinion of management, there is reasonable doubt as to the borrower’s ability to meet payment of interest or principal when due. Loans are generally placed on nonaccrual status when contractually past due 90 days or more as to interest or principal, though may be placed in such status earlier based on the circumstances. Loans past due 90 days or more may continue on accrual only when they are well secured and/or in process of collection or renewal. When interest accrual is discontinued, all previously accrued but uncollected interest is reversed against current period interest income. Except in very limited circumstances, cash collections on nonaccrual loans are credited to the loan receivable balance and no interest income is recognized on those loans until the principal balance is paid in full. Accrual of interest may be resumed when the customer is current on all principal and interest payments and has been paying on a timely basis for a sustained period of time. See Note 6 for additional information and disclosures on loans. Loans – Acquired: Loans purchased in acquisition transactions are acquired loans, and are recorded at their estimated fair value at the acquisition date. Prior to January 1, 2020, as described in further detail in the Company’s 2019 Annual Report on Form 10-K, the Company initially classified acquired loans as either purchased credit impaired (“PCI”) loans (i.e., loans that reflect credit deterioration since origination and it is probable at acquisition that the Company will be unable to collect all contractually required payments) or purchased non-impaired loans (i.e., “performing acquired loans”). The Company estimated the fair value of PCI loans based on the amount and timing of expected principal, interest and other cash flows for each loan. The excess of the loan’s contractual principal and interest payments over all cash flows expected to be collected at acquisition was considered an amount that should not be accreted. These credit discounts (“nonaccretable marks”) were included in the determination of the initial fair value for acquired loans; therefore, no allowance for credit losses was recorded at the acquisition date. Differences between the estimated fair values and expected cash flows of acquired loans at the acquisition date that were not credit-based (“accretable marks”) were subsequently accreted to interest income over the estimated life of the loans. Subsequent to the acquisition date for PCI loans, increases in cash flows over those expected at the acquisition date resulted in a move of the discount from nonaccretable to accretable, while decreases in expected cash flows after the acquisition date were recognized through the provision for credit losses. Subsequent to January 1, 2020, acquired loans that have evidence of more-than-insignificant deterioration in credit quality since origination are considered purchased credit deteriorated (“PCD”) loans. At acquisition, an estimate of expected credit losses is made for PCD loans. This initial allowance for credit losses is allocated to individual PCD loans and added to the purchase price or acquisition date fair value to establish the initial amortized cost basis of the PCD loans. Any difference between the unpaid principal balance of PCD loans and the amortized cost basis is considered to relate to noncredit factors, resulting in a discount or premium that is amortized to interest income. For acquired loans not deemed PCD loans at acquisition, the difference between the initial fair value mark and the unpaid principal balance are recognized in interest income over the estimated life of the loans. In addition, an initial allowance for expected credit losses is estimated and recorded as provision expense at the acquisition date. The subsequent measurement of expected credit losses for all acquired loans is the same as the subsequent measurement of expected credit losses for originated loans. See Note 6 for additional information and disclosures on loans. Allowance for Credit Losses - Loans: The ACL-Loans represents management’s estimate of expected credit losses in the Company’s loan portfolio at the balance sheet date. The Company estimates the ACL-Loans based on the amortized cost basis of the underlying loan and has made an accounting policy election to exclude accrued interest from the loan’s amortized cost basis and the related measurement of the ACL-Loans. Estimating the amount of the ACL-Loans is a function of a number of factors, including but not limited to changes in the loan portfolio, net charge-offs, trends in past due and nonaccrual loans, and the level of potential problem loans, all of which may be susceptible to significant change. Prior to January 1, 2020, as described in further detail in the Company’s 2019 Annual Report on Form 10-K, the Company used an incurred loss impairment model. This methodology assessed the overall appropriateness of the allowance for credit losses and included allocations for specifically identified impaired loans and loss factors for all remaining loans, with a component primarily based on historical loss rates and another component primarily based on other qualitative factors. Impaired loans were individually assessed and measured based on the present value of expected future cash flows discounted at the loan’s effective interest rate, the loan’s observable market price or the fair value of the collateral if the loan was collateral dependent. Loans that were determined not to be impaired were collectively evaluated for impairment, stratified by type and allocated loss ranges based on the Company’s actual historical loss ratios for each strata, and adjustments were also provided for certain environmental and other qualitative factors. Subsequent to January 1, 2020, the Company uses a current expected credit loss model (“CECL”). This methodology also considers historical loss rates and other qualitative adjustments, as well as a new forward-looking component that considers reasonable and supportable forecasts over the expected life of each loan. To develop the ACL-Loans estimate under the CECL model, the Company segments the loan portfolio into loan pools based on loan type and similar credit risk elements; performs an individual evaluation of PCD loans; calculates the historical loss rates for the segmented loan pools; applies the loss rates over the calculated life of the pooled loans; adjusts for forecasted macro-level economic conditions; and determines qualitative adjustments based on factors and conditions unique to Nicolet's portfolio. Recent Accounting Developments Adopted In August 2018, the FASB issued Accounting Standards Update (“ASU”) 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This ASU modifies the disclosure requirements for fair value measurements by removing, modifying or adding certain disclosures. The updated guidance was effective for annual reporting periods, including interim periods within those fiscal years, beginning after December 15, 2019. The Company adopted the updated guidance effective January 1, 2020, with no material impact on its consolidated financial statements as the new ASU only revises disclosure requirements. See Note 9 for fair value disclosures. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments intended to improve the financial reporting by requiring earlier recognition of credit losses on loans and certain other financial assets. Topic 326 replaces the incurred loss impairment model (which recognizes losses when a probable threshold is met) with a requirement to recognize lifetime expected credit losses immediately when a financial asset is originated or purchased. The measurement of lifetime expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts. The ASU was effective for SEC filers for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The Company adopted the new accounting standard on January 1, 2020, as required, and recorded a cumulative-effect adjustment of $6 million to retained earnings. See Updates to Significant Accounting Policies above for changes to accounting policies and see Notes 5 and 6 for additional disclosures related to this new accounting pronouncement. Reclassifications Certain amounts in the 2019 consolidated financial statements have been reclassified to conform to the 2020 presentation.

