Nicolet Bankshares (NIC) 10-K 26 Feb 21 2020 FY Annual report Financial data

Cover

Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Feb. 24, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-37700
Entity Registrant Name	NICOLET BANKSHARES, INC
Entity Incorporation, State or Country Code	WI
Entity Tax Identification Number	47-0871001
Entity Address, Address Line One	111 North Washington Street
Entity Address, City or Town	Green Bay
Entity Address, State or Province	WI
Entity Address, Postal Zip Code	54301
City Area Code	920
Local Phone Number	430-1400
Title of 12(b) Security	Common Stock, par value $0.01 per share
Trading Symbol	NCBS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 509
Entity Common Stock, Shares Outstanding		9,979,672
Documents Incorporated by Reference	Part III of Form 10-K – Portions of the Proxy Statement for the 2021 Annual Meeting of Shareholders.
Entity Central Index Key	0001174850
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)		Dec. 31, 2020	Dec. 31, 2019
Assets
Cash and due from banks		$ 88,460,000	$ 75,433,000
Interest-earning deposits		714,399,000	106,626,000
Federal funds sold		0	0
Cash and cash equivalents	[1]	802,859,000	182,059,000
Certificates of deposit in other banks		29,521,000	19,305,000
Securities available for sale (“AFS”), at fair value		539,337,000	449,302,000
Other investments		27,619,000	24,072,000
Loans held for sale		21,450,000	2,706,000
Loans		2,789,101,000	2,573,751,000
Allowance for credit losses - loans (“ACL-Loans”)		(32,173,000)	(13,972,000)
Loans, net		2,756,928,000	2,559,779,000
Premises and equipment, net		59,944,000	56,469,000
Bank owned life insurance (“BOLI”)		83,262,000	78,140,000
Goodwill and other intangibles, net		175,353,000	165,967,000
Accrued interest receivable and other assets		55,516,000	39,461,000
Total assets		4,551,789,000	3,577,260,000
Liabilities:
Noninterest-bearing demand deposits		1,212,787,000	819,055,000
Interest-bearing deposits		2,697,612,000	2,135,398,000
Total deposits		3,910,399,000	2,954,453,000
Short-term borrowings		0	0
Long-term borrowings		53,869,000	67,629,000
Accrued interest payable and other liabilities		48,332,000	38,188,000
Total liabilities		4,012,600,000	3,060,270,000
Stockholders’ Equity:
Common stock		100,000	106,000
Additional paid-in capital		273,390,000	312,733,000
Retained earnings		252,952,000	199,005,000
Accumulated other comprehensive income (loss)		12,747,000	4,418,000
Total Nicolet Bankshares, Inc. stockholders’ equity		539,189,000	516,262,000
Noncontrolling interest		0	728,000
Total stockholders’ equity and noncontrolling interest		539,189,000	516,990,000
Total liabilities, noncontrolling interest and stockholders’ equity		$ 4,551,789,000	$ 3,577,260,000
Preferred shares authorized (no par value) (in shares)		10,000,000	10,000,000
Preferred shares issued and outstanding (in shares)		0	0
Common shares authorized (par value $0.01 per share) (in shares)		30,000,000	30,000,000
Common shares outstanding (in shares)		10,011,342	10,587,738
Common shares issued (in shares)		10,030,267	10,610,259
[1]	Cash and cash equivalents at December 31, 2020 include restricted cash of $1.9 million pledged as collateral on interest rate swaps and no reserve balance was required with the Federal Reserve. At December 31, 2019 cash and cash equivalents included restricted cash of $1.3 million pledged as collateral on interest rate swaps and $6.0 million for the reserve balance required with the Federal Reserve, while at December 31, 2018, cash and cash equivalents included $6.3 million for the reserve balance required with the Federal Reserve and no cash was pledged as collateral on interest rate swaps.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Interest income:
Loans, including loan fees	$ 136,372	$ 125,524	$ 113,953
Investment securities:
Taxable	8,118	7,584	6,068
Tax-exempt	2,101	2,075	2,296
Other interest income	2,611	3,405	3,220
Total interest income	149,202	138,588	125,537
Interest expense:
Deposits	16,641	18,965	15,420
Short-term borrowings	66	5	9
Long-term borrowings	3,157	3,540	3,460
Total interest expense	19,864	22,510	18,889
Net interest income	129,338	116,078	106,648
Provision for credit losses	10,300	1,200	1,600
Net interest income after provision for credit losses	119,038	114,878	105,048
Noninterest income:
Mortgage income, net	29,807	11,878	6,344
BOLI income	2,710	2,369	2,418
Asset gains (losses), net	(1,805)	7,897	1,169
Other income	4,492	5,559	5,528
Total noninterest income	62,626	53,367	39,509
Noninterest expense:
Personnel	57,121	54,437	49,476
Occupancy, equipment and office	16,718	14,788	14,574
Business development and marketing	5,396	5,685	5,324
Data processing	10,694	9,950	9,514
Intangibles amortization	3,567	3,872	4,389
Other expense	7,223	8,067	6,481
Total noninterest expense	100,719	96,799	89,758
Income before income tax expense	80,945	71,446	54,799
Income tax expense	20,476	16,458	13,446
Net income	60,469	54,988	41,353
Less: Net income attributable to noncontrolling interest	347	347	317
Net income attributable to Nicolet Bankshares, Inc.	$ 60,122	$ 54,641	$ 41,036
Earnings per common share:
Basic (in dollars per share)	$ 5.82	$ 5.71	$ 4.26
Diluted (in dollars per share)	$ 5.70	$ 5.52	$ 4.12
Weighted average common shares outstanding:
Basic (in shares)	10,337,138	9,561,978	9,640,258
Diluted (in shares)	10,541,251	9,900,319	9,956,353
Trust services fee income
Noninterest income:
Fees and commissions	$ 6,463	$ 6,227	$ 6,498
Brokerage fee income
Noninterest income:
Fees and commissions	9,753	8,115	7,042
Service charges on deposit accounts
Noninterest income:
Fees and commissions	4,208	4,824	4,845
Card interchange income
Noninterest income:
Fees and commissions	$ 6,998	$ 6,498	$ 5,665

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 60,469	$ 54,988	$ 41,353
Unrealized gains (losses) on securities AFS:
Net unrealized holding gains (losses)	11,803	13,758	(3,715)
Net (gains) losses included in income	(395)	22	212
Income tax (expense) benefit	(3,079)	(3,722)	946
Total other comprehensive income (loss), net of tax	8,329	10,058	(2,557)
Comprehensive income	$ 68,798	$ 65,046	$ 38,796

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-In Capital	Retained Earnings	Retained EarningsCumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss)Cumulative Effect, Period of Adoption, Adjustment	Non- controlling Interest
Beginning balance at Dec. 31, 2017	$ 364,879	$ 0	$ 98	$ 263,835	$ 102,391	$ 937	$ (2,146)	$ (937)	$ 701
Comprehensive income:
Net income	41,353				41,036				317
Other comprehensive income (loss)	(2,557)						(2,557)
Stock-based compensation expense	4,901			4,901
Exercise of stock options, net	1,518		1	1,517
Issuance of common stock	282			282
Purchase and retirement of common stock	(22,749)		(4)	(22,745)
Distribution to noncontrolling interest	(275)								(275)
Ending balance at Dec. 31, 2018	387,352		95	247,790	144,364		(5,640)		743
Comprehensive income:
Net income	54,988				54,641				347
Other comprehensive income (loss)	10,058						10,058
Stock-based compensation expense	5,038			5,038
Exercise of stock options, net	8,150		3	8,147
Issuance of common stock in acquisitions, net of capitalized issuance costs	79,634		12	79,622
Issuance of common stock	592			592
Purchase and retirement of common stock	(28,460)		(4)	(28,456)
Distribution to noncontrolling interest	$ (362)								(362)
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Ending balance at Dec. 31, 2019	$ 516,990	$ (6,175)	106	312,733	199,005	$ (6,175)	4,418	$ 0	728
Comprehensive income:
Net income	60,469				60,122				347
Other comprehensive income (loss)	8,329						8,329
Stock-based compensation expense	5,700			5,700
Exercise of stock options, net	1,474			1,474
Issuance of common stock	581			581
Purchase and retirement of common stock	(42,088)		(6)	(42,082)
Purchase of noncontrolling interest	(5,876)			(5,016)					(860)
Distribution to noncontrolling interest	(215)								(215)
Ending balance at Dec. 31, 2020	$ 539,189		$ 100	$ 273,390	$ 252,952		$ 12,747		$ 0

Consolidated Statements of Ch_2

Consolidated Statements of Changes in Stockholders' Equity (Parentheticals) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Statement of Stockholders' Equity [Abstract]
Capitalized issuance costs	$ 163