In the opinion of management, the accompanying unaudited consolidated financial statements contain all adjustments necessary to present fairly the consolidated balance sheets, statements of income, comprehensive income, changes in stockholders’ equity and cash flows of Nicolet Bankshares, Inc. (the “Company” or “Nicolet”) and its subsidiaries, for the periods presented, and all such adjustments are of a normal recurring nature. All material intercompany transactions and balances have been eliminated. The results of operations for the interim periods are not necessarily indicative of the results to be expected for the entire year.

These interim consolidated financial statements have been prepared according to the rules and regulations of the Securities and Exchange Commission and, therefore, certain information and footnote disclosures normally presented in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) have been omitted or abbreviated. These consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019.

Preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying disclosures. These estimates are based on management’s best knowledge of current events and actions the Company may undertake in the future. Estimates are used in accounting for, among other items, the allowance for credit losses, valuation of loans in acquisition transactions, useful lives for depreciation and amortization, fair value of financial instruments, other-than-temporary impairment calculations, valuation of deferred tax assets, uncertain income tax positions and contingencies. Estimates that are particularly susceptible to significant change for the Company include the determination of the allowance for credit losses, the determination and assessment of deferred tax assets and liabilities, and the valuation of loans acquired in acquisition transactions; therefore, these are critical accounting policies. Factors that may cause sensitivity to the aforementioned estimates include but are not limited to: external market factors such as market interest rates and employment rates, changes to operating policies and procedures, changes in applicable banking or tax regulations, and changes to deferred tax estimates. Actual results may ultimately differ from estimates, although management does not generally believe such differences would materially affect the consolidated financial statements in any individual reporting period presented.