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Cash Flows From Operating Activities:
Net income		$ 60,469		$ 54,988		$ 41,353
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion		10,685		7,311		6,282
Provision for credit losses		10,300		1,200		1,600
Provision for deferred taxes		3,127		(2,652)		(1,521)
Increase in cash surrender value of life insurance		(2,199)		(1,967)		(1,857)
Stock-based compensation expense		5,700		5,038		4,901
Assets (gains) losses, net		1,805		(7,897)		(1,169)
Gain on sale of loans held for sale, net		(29,966)		(11,244)		(5,499)
Proceeds from sale of loans held for sale		854,608		425,530		241,739
Origination of loans held for sale		(848,337)		(418,229)		(234,416)
Net change in accrued interest receivable and other assets		6,991		(2,951)		(666)
Net change in accrued interest payable and other liabilities		5,716		9,010		242
Net cash provided by (used in) operating activities		78,899		58,137		50,989
Cash Flows From Investing Activities:
Net (increase) decrease in certificates of deposit in other banks		9,167		(1,924)		753
Purchases of securities AFS		(170,518)		(95,627)		(76,564)
Proceeds from sales of securities AFS		19,045		23,405		5,280
Proceeds from calls and maturities of securities AFS		94,818		53,933		66,706
Net (increase) decrease in loans		(125,020)		(57,156)		(71,629)
Purchases of other investments		(4,360)		(2,669)		(1,550)
Proceeds from sales of other investments		0		17,144		807
Net increase in premises and equipment		(10,791)		(4,392)		(4,260)
Proceeds from sales of other real estate and other assets		343		457		2,824
Purchase of BOLI		0		(5,000)		0
Proceeds from redemption of BOLI		440		1,348		561
Net cash paid in business combination		(21,820)
Net cash received in business combination				7,331		0
Net cash provided by (used in) investing activities		(208,696)		(63,150)		(77,072)
Cash Flows From Financing Activities:
Net increase (decrease) in deposits		815,094		49,259		143,153
Net increase (decrease) in short-term borrowings		0		(4,233)		0
Proceeds from long-term borrowings		367,842		0		0
Repayments of long-term borrowings		(384,091)		(87,237)		(1,253)
Distribution to noncontrolling interest		(215)		(362)		(275)
Purchase of noncontrolling interest		(8,000)		0		0
Capitalized issuance costs, net		0		(163)		0
Purchase and retirement of common stock		(42,088)		(28,460)		(22,749)
Proceeds from issuance of common stock, net		2,055		8,742		1,800
Net cash provided by (used in) financing activities		750,597		(62,454)		120,676
Net increase (decrease) in cash and cash equivalents		620,800		(67,467)		94,593
Cash and cash equivalents:
Beginning cash and cash equivalents		182,059	[1]	249,526	[1]	154,933
Ending cash and cash equivalents	[1]	802,859		182,059		249,526
Supplemental Disclosures of Cash Flow Information:
Cash paid for interest		23,485		22,334		18,537
Cash paid for taxes		21,969		16,140		10,821
Transfer of loans and bank premises to other real estate owned		2,608		1,025		607
Capitalized mortgage servicing rights		5,256		2,876		1,203
Acquisitions:
Fair value of assets acquired		160,000		412,000		0
Fair value of liabilities assumed		146,000		377,000		0
Net assets acquired		14,000		35,000		0
Common stock issued in acquisitions		$ 0		$ 79,797		$ 0
[1]	Cash and cash equivalents at December 31, 2020 include restricted cash of $1.9 million pledged as collateral on interest rate swaps and no reserve balance was required with the Federal Reserve. At December 31, 2019 cash and cash equivalents included restricted cash of $1.3 million pledged as collateral on interest rate swaps and $6.0 million for the reserve balance required with the Federal Reserve, while at December 31, 2018, cash and cash equivalents included $6.3 million for the reserve balance required with the Federal Reserve and no cash was pledged as collateral on interest rate swaps.

Consolidated Statements of Ca_2

Consolidated Statements of Cash Flows (Parenthetical) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Cash Flows [Abstract]
Restricted cash pledged as collateral	$ 1,900,000	$ 1,300,000	$ 0
Restricted cash	$ 0	$ 6,000,000	$ 6,300,000

NATURE OF BUSINESS AND SIGNIFIC

NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES	NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES Nature of Banking Activities and Subsidiaries : Nicolet Bankshares, Inc. (the “Company” or “Nicolet”) was incorporated on April 5, 2000, to serve as the holding company and sole shareholder of Nicolet National Bank (the “Bank”). The Bank opened for business on November 1, 2000. Since its opening in late 2000, Nicolet has supplemented its organic growth with branch purchase and acquisition transactions. See Note 2 for additional information on the Company’s recent acquisitions. At December 31, 2020, the Company had two wholly owned subsidiaries, the Bank and Nicolet Advisory Services, LLC (“Nicolet Advisory”). At December 31, 2020, the Bank wholly owns an investment subsidiary based in Nevada, a subsidiary in Green Bay that provides a web-based investment management platform for financial advisor trades and related activity, and an entity that owns the building in which Nicolet is headquartered, Nicolet Joint Ventures, LLC (the “JV”). The JV was owned 50% by a real estate development and investment firm (the “Firm”) through the JV until late 2020 when the Bank became the 100% owner and sole managing member of the JV. The Firm is considered a related party, as one of its principals is a Board member and shareholder of the Company. See Note 14 for additional related party disclosures, including details of the 50% interest purchased from the Firm. Nicolet Advisory is a registered investment advisor subsidiary that provides brokerage and investment advisory services to customers. In late 2020, to improve process efficiencies and organizational structure, the Company dissolved its wholly owned subsidiary, Brookfield Investment Partners, LLC, which provided limited investment services (transactional and strategy) to a few smaller banks, and Nicolet Advisory assumed those additional investment services contracts. Principles of Consolidation : The consolidated financial statements of the Company include the accounts of its subsidiaries. The JV underlies the noncontrolling interest reflected in the consolidated financial statements until late 2020 when the Bank purchased the remaining interest as discussed in Note 1 above under Nature of Banking Activities and Subsidiaries. The consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and conform to general practices within the banking industry. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements. Results of operations of companies purchased, if any, are included from the date of acquisition. Operating Segment : The consolidated income of the Company is derived principally from the Bank, which conducts lending (primarily commercial-based loans, as well as residential and consumer loans) and deposit gathering (including other banking- and deposit-related products and services, such as ATMs, safe deposit boxes, check cashing, wires, and debit cards) to businesses, consumers and governmental units principally in its trade area of northeastern and central Wisconsin, and Menominee, Michigan, trust services, brokerage services (delivered through the Bank and Nicolet Advisory), and the support to deliver, fund and manage all such banking and wealth management services to its customer base. The individual contribution from wealth management was not significant to the consolidated balance sheet or net income for 2020, 2019, or 2018. While the chief operating decision makers monitor the revenue streams of the various products and services, and evaluate costs, balance sheet positions and quality, all such products, services and activities are directly or indirectly related to the business of community banking, with no regular, formal or material segment delineations. Operations are managed and financial performance is evaluated on a company-wide basis, and accordingly, all the financial service operations are considered by management to be aggregated in one reportable operating segment. Use of 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, 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-loans, 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. Business Combinations : The Company accounts for business combinations under the acquisition method of accounting in accordance with Accounting Standards Codification (“ASC”) 805, Business Combinations (“ASC 805”). The Company recognizes the full fair value of the assets acquired and liabilities assumed and immediately expenses transaction costs. If the amount of consideration exceeds the fair value of assets purchased less the fair value of liabilities assumed, goodwill is recorded. Alternatively, if the amount by which the fair value of assets purchased exceeds the fair value of liabilities assumed and consideration paid, a gain (“bargain purchase gain”) is recorded. Fair values are subject to refinement for up to one year after the closing date of an acquisition as information relative to closing date fair values becomes available. Results of operations of the acquired business are included in the statements of income from the effective date of the acquisition. Additional information regarding recent acquisitions is provided in Note 2. Cash and Cash Equivalents : For purposes of the consolidated statements of cash flows, cash and cash equivalents include cash and due from banks, interest-earning deposits in other banks with original maturities of less than 90 days, if any, and federal funds sold. The Bank maintains amounts in due from banks which, at times, may exceed federally insured limits. Management monitors these correspondent relationships. The Bank has not experienced any losses in such accounts. The Bank may have restrictions on cash and due from banks as it is required to maintain certain vault cash and reserve balances with the Federal Reserve Bank to meet specific reserve requirements. At December 31, 2020, no reserve balance was required with the Federal Reserve Bank (as the Federal Reserve’s board authorized a reduction to the reserve requirement ratios to 0% effective March 26, 2020 to provide monetary stimulus in response to the economic disruptions resulting from the pandemic), while at December 31, 2019, the required reserve balance was approximately $6.0 million, of which there was sufficient cash to cover the reserve requirement. In addition, cash and cash equivalents includes restricted cash of $1.9 million and $1.3 million pledged as collateral on an interest rate swap at December 31, 2020 and 2019, respectively. 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. Securities classified as AFS are carried at fair value, with unrealized gains or losses, net of related deferred income taxes, reported as increases or decreases in accumulated other comprehensive income. Realized gains or losses on sales of securities AFS (using the specific identification method) are included in the consolidated statements of income under asset gains (losses), net. Premiums and discounts are amortized or accreted into interest income over the estimated life of the related securities using the effective interest method. Management evaluates securities AFS in unrealized loss positions on a quarterly basis to determine whether the decline in fair value below the amortized cost 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 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 must be recognized in net income with a corresponding adjustment to the security’s amortized cost basis rather than through the establishment on an ACL. See Note 3 for additional disclosures on AFS securities. Other Investments : Other investments include equity securities with readily determinable fair values, “restricted” equity securities, and private company securities. At December 31, 2020, other investments included $3.6 million of equity securities with readily determinable fair values, $20.2 million of “restricted“ equity securities, and $3.9 million of private company securities. As a member of the Federal Reserve Bank System and the Federal Home Loan Bank (“FHLB”) System, the Bank is required to maintain an investment in the capital stock of these entities. These equity securities are “restricted” in that they can only be sold back to the respective institutions or another member institution at par. Therefore, they are less liquid than other exchange traded equity securities. As no ready market exists for these stocks, and they have no quoted market value, these investments are carried at cost. Also included are investments in other private companies that do not have quoted market prices, which are carried at cost less impairment charges, if any. Management’s evaluation of these other investments for impairment includes consideration of the financial condition and other available relevant information of the issuer. Loans Held for Sale : Loans originated and intended for sale in the secondary market are carried at the lower of cost or estimated fair value as determined on an aggregate basis and generally consist of current production of certain fixed-rate residential first mortgages. The amount by which cost exceeds fair value is recorded as a valuation allowance and charged to earnings. Changes, if any, in the valuation allowance are included in earnings in the period in which the change occurs. As of December 31, 2020 and 2019, no valuation allowance was necessary. Loans held for sale may be sold servicing retained or servicing released, and are generally sold without recourse. The carrying value of mortgage loans sold with servicing retained is reduced by the amount allocated to the servicing right at the time of sale. Gains and losses on sales of mortgage loans held for sale are included in earnings in mortgage income, net. 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 amount outstanding, net of deferred loan fees and costs, and any direct principal charge-off. 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 4 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 on the acquisition date. 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 4 for additional information and disclosures on loans. Prior to January 1, 2020, the Company initially classified acquired loans as either purchased credit impaired (“PCI”) loans (i.e., loans that reflect credit deterioration since origination and for which it was probable at acquisition that the Company would 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. Allowance for Credit Losses - Loans : The ACL-Loans represents management’s estimate of expected credit losses over the lifetime of the loan based on loans 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. Actual credit losses, net of recoveries, are deducted from the ACL-Loans. Loans are charged-off when management believes that the collectability of the principal is unlikely. Subsequent recoveries, if any, are credited to the ACL-Loans. A provision for credit losses, which is a charge against income, is recorded to bring the ACL-Loans to a level that, in management’s judgment, is appropriate to absorb expected credit losses in the loan portfolio. Prior to January 1, 2020, the Company used an incurred loss impairment model to estimate the ACL-Loans. 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. Effective January 1, 2020, the Company uses a current expected credit loss model (“CECL”) to estimate the ACL-Loans. 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 and other credit-deteriorated 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. To assess the overall appropriateness of the ACL-Loans, management applies an allocation methodology which focuses on evaluation of qualitative and environmental factors, including but not limited to: (i) evaluation of facts and issues related to specific loans; (ii) management's ongoing review and grading of the loan portfolio; (iii) consideration of historical loan loss and delinquency experience on each portfolio segment; (iv) trends in past due and nonaccrual loans; (v) the risk characteristics of the various loan segments; (vi) changes in the size and character of the loan portfolio; (vii) concentrations of loans to specific borrowers or industries; (viii) existing economic conditions; (ix) the fair value of underlying collateral; and (x) other qualitative and quantitative factors which could affect expected credit losses. Assessing these numerous factors involves significant judgment. Management allocates the ACL-Loans by pools of risk within each loan portfolio segment. The allocation methodology consists of the following components. First, a specific reserve is established for individually evaluated PCD and other credit-deteriorated loans, which management defines as nonaccrual credit relationships over $250,000, collateral dependent loans, and other loans with evidence of credit deterioration. The specific reserve in the ACL-Loans for these credit deteriorated loans is equal to the aggregate collateral or discounted cash flow shortfall. Management allocates the ACL-Loans with historical loss rates by loan segment. The loss factors are measured on a quarterly basis and applied to each loan segment based on current loan balances and projected for their expected remaining life. Next, management allocates the ACL-Loans using the qualitative and environmental factors mentioned above. Consideration is given to those current qualitative or environmental factors that are likely to cause estimated credit losses at the evaluation date to differ from the historical loss experience of each loan segment. Lastly, management considers reasonable and supportable forecasts to assess the collectability of future cash flows. See Note 4 for additional information and disclosures on the ACL-Loans. Allocations to the ACL-Loans may be made for specific loans but the entire ACL-Loans is available for any loan that, in management’s judgment, should be charged-off or for which an actual loss is realized. The allowance analysis is reviewed by the Board on a quarterly basis in compliance with internal and regulatory requirements. Credit-Related Financial Instruments : In the ordinary course of business the Company has entered into financial instruments consisting of commitments to extend credit, financial standby letters of credit, and performance standby letters of credit. Financial standby letters of credit are issued specifically to facilitate commerce and typically result in the commitment being drawn on when the underlying transaction is consummated between the customer and the third party, while performance standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of the underlying contract with the third party. Such financial instruments are recorded in the consolidated financial statements when they are funded. See Note 13 for additional information and disclosures on credit-related financial instruments. Transfers of Financial Assets : Transfers of financial assets, primarily in loan participation activities, are accounted for as sales only when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (1) the assets have been isolated from the Company, (2) the transferee obtains the right (free of conditions that constrain it from taking advantage of the right) to pledge or exchange the transferred assets, and (3) the Company does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity or the ability to unilaterally cause the holder to return assets. Premises and Equipment : Premises and equipment are stated at cost less accumulated depreciation and amortization. Premises and equipment from acquisitions were recorded at estimated fair value on the respective dates of acquisition. Depreciation is computed on a straight-line basis over the estimated useful lives of the related assets. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the improvements or the terms of the related leases. Maintenance and repairs are expensed as incurred. See Note 5 for additional information on premises and equipment. Estimated useful lives of new premises and equipment generally range as follows: Building and improvements 25 – 40 years Leasehold improvements 5 – 15 years Furniture and equipment 3 – 10 years Operating Leases : The Company accounts for its operating leases in accordance with ASC 842, Leases (“ASC 842”), which requires lessees to record almost all leases on the balance sheet as a right-of-use (“ROU”) asset and lease liability. The operating lease ROU asset represents the right to use an underlying asset during the lease term (included in accrued interest receivable and other assets on the consolidated balance sheets), while the operating lease liability represents the obligation to make lease payments arising from the lease (included in accrued interest payable and other liabilities Other Real Estate Owned (“OREO”) : OREO acquired through partial or total satisfaction of loans or bank facilities no longer in use are carried at fair value less estimated costs to sell. Any write-down in the carrying value of loans or vacated bank premises at the time of transfer to OREO is charged to the ACL-Loans or to write-down of assets, respectively. OREO properties acquired in conjunction with acquisition transactions were recorded at fair value on the date of acquisition. Any subsequent write-downs to reflect current fair value, as well as gains or losses on disposition and revenues and expenses incurred to hold and maintain such properties, are treated as period costs. At December 31, 2020 and 2019, OREO was $3.6 million and $1.0 million, respectively. Goodwill and Other Intangibles : Goodwill represents the excess of the purchase price over the fair value of the net identifiable assets acquired. Goodwill is not amortized but, instead, is subject to impairment tests on at least an annual basis or more frequently if certain events or circumstances occur. Other intangibles include core deposit intangibles (which represent the value of acquired customer core deposit bases) and customer list intangibles. The core deposit intangibles have an estimated finite life, are amortized on an accelerated basis over a 10-year period, and are subject to periodic impairment evaluation. The customer list intangibles have finite lives, are amortized on a straight-line basis to expense over their initial weighted average life of approximately 12 years as of acquisition, and are subject to periodic impairment evaluation. See Note 6 for additional information on goodwill and other intangibles. Management periodically reviews the carrying value of its intangible assets to determine if any impairment has occurred, in which case an impairment charge would be recorded as an expense in the period of impairment, or whether changes in circumstances have occurred that would require a revision to the remaining useful life which would impact expense prospectively. In making such determination, management evaluates whether there are any adverse qualitative factors indicating that an impairment may exist, as well as the performance, on an undiscounted basis, of the underlying operations or assets which give rise to the intangible. The Company’s annual assessments resulted in a $0.8 million impairment charge on goodwill in late 2019 for a change in business strategy, while no other impairment was indicated on the remaining goodwill and other intangibles for 2020 or 2019. Mortgage Servicing Rights (“MSRs”) : The Company sells originated residential mortgages into the secondary market and retains the right to service the loans sold. A mortgage servicing right asset (liability) is capitalized upon sale of such loans with the offsetting effect recorded as a gain (loss) on sale of loan in earnings (included in mortgage income, net), representing the then-current estimated fair value of future net cash flows expected to be realized for performing the servicing activities. MSRs when purchased (including MSRs purchased in acquisitions) are initially recorded at their then-estimated fair value. As the Company has not elected to measure any class of servicing assets under the fair value method, the Company utilizes the amortization method. MSRs are amortized in proportion to and over the period of estimated net servicing income, with the amortization charged to earnings (included in mortgage income, net). MSRs are carried at the lower of initial capitalized amount, net of accumulated amortization, or estimated fair value, and are included in other assets in the consolidated balance sheets. Loan servicing fee income for servicing loans is typically based on a contractual percentage of the outstanding principal and is recorded as income when earned (included in mortgage income, net with less material late fees and ancillary fees related to loan servicing). The Company periodically evaluates its MSRs for impairment. At each reporting date impairment is assessed based on estimated fair value using estimated prepayment speeds of the underlying mortgage loans serviced and stratifications based on the risk characteristics of the underlying loans (predominantly loan type and note interest rate). The value of MSRs is adversely affected when mortgage interest rates decline and mortgage loan prepayments increase. A valuation allowance is established through a charge to earnings (included in mortgage income, net) to the extent the amortized cost of the MSRs exceeds the estimated fair value by stratification. If it is later determined that all or a portion of the temporary impairment no longer exists for a stratification, the valuation is reduced through a recovery to earnings, though not beyond the net amortized cost carried. An other-than-temporary impairment (i.e., recoverability is considered remote when considering interest rates and loan payoff activity) is recognized as a write-down of the MSRs and the related valuation allowance (to the extent a valuation allowance is available) and then against earnings. A direct write-down permanently reduces the carrying value of the MSRs and valuation allowance, precluding subsequent recoveries. A valuation allowance of $1 million was recorded for 2020, while no valuation allowance or impairment charge was recorded for 2019. See Note 6 for additional information on MSRs. Bank-owned Life Insurance (“BOLI”) : The Company owns BOLI on certain executives and employees. BOLI balances are recorded at their cash surrender values. Changes in the cash surrender values and death proceeds exceeding carrying values are included in BOLI income. Short-term Borrowings : Short-term borrowings consist primarily of overnight Federal funds purchased and securities sold under agreements to repurchase (“repos”), or other short-term borrowing arrangements with an original maturity of one year or less. Repos are with commercial deposit customers, and are treated as financing activities carried at the amounts that will be subsequently repurchased as specified in the respective agreements. Repos generally mature within one Stock-based Compensation : Stock-based payments to employees, including grants of restricted stock or stock options, are valued at fair value of the award on the date of grant and expensed on a straight-line basis as compensation expense over the applicable vesting period. A Black-Scholes model is utilized to estimate the fair value of stock options and the quoted market price of the Company’s stock at the date of grant is used to estimate the fair value of restricted stock awards. See Note 10 for additional information on stock-based compensation. Income Taxes : The Company files a consolidated federal income tax return and a combined state income tax return (both