There have been no material changes or developments with respect to the assumptions or methodologies that the Company uses when applying what management believes are critical accounting policies and developing critical accounting estimates as disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019, except as disclosed in Updates to Significant Accounting Policies and Recent Accounting Developments Adopted below.

Securities Available for Sale: Securities classified as AFS are those securities that the Company intends to hold for an indefinite period of time, but not necessarily to maturity. Any decision to sell a security classified as AFS would be based on various factors, including significant movements in interest rates, changes in the maturity mix of the Company’s assets and liabilities, liquidity needs, regulatory capital considerations, and other similar factors.

The Company evaluates securities AFS in unrealized loss positions on a quarterly basis to determine whether the decline in fair value below the amortized costs basis (impairment) is due to credit-related factors or noncredit-related factors. In making this evaluation, management considers the extent to which the fair value has been less than cost, the financial condition and near-term prospects of the issuer, and the intent and ability of the Company to hold the security for a period of time sufficient to allow for any anticipated recovery in fair value. Any impairment that is not credit-related is recognized in other comprehensive income, net of related deferred income taxes. Credit-related impairment is recognized as an allowance for credit losses (“ACL”) on the balance sheet based on the amount by which the amortized cost basis exceeds the fair value, with a corresponding charge to net income. Both the ACL and the charge to net income may be reversed if conditions change. However, if the Company intends to sell an impaired AFS security or more likely than not will be required to sell such a security before recovering its amortized cost basis, the entire impairment amount must be recognized in net income with a corresponding adjustment to the security's amortized cost basis rather than through the establishment of an ACL. See Note 5 for additional disclosures on AFS securities.

Loans – Originated: Loans that management has the intent and ability to hold for the foreseeable future or until maturity or payoff are carried at their amortized cost basis, which is the unpaid principal balance outstanding, net of deferred loan fees and costs and any direct principal charge-offs. The Company made an accounting policy election to exclude accrued interest from the amortized cost basis of loans and report such accrued interest as part of accrued interest receivable and other assets on the consolidated balance sheets.

Interest income is accrued on the unpaid principal balance using the simple interest method. The accrual of interest income on loans is discontinued when, in the opinion of management, there is reasonable doubt as to the borrower’s ability to meet payment of interest or principal when due. Loans are generally placed on nonaccrual status when contractually past due 90 days or more as to interest or principal, though may be placed in such status earlier based on the circumstances. Loans past due 90 days or more may continue on accrual only when they are well secured and/or in process of collection or renewal. When interest accrual is discontinued, all previously accrued but uncollected interest is reversed against current period interest income. Except in very limited circumstances, cash collections on nonaccrual loans are credited to the loan receivable balance and no interest income is recognized on those loans until the principal balance is paid in full. Accrual of interest may be resumed when the customer is current on all principal and interest payments and has been paying on a timely basis for a sustained period of time. See Note 6 for additional information and disclosures on loans.

Prior to January 1, 2020, as described in further detail in the Company’s 2019 Annual Report on Form 10-K, the Company initially classified acquired loans as either purchased credit impaired (“PCI”) loans (i.e., loans that reflect credit deterioration since origination and it is probable at acquisition that the Company will be unable to collect all contractually required payments) or purchased non-impaired loans (i.e., “performing acquired loans”). The Company estimated the fair value of PCI loans based on the amount and timing of expected principal, interest and other cash flows for each loan. The excess of the loan’s contractual principal and interest payments over all cash flows expected to be collected at acquisition was considered an amount that should not be accreted. These credit discounts (“nonaccretable marks”) were included in the determination of the initial fair value for acquired loans; therefore, no allowance for credit losses was recorded at the acquisition date. Differences between the estimated fair values and expected cash flows of acquired loans at the acquisition date that were not credit-based (“accretable marks”) were subsequently accreted to interest income over the estimated life of the loans. Subsequent to the acquisition date for PCI loans, increases in cash flows over those expected at the acquisition date resulted in a move of the discount from nonaccretable to accretable, while decreases in expected cash flows after the acquisition date were recognized through the provision for credit losses.

Subsequent to January 1, 2020, acquired loans that have evidence of more-than-insignificant deterioration in credit quality since origination are considered purchased credit deteriorated (“PCD”) loans. At acquisition, an estimate of expected credit losses is made for PCD loans. This initial allowance for credit losses is allocated to individual PCD loans and added to the purchase price or acquisition date fair value to establish the initial amortized cost basis of the PCD loans. Any difference between the unpaid principal balance of PCD loans and the amortized cost basis is considered to relate to noncredit factors, resulting in a discount or premium that is amortized to interest income. For acquired loans not deemed PCD loans at acquisition, the difference between the initial fair value mark and the unpaid principal balance are recognized in interest income over the estimated life of the loans. In addition, an initial allowance for expected credit losses is estimated and recorded as provision expense at the acquisition date. The subsequent measurement of expected credit losses for all acquired loans is the same as the subsequent measurement of expected credit losses for originated loans. See Note 6 for additional information and disclosures on loans.

Allowance for Credit Losses - Loans: The ACL-Loans represents management’s estimate of expected credit losses in the Company’s loan portfolio at the balance sheet date. The Company estimates the ACL-Loans based on the amortized cost basis of the underlying loan and has made an accounting policy election to exclude accrued interest from the loan’s amortized cost basis and the related measurement of the ACL-Loans. Estimating the amount of the ACL-Loans is a function of a number of factors, including but not limited to changes in the loan portfolio, net charge-offs, trends in past due and nonaccrual loans, and the level of potential problem loans, all of which may be susceptible to significant change.

Prior to January 1, 2020, as described in further detail in the Company’s 2019 Annual Report on Form 10-K, the Company used an incurred loss impairment model. This methodology assessed the overall appropriateness of the allowance for credit losses and included allocations for specifically identified impaired loans and loss factors for all remaining loans, with a component primarily based on historical loss rates and another component primarily based on other qualitative factors. Impaired loans were individually assessed and measured based on the present value of expected future cash flows discounted at the loan’s effective interest rate, the loan’s observable market price or the fair value of the collateral if the loan was collateral dependent. Loans that were determined not to be impaired were collectively evaluated for impairment, stratified by type and allocated loss ranges based on the Company’s actual historical loss ratios for each strata, and adjustments were also provided for certain environmental and other qualitative factors.

Subsequent to January 1, 2020, the Company uses a current expected credit loss model (“CECL”). This methodology also considers historical loss rates and other qualitative adjustments, as well as a new forward-looking component that considers reasonable and supportable forecasts over the expected life of each loan. To develop the ACL-Loans estimate under the CECL

model, the Company segments the loan portfolio into loan pools based on loan type and similar credit risk elements; performs an individual evaluation of PCD loans; calculates the historical loss rates for the segmented loan pools; applies the loss rates over the calculated life of the pooled loans; adjusts for forecasted macro-level economic conditions; and determines qualitative adjustments based on factors and conditions unique to Nicolet's portfolio.

In August 2018, the FASB issued Accounting Standards Update (“ASU”) 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. This ASU modifies the disclosure requirements for fair value measurements by removing, modifying or adding certain disclosures. The updated guidance was effective for annual reporting periods, including interim periods within those fiscal years, beginning after December 15, 2019. The Company adopted the updated guidance effective January 1, 2020, with no material impact on its consolidated financial statements as the new ASU only revises disclosure requirements. See Note 9 for fair value disclosures.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments intended to improve the financial reporting by requiring earlier recognition of credit losses on loans and certain other financial assets. Topic 326 replaces the incurred loss impairment model (which recognizes losses when a probable threshold is met) with a requirement to recognize lifetime expected credit losses immediately when a financial asset is originated or purchased. The measurement of lifetime expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts. The ASU was effective for SEC filers for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The Company adopted the new accounting standard on January 1, 2020, as required, and recorded a cumulative-effect adjustment of $6 million to retained earnings. See Updates to Significant Accounting Policies above for changes to accounting policies and see Notes 5 and 6 for additional disclosures related to this new accounting pronouncement.