ACQUISITIONS

ACQUISITIONS	12 Months Ended
	Dec. 31, 2020
Business Combinations [Abstract]
ACQUISITIONS	ACQUISITIONS Completed Acquisitions: Advantage Community Bancshares, Inc. (“Advantage”) : On August 21, 2020, Nicolet completed its merger with Advantage, pursuant to the terms of the definitive merger agreement dated March 2, 2020, whereby Advantage merged with and into Nicolet, and Advantage Community Bank, the wholly owned bank subsidiary of Advantage, was merged with and into the Company's banking subsidiary, Nicolet National Bank. Advantage’s four branches in Dorchester, Edgar, Mosinee, and Wausau opened as Nicolet National Bank branches on August 24, 2020, expanding our presence in Central Wisconsin and the Wausau area. Due to the small size of the transaction, terms of the all-cash deal were not disclosed. Upon consummation, Advantage added total assets of approximately $172 million (representing 4% of Nicolet’s then pre-merger asset size), loans of $88 million, deposits of $141 million, core deposit intangible of $1 million, and goodwill of $12 million. Choice Bancorp, Inc. (“Choice”) : On November 8, 2019, the Company consummated its merger with Choice, pursuant to the terms of the Agreement and Plan of Merger dated June 26, 2019, (the “Choice Merger Agreement”), whereby Choice (at 12% of Nicolet’s then pre-merger asset size) was merged with and into Nicolet, and Choice Bank, the wholly owned bank subsidiary of Choice, was merged with and into the Bank. The system integration was completed, and the two branches of Choice opened on November 12, 2019, as Nicolet National Bank branches, expanding its presence in the Oshkosh marketplace. The Company closed its legacy Oshkosh location concurrently with the consummation of the Choice merger. The purpose of the merger was to continue Nicolet’s interest in strategic growth, consistent with its plan to improve profitability through efficiency, leverage the strengths of each bank across the combined customer base, and add shareholder value. With the merger, Nicolet became the leading community bank to serve the Oshkosh marketplace. Pursuant to the Choice Merger Agreement, the final purchase price consisted of issuing 1,184,102 shares of the Company’s common stock (given the final stock-for-stock exchange ratio of 0.497, and not exchanging the Choice shares owned by the Company immediately prior to the time of the merger), for common stock consideration of $79.8 million (based on $67.39 per share, the volume weighted average closing price of the Company’s common stock over the preceding 30 trading day period) plus cash consideration of $1.7 million. Approximately $0.2 million in direct stock issuance costs for the merger were incurred and charged against additional paid-in capital. Upon consummation, Choice added $457 million in assets, including $348 million in loans, $289 million in deposits, $1.7 million in core deposit intangible, and $45 million of goodwill. The Company accounted for the transaction under the acquisition method of accounting, and thus, the financial position and results of operations of Choice prior to the consummation date were not included in the accompanying consolidated financial statements. The accounting required assets purchased and liabilities assumed to be recorded at their respective estimated fair values at the date of acquisition. Terminated Acquisition: Commerce Financial Holdings, Inc. (“Commerce”) : On February 17, 2020, Nicolet entered into a definitive merger agreement (“Merger Agreement”) with Commerce pursuant to which Nicolet would acquire Commerce and its wholly owned bank subsidiary, Commerce State Bank. On May 18, 2020, Nicolet and Commerce announced a mutual agreement to terminate their Merger Agreement. Nicolet paid Commerce $0.5 million and surrendered its $0.1 million of Commerce common stock.

SECURITIES AVAILABLE FOR SALE

SECURITIES AVAILABLE FOR SALE	12 Months Ended
	Dec. 31, 2020
Debt Securities, Available-for-sale [Abstract]
SECURITIES AVAILABLE FOR SALE	SECURITIES AVAILABLE FOR SALE Amortized cost and fair value of securities available for sale are summarized as follows. December 31, 2020 (in thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Fair Fair Value as % of Total U.S. government agency securities $ 63,162 $ 289 $ — $ 63,451 12 % State, county and municipals 226,493 5,386 11 231,868 43 % Mortgage-backed securities 156,148 6,425 78 162,495 30 % Corporate debt securities 76,073 5,450 — 81,523 15 % $ 521,876 $ 17,550 $ 89 $ 539,337 100 % December 31, 2019 (in thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Fair Fair Value as % of Total U.S. government agency securities $ 16,516 $ 4 $ 60 $ 16,460 4 % State, county and municipals 155,501 1,049 157 156,393 35 % Mortgage-backed securities 193,223 2,492 697 195,018 43 % Corporate debt securities 78,009 3,422 — 81,431 18 % $ 443,249 $ 6,967 $ 914 $ 449,302 100 % All mortgage-backed securities included in the tables above were issued by U.S. government agencies and corporations. Securities AFS with a fair value of $146 million and $166 million as of December 31, 2020 and 2019, respectively, were pledged as collateral on public deposits and for other purposes as required or permitted by law. Accrued interest on securities AFS totaled $2.3 million and $2.2 million at December 31, 2020 and 2019, respectively, and is included in accrued interest receivable and other assets on the consolidated balance sheets. The following tables present gross unrealized losses and the related estimated fair value of investment securities AFS for which an allowance for credit losses has not been recorded, aggregated by investment category and the length of time the individual securities have been in a continuous unrealized loss position. December 31, 2020 Less than 12 months 12 months or more Total ($ in thousands) Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Number of Securities State, county and municipals $ 5,181 $ 11 $ — $ — $ 5,181 $ 11 9 Mortgage-backed securities 10,612 71 492 7 11,104 78 22 $ 15,793 $ 82 $ 492 $ 7 $ 16,285 $ 89 31 December 31, 2019 Less than 12 months 12 months or more Total ($ in thousands) Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Number of Securities U.S. government agency securities $ 1,035 $ 2 $ 11,091 $ 58 $ 12,126 $ 60 6 State, county and municipals 22,451 132 7,605 25 30,056 157 56 Mortgage-backed securities 49,626 245 47,271 452 96,897 697 150 $ 73,112 $ 379 $ 65,967 $ 535 $ 139,079 $ 914 212 The Company evaluates securities AFS in unrealized loss positions to determine whether the 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. As of December 31, 2020, no allowance for credit losses on securities AFS was recognized. The Company does not consider its securities AFS with unrealized losses to be attributable to credit-related factors as the unrealized losses in each category have occurred as a result of changes in noncredit-related factors such as changes in interest rates, market spreads, and market conditions subsequent to purchase, not credit deterioration. Furthermore, the Company does not have the intent to sell any of these securities AFS and believes that it is more likely than not that we will not have to sell any such securities before a recovery of cost. There were no other-than-temporary impairment charges recognized in earnings on securities AFS during 2019 or 2018. The amortized cost and fair value of securities AFS by contractual maturity are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties; as this is particularly inherent in mortgage-backed securities, these securities are not included in the maturity categories below. See Note 17 for additional information on the Company’s fair value measurements. December 31, 2020 (in thousands) Amortized Cost Fair Value Due in less than one year $ 85,317 $ 85,712 Due in one year through five years 168,302 174,975 Due after five years through ten years 97,662 100,445 Due after ten years 14,447 15,710 365,728 376,842 Mortgage-backed securities 156,148 162,495 Securities AFS $ 521,876 $ 539,337 Proceeds and realized gains / losses from the sale of securities AFS were as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Gross gains $ 395 $ 152 $ — Gross losses — (174) (212) Gains (losses) on sales of securities AFS, net $ 395 $ (22) $ (212) Proceeds from sales of securities AFS $ 19,045 $ 23,405 $ 5,280

LOANS, ALLOWANCE FOR LOAN LOSSE

LOANS, ALLOWANCE FOR LOAN LOSSES, AND CREDIT QUALITY	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY	LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY Loans : The loan composition was as follows. December 31, 2020 December 31, 2019 (in thousands) Amount % of Total Amount % of Total Commercial & industrial $ 750,718 27 % $ 806,189 31 % Paycheck Protection Program (“PPP”) loans 186,016 7 — — Owner-occupied commercial real estate (“CRE”) 521,300 19 496,372 19 Agricultural 109,629 4 95,450 4 CRE investment 460,721 16 443,218 17 Construction & land development 131,283 5 92,970 4 Residential construction 41,707 1 54,403 2 Residential first mortgage 444,155 16 432,167 17 Residential junior mortgage 111,877 4 122,771 5 Retail & other 31,695 1 30,211 1 Loans 2,789,101 100 % 2,573,751 100 % Less ACL-Loans 32,173 13,972 Loans, net $ 2,756,928 $ 2,559,779 ACL-Loans to loans 1.15 % 0.54 % Accrued interest on loans totaled $7 million at both December 31, 2020 and December 31, 2019, and is included in accrued interest receivable and other assets on the consolidated balance sheets. See Note 1 for the Company’s accounting policy on loans and the allowance for credit losses. Allowance for Credit Losses-Loans : The majority of the Company’s loans, commitments, and letters of credit have been granted to customers in the Company’s market area. Although the Company has a diversified loan portfolio, the credit risk in the loan portfolio is largely influenced by general economic conditions and trends of the counties and markets in which the debtors operate, and the resulting impact on the operations of borrowers or on the value of underlying collateral, if any. A roll forward of the allowance for credit losses - loans was as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Beginning balance $ 13,972 $ 13,153 $ 12,653 Adoption of CECL 8,488 — — Initial PCD ACL 797 — — Total impact for adoption of CECL 9,285 — — Provision for credit losses 10,300 1,200 1,600 Charge-offs (1,689) (927) (1,213) Recoveries 305 546 113 Net (charge-offs) recoveries (1,384) (381) (1,100) Ending balance $ 32,173 $ 13,972 $ 13,153 The following table presents the balance and activity in the ACL-Loans by portfolio segment. Year Ended December 31, 2020 (in thousands) Commercial Owner- Agricultural CRE Construction & land Residential Residential Residential Retail Total ACL-Loans * Beginning balance $ 5,471 $ 3,010 $ 579 $ 1,600 $ 414 $ 368 $ 1,669 $ 517 $ 344 $ 13,972 Adoption of CECL 2,962 1,249 361 1,970 51 124 1,286 351 134 8,488 Initial PCD ACL 797 — — — — — — — — 797 Provision 3,106 2,062 455 2,061 519 (71) 1,809 151 208 10,300 Charge-offs (812) (530) — (190) — — (2) — (155) (1,689) Recoveries 120 81 — — — — 11 67 26 305 Net (charge-offs) recoveries (692) (449) — (190) — — 9 67 (129) (1,384) Ending balance $ 11,644 $ 5,872 $ 1,395 $ 5,441 $ 984 $ 421 $ 4,773 $ 1,086 $ 557 $ 32,173 As % of ACL-Loans 36 % 18 % 4 % 17 % 3 % 1 % 15 % 4 % 2 % 100 % * The PPP loans are fully guaranteed by the SBA; thus, no ACL-Loans has been allocated to these loans. For comparison purposes, the following table presents the balance and activity in the ACL-Loans by portfolio segment for the prior year-end period. Year Ended December 31, 2019 (in thousands) Commercial Owner- Agricultural CRE Construction & land Residential Residential Residential Retail Total ACL-Loans Beginning balance $ 5,271 $ 2,847 $ 422 $ 1,470 $ 510 $ 211 $ 1,646 $ 472 $ 304 $ 13,153 Provision (61) 254 157 130 (96) 383 9 86 338 1,200 Charge-offs (159) (93) — — — (226) (22) (80) (347) (927) Recoveries 420 2 — — — — 36 39 49 546 Net (charge-offs) recoveries 261 (91) — — — (226) 14 (41) (298) (381) Ending balance $ 5,471 $ 3,010 $ 579 $ 1,600 $ 414 $ 368 $ 1,669 $ 517 $ 344 $ 13,972 As % of ACL-Loans 39 % 22 % 4 % 11 % 3 % 3 % 12 % 4 % 2 % 100 % The ACL-Loans at December 31, 2020 was estimated using the current expected credit loss model, while the ACL-Loans at December 31, 2019 was estimated using the incurred loss model. See Note 1 for the Company’s accounting policy on loans and the allowance for credit losses. A loan is considered to be collateral dependent when, based upon management’s assessment, the borrower is experiencing financial difficulty and repayment is expected to be provided substantially through the operation or sale of the collateral. For collateral dependent loans, expected credit losses are based on the fair value of the collateral at the balance sheet date, with consideration for estimated selling costs if satisfaction of the loan depends on the sale of the collateral. The following table presents collateral dependent loans by portfolio segment and collateral type, including those loans with and without a related allowance allocation as of December 31, 2020. December 31, 2020 Collateral Type (in thousands) Real Estate Other Business Assets Total Without an Allowance With an Allowance Allowance Allocation Commercial & industrial $ — $ 2,195 $ 2,195 $ 501 $ 1,694 $ 1,241 PPP loans — — — — — — Owner-occupied CRE 3,519 — 3,519 3,519 — — Agricultural 584 797 1,381 1,378 3 3 CRE investment 1,474 — 1,474 1,474 — — Construction & land development 308 — 308 308 — — Residential construction — — — — — — Residential first mortgage — — — — — — Residential junior mortgage — — — — — — Retail & other — — — — — — Total loans $ 5,885 $ 2,992 $ 8,877 $ 7,180 $ 1,697 $ 1,244 The following table presents impaired loans and their respective allowance for credit loss allocations at December 31, 2019, as determined in accordance with historical accounting guidance. December 31, 2019 (in thousands) Recorded Unpaid Principal Related Average Interest Income Commercial & industrial $ 5,932 $ 7,950 $ 625 $ 5,405 $ 1,170 Owner-occupied CRE 3,430 4,016 — 3,677 256 Agricultural 2,134 2,172 116 2,311 37 CRE investment 2,426 2,790 — 2,497 364 Construction & land development 382 382 — 460 — Residential construction — — — — — Residential first mortgage 2,357 2,629 — 2,412 178 Residential junior mortgage 218 349 — 224 58 Retail & other 12 12 — 12 — Total $ 16,891 $ 20,300 $ 741 $ 16,998 $ 2,063 Past Due and Nonaccrual Loans : The following tables present past due loans by portfolio segment. December 31, 2020 (in thousands) 30-89 Days Past 90 Days & Over Current Total Commercial & industrial $ — $ 2,646 $ 748,072 $ 750,718 PPP loans — — 186,016 186,016 Owner-occupied CRE — 1,869 519,431 521,300 Agricultural 7 1,830 107,792 109,629 CRE investment — 1,488 459,233 460,721 Construction & land development — 327 130,956 131,283 Residential construction — — 41,707 41,707 Residential first mortgage 613 823 442,719 444,155 Residential junior mortgage 43 384 111,450 111,877 Retail & other 102 88 31,505 31,695 Total loans $ 765 $ 9,455 $ 2,778,881 $ 2,789,101 Percent of total loans — % 0.4 % 99.6 % 100.0 % December 31, 2019 (in thousands) 30-89 Days Past 90 Days & Over Current Total Commercial & industrial $ 1,729 $ 6,249 $ 798,211 $ 806,189 Owner-occupied CRE 112 3,311 492,949 496,372 Agricultural — 1,898 93,552 95,450 CRE investment — 1,073 442,145 443,218 Construction & land development 2,063 20 90,887 92,970 Residential construction 302 — 54,101 54,403 Residential first mortgage 2,736 1,090 428,341 432,167 Residential junior mortgage 217 480 122,074 122,771 Retail & other 110 1 30,100 30,211 Total loans $ 7,269 $ 14,122 $ 2,552,360 $ 2,573,751 Percent of total loans 0.3 % 0.5 % 99.2 % 100.0 % The following table presents nonaccrual loans by portfolio segment. The nonaccrual loans without a related allowance for credit losses have been reflected in the collateral dependent loans table above. Total Nonaccrual Loans (in thousands) December 31, 2020 % to Total December 31, 2019 % to Total Commercial & industrial $ 2,646 28 % $ 6,249 44 % PPP loans — — — — Owner-occupied CRE 1,869 20 3,311 23 Agricultural 1,830 19 1,898 14 CRE investment 1,488 16 1,073 8 Construction & land development 327 3 20 — Residential construction — — — — Residential first mortgage 823 9 1,090 8 Residential junior mortgage 384 4 480 3 Retail & other 88 1 1 — Nonaccrual loans $ 9,455 100 % $ 14,122 100 % Percent of total loans 0.4 % 0.5 % Credit Quality Information : The following table presents total loans by risk categories and year of origination. December 31, 2020 Amortized Cost Basis by Origination Year (in thousands) 2020 2019 2018 2017 2016 Prior Revolving Revolving to Term TOTAL Commercial & industrial (a) Grades 1-4 $ 348,274 $ 121,989 $ 98,920 $ 72,027 $ 21,613 $ 39,454 $ 183,858 $ — $ 886,135 Grade 5 1,416 2,239 4,486 527 1,638 4,151 18,994 — 33,451 Grade 6 69 19 735 5,315 29 32 1,923 — 8,122 Grade 7 334 1,126 1,389 663 122 3,103 2,289 — 9,026 Total $ 350,093 $ 125,373 $ 105,530 $ 78,532 $ 23,402 $ 46,740 $ 207,064 $ — $ 936,734 Owner-occupied CRE Grades 1-4 $ 90,702 $ 74,029 $ 78,013 $ 52,911 $ 45,042 $ 150,624 $ 870 $ — $ 492,191 Grade 5 42 623 1,349 7,541 1,102 5,842 — — 16,499 Grade 6 — — — 1,710 — 706 — — 2,416 Grade 7 2,987 675 176 835 — 5,521 — — 10,194 Total $ 93,731 $ 75,327 $ 79,538 $ 62,997 $ 46,144 $ 162,693 $ 870 $ — $ 521,300 Agricultural Grades 1-4 $ 13,719 $ 5,652 $ 7,580 $ 9,745 $ 2,613 $ 32,702 $ 21,513 $ — $ 93,524 Grade 5 1,034 — 701 169 644 6,131 356 — 9,035 Grade 6 — — — 329 390 — — — 719 Grade 7 — — 26 110 1,111 5,042 62 — 6,351 Total $ 14,753 $ 5,652 $ 8,307 $ 10,353 $ 4,758 $ 43,875 $ 21,931 $ — $ 109,629 CRE investment Grades 1-4 $ 82,518 $ 78,841 $ 40,881 $ 69,643 $ 31,541 $ 137,048 $ 5,255 $ — $ 445,727 Grade 5 — — 47 1,284 1,828 9,073 — — 12,232 Grade 6 — — — 796 — — — — 796 Grade 7 — — — — — 1,966 — — 1,966 Total $ 82,518 $ 78,841 $ 40,928 $ 71,723 $ 33,369 $ 148,087 $ 5,255 $ — $ 460,721 Construction & land development Grades 1-4 $ 67,578 $ 30,733 $ 15,209 $ 2,204 $ 2,083 $ 7,266 $ 3,675 $ — $ 128,748 Grade 5 — 373 660 545 — 23 455 — 2,056 Grade 6 — — — — — — — — — Grade 7 — — — — — 479 — — 479 Total $ 67,578 $ 31,106 $ 15,869 $ 2,749 $ 2,083 $ 7,768 $ 4,130 $ — $ 131,283 Residential construction Grades 1-4 $ 31,687 $ 9,185 $ 395 $ 121 $ — $ 264 $ — $ — $ 41,652 Grade 5 — — — 55 — — — — 55 Grade 6 — — — — — — — — — Grade 7 — — — — — — — — — Total $ 31,687 $ 9,185 $ 395 $ 176 $ — $ 264 $ — $ — $ 41,707 Residential first mortgage Grades 1-4 $ 146,744 $ 64,013 $ 40,388 $ 41,245 $ 41,274 $ 103,094 $ 287 $ 5 $ 437,050 Grade 5 — 925 2,245 256 364 1,714 — — 5,504 Grade 6 — — — — — — — — — Grade 7 — 437 197 16 9 942 — — 1,601 Total $ 146,744 $ 65,375 $ 42,830 $ 41,517 $ 41,647 $ 105,750 $ 287 $ 5 $ 444,155 Residential junior mortgage Grades 1-4 $ 4,936 $ 4,338 $ 3,663 $ 1,060 $ 869 $ 3,131 $ 91,816 $ 1,648 $ 111,461 Grade 5 — — — — — 32 — — 32 Grade 6 — — — — — — — — — Grade 7 — — — 27 — 232 125 — 384 Total $ 4,936 $ 4,338 $ 3,663 $ 1,087 $ 869 $ 3,395 $ 91,941 $ 1,648 $ 111,877 Retail & other Grades 1-4 $ 8,083 $ 5,213 $ 1,942 $ 1,676 $ 752 $ 1,339 $ 12,602 $ — $ 31,607 Grade 5 — — — — — — — — — Grade 6 — — — — — — — — — Grade 7 16 — 22 — — 50 — — 88 Total $ 8,099 $ 5,213 $ 1,964 $ 1,676 $ 752 $ 1,389 $ 12,602 $ — $ 31,695 Total loans $ 800,139 $ 400,410 $ 299,024 $ 270,810 $ 153,024 $ 519,961 $ 344,080 $ 1,653 $ 2,789,101 (a) For purposes of this table, the $186 million net carrying value of PPP loans were originated in 2020, have a Pass risk grade (Grades 1-4) and have been included with the Commercial & industrial loan category. The following tables present total loans by risk categories. December 31, 2020 (in thousands) Grades 1-4 Grade 5 Grade 6 Grade 7 Total Commercial & industrial $ 700,119 $ 33,451 $ 8,122 $ 9,026 $ 750,718 PPP loans 186,016 — — — 186,016 Owner-occupied CRE 492,191 16,499 2,416 10,194 521,300 Agricultural 93,524 9,035 719 6,351 109,629 CRE investment 445,727 12,232 796 1,966 460,721 Construction & land development 128,748 2,056 — 479 131,283 Residential construction 41,652 55 — — 41,707 Residential first mortgage 437,050 5,504 — 1,601 444,155 Residential junior mortgage 111,461 32 — 384 111,877 Retail & other 31,607 — — 88 31,695 Total loans $ 2,668,095 $ 78,864 $ 12,053 $ 30,089 $ 2,789,101 Percent of total loans 95.7 % 2.8 % 0.4 % 1.1 % 100.0 % December 31, 2019 (in thousands) Grades 1-4 Grade 5 Grade 6 Grade 7 Total Commercial & industrial $ 765,073 $ 20,199 $ 7,663 $ 13,254 $ 806,189 Owner-occupied CRE 464,661 20,855 953 9,903 496,372 Agricultural 77,082 6,785 3,275 8,308 95,450 CRE investment 430,794 8,085 2,578 1,761 443,218 Construction & land development 90,523 2,213 15 219 92,970 Residential construction 53,286 1,117 — — 54,403 Residential first mortgage 424,044 4,677 668 2,778 432,167 Residential junior mortgage 122,249 35 — 487 122,771 Retail & other 30,210 — — 1 30,211 Total loans $ 2,457,922 $ 63,966 $ 15,152 $ 36,711 $ 2,573,751 Percent of total loans 95.5 % 2.5 % 0.6 % 1.4 % 100.0 % An internal loan review function rates loans using a grading system based on different risk categories. Loans with a Substandard grade are considered to have a greater risk of loss and may be assigned allocations for loss based on specific review of the weaknesses observed in the individual credits. Such loans are constantly monitored by the loan review function to ensure early identification of any deterioration. A description of the loan risk categories used by the Company follows. Grades 1-4, Pass: Credits exhibit adequate cash flows, appropriate management and financial ratios within industry norms and/or are supported by sufficient collateral. Some credits in these rating categories may require a need for monitoring but elements of concern are not severe enough to warrant an elevated rating. Grade 5, Watch: Credits with this rating are adequately secured and performing but are being monitored due to the presence of various short-term weaknesses which may include unexpected, short-term adverse financial performance, managerial problems, potential impact of a decline in the entire industry or local economy and delinquency issues. Loans to individuals or loans supported by guarantors with marginal net worth or collateral may be included in this rating category. Grade 6, Special Mention: Credits with this rating have potential weaknesses that, without the Company’s attention and correction may result in deterioration of repayment prospects. These assets are considered Criticized Assets. Potential weaknesses may include adverse financial trends for the borrower or industry, repeated lack of compliance with Company requests, increasing debt to net worth, serious management conditions and decreasing cash flow. Grade 7, Substandard: Assets with this rating are characterized by the distinct possibility the Company will sustain some loss if deficiencies are not corrected. All foreclosures, liquidations, and nonaccrual loans are considered to be categorized in this rating, regardless of collateral sufficiency. Troubled Debt Restructurings: At December 31, 2020, there were eleven loans classified as troubled debt restructurings with a current outstanding balance of $5.5 million (including $3.4 million on nonaccrual and $2.1 million performing) and a pre-modification balance of $6.5 million. In comparison, at December 31, 2019, there were five loans classified as troubled debt restructurings with an outstanding balance of $1.1 million (all nonaccrual) and a pre-modification balance of $1.4 million. There were no loans which were classified as troubled debt restructurings during the previous twelve months that subsequently defaulted during 2020. As of December 31, 2020, there were no commitments to lend additional funds to debtors whose terms have been modified in troubled debt restructurings.

PREMISES AND EQUIPMENT

PREMISES AND EQUIPMENT	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
PREMISES AND EQUIPMENT	PREMISES AND EQUIPMENT Premises and equipment, less accumulated depreciation and amortization, is summarized as follows. (in thousands) December 31, 2020 December 31, 2019 Land $ 6,344 $ 7,418 Land improvements 3,950 3,865 Building and improvements 54,989 50,818 Leasehold improvements 4,381 4,580 Furniture and equipment 22,701 20,262 92,365 86,943 Less accumulated depreciation and amortization 32,421 30,474 Premises and equipment, net $ 59,944 $ 56,469 Depreciation and amortization expense was $4.4 million in 2020, $3.8 million in 2019, and $4.4 million in 2018. The Company and certain of its subsidiaries are obligated under non-cancelable operating leases for facilities, certain of which provide for rental adjustments based upon increases in cost of living adjustments and other indices. Rent expense under leases totaled $1.0 million in 2020, $1.2 million in 2019, and $1.4 million in 2018. See Note 1 for the Company’s accounting policy on premises and equipment. Nicolet leases space under non-cancelable operating lease agreements for certain bank and nonbank branch facilities with remaining lease terms of 1 to 10 years. Certain lease arrangements contain extension options which typically range from 5 to 10 years at the then fair market rental rates. The lease asset and liability considers renewal options when they are reasonably certain of being exercised. See Note 1 for the Company’s accounting policy on operating leases. A summary of net lease cost and selected other information related to operating leases was as follows. Years Ended ($ in thousands) December 31, 2020 December 31, 2019 Net lease cost: Operating lease cost $ 834 $ 970 Variable lease cost 169 233 Net lease cost $ 1,003 $ 1,203 Selected other operating lease information: Weighted average remaining lease term (years) 5.1 4.3 Weighted average discount rate 2.0 % 2.5 % The following table summarizes the maturity of remaining lease liabilities. Years Ending December 31, (in thousands) 2021 $ 920 2022 780 2023 497 2024 391 2025 106 Thereafter 507 Total future minimum lease payments 3,201 Less: amount representing interest (63) Present value of net future minimum lease payments $ 3,138 During 2020, the Company permanently closed eight branch locations (five owned locations and three leased locations) given changing customer needs, partly from the pandemic. These closures resulted in accelerated depreciation of $0.5 million (recorded to occupancy, equipment and office expense), a $1.0 million lease termination charge (recorded to other expense), and a $1.0 million write-down upon transfer of the owned locations to OREO (recorded to asset gains (losses), net). During 2019, a $0.7 million lease termination charge was recorded to other expense due to the closure of a branch, concurrent with the consummation date of the Choice merger.

GOODWILL AND OTHER INTANGIBLES

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS	GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS Management periodically reviews the carrying value of its intangible assets to determine if any impairment has occurred, in which case an impairment charge would be recorded as an expense in the period of impairment. During 2020, management considered the potential impact of the COVID-19 pandemic on the valuation of our franchise value, stability of deposits, and of the wealth client base, underlying our goodwill, core deposit intangibles, and customer list intangibles, and determined no impairments were indicated. However, the impacts of the COVID-19 pandemic, which began in March 2020, continue to evolve. A summary of goodwill and other intangibles was as follows. (in thousands) December 31, 2020 December 31, 2019 Goodwill $ 163,151 $ 151,198 Core deposit intangibles 8,837 10,897 Customer list intangibles 3,365 3,872 Other intangibles 12,202 14,769 Goodwill and other intangibles, net $ 175,353 $ 165,967 Goodwill : Goodwill is not amortized but, instead, is subject to impairment tests on at least an annual basis or more frequently if certain events or circumstances occur. During 2020, goodwill increased due to the Advantage acquisition, while during 2019, goodwill increased from the Choice acquisition and impairment was recognized on goodwill initially recorded in 2008 for a change in business strategy. See Note 1 for the Company’s accounting policy for goodwill and see Note 2 for additional information on the Company’s acquisitions. (in thousands) December 31, 2020 December 31, 2019 Goodwill: Goodwill at beginning of year $ 151,198 $ 107,366 Acquisition 11,953 44,594 Impairment — (762) Goodwill at end of year $ 163,151 $ 151,198 Other intangibles : Other intangible assets, consisting of core deposit intangibles and customer list intangibles, are amortized over their estimated finite lives. During 2020, core deposit intangibles increased due to the Advantage acquisition, while during 2019, core deposit intangibles increased from the Choice acquisition. See Note 1 for the Company’s accounting policy for other intangibles and see Note 2 for additional information on the Company’s acquisitions. (in thousands) December 31, 2020 December 31, 2019 Core deposit intangibles: Gross carrying amount $ 31,715 $ 30,715 Accumulated amortization (22,878) (19,818) Net book value $ 8,837 $ 10,897 Additions during the period $ 1,000 $ 1,700 Amortization during the period $ 3,060 $ 3,365 Customer list intangibles: Gross carrying amount $ 5,523 $ 5,523 Accumulated amortization (2,158) (1,651) Net book value $ 3,365 $ 3,872 Amortization during the period $ 507 $ 507 Mortgage servicing rights : A summary of the changes in the MSR asset was as follows. (in thousands) December 31, 2020 December 31, 2019 MSR asset: MSR asset at beginning of year $ 5,919 $ 3,749 Capitalized MSR 5,256 2,876 MSR asset acquired 529 160 Amortization during the period (1,474) (866) MSR asset at end of year $ 10,230 $ 5,919 Valuation allowance at beginning of year $ — $ — Additions (1,000) — Valuation allowance at end of year $ (1,000) $ — MSR asset, net $ 9,230 $ 5,919 Fair value of MSR asset at end of period $ 9,276 $ 8,420 Residential mortgage loans serviced for others $ 1,250,206 $ 847,756 Net book value of MSR asset to loans serviced for others 0.74 % 0.70 % The Company periodically evaluates its mortgage servicing rights asset for impairment. A valuation allowance of $1.0 million was recorded for 2020, while no valuation allowance was recorded for 2019. See Note 1 for the Company’s accounting policy for MSRs, see Note 2 for additional information on the Company’s acquisitions, and see Note 17 for additional information on the fair value of the MSR asset. The following table shows the estimated future amortization expense for amortizing intangible assets and the MSR asset. The projections are based on existing asset balances, the current interest rate environment and prepayment speeds as of December 31, 2020. The actual amortization expense the Company recognizes in any given period may be significantly different depending upon acquisition or sale activities, changes in interest rates, prepayment speeds, market conditions, regulatory requirements and events or circumstances that indicate the carrying amount of an asset may not be recoverable. (in thousands) Core deposit Customer list MSR asset Years Ending December 31, 2021 $ 2,643 $ 507 $ 1,771 2022 2,150 507 1,740 2023 1,633 483 1,635 2024 1,130 449 1,225 2025 670 449 876 Thereafter 611 970 2,983 Total $ 8,837 $ 3,365 $ 10,230

DEPOSITS

DEPOSITS	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
DEPOSITS	DEPOSITS At December 31, 2020, the scheduled maturities of time deposits were as follows. Years Ending December 31, (in thousands) 2021 $ 335,433 2022 118,898 2023 114,432 2024 37,169 2025 17,544 Thereafter 997 Total time deposits $ 624,473 Time deposits of $250,000 or more were $55.6 million and $91.2 million at December 31, 2020 and 2019, respectively.

SHORT AND LONG-TERM BORROWINGS

SHORT AND LONG-TERM BORROWINGS	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
SHORT AND LONG-TERM BORROWINGS	SHORT AND LONG-TERM BORROWINGS Short-Term Borrowings: The Company did not have any short-term borrowings (borrowing with an original contractual maturity of one year or less) outstanding at December 31, 2020 or 2019. Long-Term Borrowings: The components of long-term borrowings (borrowing with an original contractual maturity greater than one year) were as follows. (in thousands) December 31, 2020 December 31, 2019 FHLB advances $ 29,000 $ 25,061 Junior subordinated debentures 24,869 30,575 Subordinated notes — 11,993 Total long-term borrowings $ 53,869 $ 67,629 PPP Liquidity Facility (“PPPLF”) : To support the effectiveness of the PPP loans, the Federal Reserve introduced the PPPLF to extend credit to financial institutions that made PPP loans, with the related PPP loans used as collateral on the borrowings. The PPPLF borrowings had a fixed interest rate of 0.35% and a maturity date equal to the maturity date of the related PPP loans, with the PPP loans maturing either two or five years from the origination date of the PPP loan. The Company received PPPLF funds of $344 million during second quarter 2020 which was subsequently repaid in full during fourth quarter 2020, given the level of all other funding. FHLB Advances : The FHLB advances bear fixed rates, require interest-only monthly payments, and have maturity dates through March 2027. The weighted average rate of the FHLB advances was 0.73% and 1.57% at December 31, 2020 and 2019, respectively. The FHLB advances are collateralized by a blanket lien on qualifying first mortgages, home equity loans, multi-family loans and certain farmland loans which had a pledged balance of $272.9 million and $273.5 million at December 31, 2020 and 2019, respectively. The following table shows the maturity schedule of the FHLB advances as of December 31, 2020. Maturing in: (in thousands) 2021 $ 4,000 2022 — 2023 — 2024 — 2025 5,000 Thereafter 20,000 $ 29,000 The Company has a $10 million line of credit with a third party bank, bearing a variable rate of interest and quarterly payments of interest only. At December 31, 2020, the interest rate was based on the Prime Rate plus a 0.25% margin, and subject to a floor rate of 3.50%, while at December 31, 2019, the interest rate was based on one-month LIBOR plus a 2.25% margin and subject to a floor rate of 3.25%. At December 31, 2020, the available line was $10 million. The outstanding balance was zero at December 31, 2020 and 2019, and the line was not used during 2020 or 2019. Junior Subordinated Debentures : The following table shows the breakdown of junior subordinated debentures. Interest on all debentures is current. Any applicable discounts (initially recorded to carry an acquired debenture at its then estimated fair value) are being accreted to interest expense over the remaining life of the debentures. All the debentures below are currently callable and may be redeemed in part or in full, at par, plus any accrued but unpaid interest. On December 31, 2020, the Company redeemed in full its 2004 Nicolet Bankshares Statutory Trust junior subordinated debentures. Junior Subordinated Debentures (in thousands) Maturity Par 12/31/2020 Unamortized Discount 12/31/2020 Carrying Value 12/31/2019 Carrying Value 2004 Nicolet Bankshares Statutory Trust (1) 7/15/2034 $ — $ — $ — $ 6,186 2005 Mid-Wisconsin Financial Services, Inc. (2) 12/15/2035 10,310 (2,972) 7,338 7,138 2006 Baylake Corp. (3) 9/30/2036 16,598 (3,647) 12,951 12,715 2004 First Menasha Bancshares, Inc. (4) 3/17/2034 5,155 (575) 4,580 4,536 Total $ 32,063 $ (7,194) $ 24,869 $ 30,575 (1) The interest rate is 8.00% fixed. (2) The debentures, assumed in April 2013 as the result of an acquisition, have a floating rate of the three-month LIBOR plus 1.43%, adjusted quarterly. The interest rates were 1.65% and 3.32% as of December 31, 2020 and 2019, respectively. (3) The debentures, assumed in April 2016 as a result of an acquisition, have a floating rate of the three-month LIBOR plus 1.35%, adjusted quarterly. The interest rates were 1.59% and 3.31% as of December 31, 2020 and 2019, respectively. (4) The debentures, assumed in April 2017 as the result of an acquisition, have a floating rate of the three-month LIBOR plus 2.79%, adjusted quarterly. The interest rate was 3.02% and 4.69% as of December 31, 2020 and 2019, respectively. Each of the junior subordinated debentures was issued to an underlying statutory trust (the “statutory trusts”), which issued trust preferred securities and common securities and used the proceeds from the issuance of the common and the trust preferred securities to purchase the junior subordinated debentures of the Company. The debentures represent the sole asset of the statutory trusts. All of the common securities of the statutory trusts are owned by the Company. The statutory trusts are not included in the consolidated financial statements. The net effect of all the documents entered into with respect to the trust preferred securities is that the Company, through payments on its debentures, is liable for the distributions and other payments required on the trust preferred securities. At December 31, 2020 and 2019, $23.9 million and $29.4 million, respectively, of trust preferred securities qualify as Tier 1 capital. Subordinates Notes : In 2015, the Company placed an aggregate of $12 million in subordinated Notes in private placements with certain accredited investors. All Notes were issued with 10-year maturities, had a fixed annual interest rate of 5% payable quarterly, and were callable on or after the fifth anniversary of their respective issuances dates. On November 16, 2020, the Company fully redeemed the subordinated Notes.

EMPLOYEE AND DIRECTOR BENEFIT P

EMPLOYEE AND DIRECTOR BENEFIT PLANS	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
EMPLOYEE AND DIRECTOR BENEFIT PLANS	EMPLOYEE AND DIRECTOR BENEFIT PLANS The Company sponsors two deferred compensation plans, one for certain key management employees and another for directors. Under the management plan, employees designated by the Board of Directors may elect to defer compensation and the Company may at its discretion make nonelective contributions on behalf of one or more eligible plan participants. Upon retirement, termination of employment or at their election, the employee shall become entitled to receive the deferred amounts plus earnings thereon. The liability for the cumulative employee contributions and earnings thereon at December 31, 2020 and 2019 totaled approximately $1.5 million and $0.9 million, respectively, and is included in other liabilities on the consolidated balance sheets. The Company made discretionary contributions totaling $1.4 million and $1.8 million during 2020 and 2019, respectively, to selected recipients, which vested immediately and were fully expensed upon grant. Under the director plan, participating directors may defer up to 100% of their Board compensation towards the purchase of Company common stock at market prices on a quarterly basis that is held in a Rabbi Trust and distributed when each such participating director ends his or her board service. During 2020 and 2019, the director plan purchased 2,561 and 3,769 shares of Company common stock valued at approximately $149,000 and $220,000, respectively. Common stock valued at approximately $20,157 (and representing 282 shares) and $33,000 (and representing 672 shares) was distributed to past directors during 2020 and 2019, respectively. The common stock outstanding and the related director deferred compensation liability are offsetting

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION The Company may grant stock options and restricted stock under its stock-based compensation plans to certain officers, employees and directors. These plans are administered by a committee of the Board of Directors. The Company’s stock-based compensation plans at December 31, 2020 are described below. 2011 Long-Term Incentive Plan (“2011 LTIP”) : The Company’s 2011 LTIP, as subsequently amended with shareholder approval, has reserved 3,000,000 shares of the Company’s common stock for potential stock-based awards. This plan provides for certain stock-based awards such as, but not limited to, stock options, stock appreciation rights and restricted common stock, as well as cash performance awards. As of December 31, 2020, approximately 1.3 million shares were available for grant under this plan. 2002 Stock Incentive Plan : The Company’s 2002 Stock Incentive Plan, as subsequently amended with shareholder approval, reserved a total of 1,175,000 shares of the Company’s common stock for potential stock options. This plan became fully utilized in 2012 and no further awards may be granted under this plan. Acquired Equity Incentive Plan : In 2016, the Company assumed sponsorship of an equity incentive plan of an acquired company to allow for that company’s already granted awards that became exercisable upon acquisition to be honored. No further awards may be granted under this assumed plan. In general, for stock option grants the exercise price will not be less than the fair value of the Company’s common stock on the date of grant, the options will become exercisable based upon vesting terms determined by the committee, and the options will expire ten years after the date of grant. In general, for restricted stock grants the shares are issued at the fair value of the Company’s common stock on the date of grant, are restricted as to transfer, but are not restricted as to dividend payments or voting rights, and the transfer restrictions lapse over time, depending upon vesting terms provided for in the grant and contingent upon continued employment. A Black-Scholes model is utilized to estimate the fair value of stock option grants. See Note 1 for the Company’s accounting policy on stock-based compensation. The weighted average assumptions used in the model for valuing stock option grants were as follows. 2020 2019 2018 Dividend yield — % — % — % Expected volatility 25 % 25 % 25 % Risk-free interest rate 1.35 % 1.75 % 2.61 % Expected average life 7 years 7 years 7 years Weighted average per share fair value of options $ 20.55 $ 21.30 $ 17.36 A summary of the Company’s stock option activity is summarized below. Stock Options Option Shares Weighted Average Weighted Average Remaining Life (Years) Aggregate Intrinsic Value (in thousands) Outstanding – December 31, 2017 1,643,255 $ 39.82 Granted 15,500 52.76 Exercise of stock options * (70,556) 21.52 Forfeited (6,500) 39.43 Outstanding – December 31, 2018 1,581,699 $ 40.77 7.4 $ 13,825 Granted 203,000 69.69 Exercise of stock options * (337,428) 24.15 Forfeited (3,538) 27.43 Outstanding – December 31, 2019 1,443,733 $ 48.75 7.4 $ 36,428 Granted 54,500 69.44 Exercise of stock options * (60,773) 26.51 Forfeited — — Outstanding – December 31, 2020 1,437,460 $ 50.47 6.6 $ 23,840 Exercisable – December 31, 2020 800,310 $ 46.18 6.1 $ 16,310 *The terms of the stock option agreements permit having a number of shares of stock withheld, the fair market value of which as of the date of exercise is sufficient to satisfy the exercise price and/or tax withholding requirements, and accordingly 18,952 shares, 142,752 shares, and 6,411 shares were surrendered during 2020, 2019, and 2018, respectively. Intrinsic value represents the amount by which the fair value of the underlying stock exceeds the exercise price of the stock options. The intrinsic value of options exercised in 2020, 2019, and 2018 was approximately $2.5 million, $13.9 million, and $2.2 million, respectively. The following options were outstanding at December 31, 2020. Number of Shares Weighted Average Weighted Average Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable $13.73 – $30.00 82,013 77,963 $ 21.98 $ 22.27 3.1 3.2 $30.01 – $40.00 146,297 116,197 35.82 35.52 5.4 5.3 $40.01 – $50.00 801,150 478,350 48.86 48.86 6.4 6.4 $50.01 – $60.00 160,500 88,200 56.08 56.18 7.0 6.9 $60.01 – $73.52 247,500 39,600 70.16 70.01 8.9 8.9 1,437,460 800,310 $ 50.47 $ 46.18 6.6 6.1 A summary of the Company’s restricted stock activity is summarized below. Restricted Stock Restricted Shares Weighted Average Grant Outstanding – December 31, 2017 30,920 $ 34.26 Granted 18,256 52.55 Vested * (19,661) 43.58 Forfeited (3) 16.50 Outstanding – December 31, 2018 29,512 $ 39.37 Granted 12,498 67.59 Vested * (19,081) 51.77 Forfeited (408) 16.50 Outstanding – December 31, 2019 22,521 $ 44.94 Granted 19,672 60.29 Vested * (23,268) 50.90 Forfeited — — Outstanding – December 31, 2020 18,925 $ 53.57 *The terms of the restricted stock agreements permit the surrender of shares to the Company upon vesting in order to satisfy applicable tax withholding at the minimum statutory withholding rate, and accordingly 4,733 shares, 4,688 shares, and 3,948 shares were surrendered during 2020, 2019, and 2018, respectively.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
	Dec. 31, 2020
Stockholders' Equity Note [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY The Board of Directors has authorized the repurchase of Nicolet’s outstanding common stock through its common stock repurchase program. During 2020, $40.5 million was utilized to repurchase and cancel over 646,700 common shares at a weighted average price of $62.69. As of December 31, 2020, there remained $20.4 million authorized under the repurchase program to be utilized from time-to-time to repurchase common shares in the open market, through block transactions or in private transactions. See Note 14, “Related Party Transactions” for additional information on common stock repurchases in private transactions with related parties. On November 8, 2019, in connection with its acquisition of Choice, the Company issued 1,184,102 shares of its common stock for consideration of $79.8 million plus cash consideration of $1.7 million for outstanding stock options. Approximately $0.2 million in direct stock issuance costs for the merger were incurred and charged against additional paid-in capital. See Note 2 for additional information on the Company’s acquisitions.

INCOME TAXES

INCOME TAXES	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The current and deferred amounts of income tax expense were as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Current $ 29,764 $ 15,353 $ 14,967 Deferred (9,288) 1,105 (1,521) Income tax expense $ 20,476 $ 16,458 $ 13,446 The differences between the income tax expense recognized and the amount computed by applying the statutory federal income tax rate of 21% to the income before income tax expense, less noncontrolling interest, for the years ended as indicated are included in the following table. Years Ended December 31, (in thousands) 2020 2019 2018 Tax on pretax income, less noncontrolling interest, at statutory rates $ 16,926 $ 14,931 $ 11,441 State income taxes, net of federal effect 5,030 3,672 3,308 Tax-exempt interest income (527) (609) (574) Non-deductible interest disallowance 14 29 30 Increase in cash surrender value life insurance (738) (573) (508) Non-deductible business entertainment 170 189 156 Stock-based employee compensation (839) (2,347) (232) Non-deductible compensation 272 3,122 — Sale of UFS (109) (2,176) — Other, net 277 220 (175) Income tax expense $ 20,476 $ 16,458 $ 13,446 The net deferred tax asset includes the following amounts of deferred tax assets and liabilities. (in thousands) December 31, 2020 December 31, 2019 Deferred tax assets: ACL-Loans $ 9,328 $ 4,985 Net operating loss carryforwards 1,692 1,808 Credit carryforwards — 43 Compensation 5,822 3,477 Purchase of noncontrolling interest 2,112 — Other 2,949 2,830 Other real estate 538 201 Total deferred tax assets 22,441 13,344 Deferred tax liabilities: Premises and equipment (1,577) (1,390) Prepaid expenses (1,010) (778) Investment securities (451) (755) Core deposit and other intangibles (1,777) (2,836) Purchase accounting adjustments to liabilities (1,969) (2,375) MSR asset (2,269) (1,391) Other (282) — Unrealized gain on securities AFS (4,959) (1,879) Total deferred tax liabilities (14,294) (11,404) Net deferred tax assets $ 8,147 $ 1,940 A valuation allowance is required if it is more likely than not that some portion of the deferred tax asset will not be realized. At December 31, 2020 and 2019, no valuation allowance was determined to be necessary. At December 31, 2020, the Company had a federal and state net operating loss carryforward of $3.3 million and $15.7 million, respectively. The entire federal and state net operating loss carryforwards were the result of the Company’s acquisitions. The federal and state net operating loss carryovers resulting from the acquisitions have been included in the IRC section 382 limitation calculation and are being limited to the overall amount expected to be realized.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES The Company is party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit, financial guarantees, and standby letters of credit. Such commitments may involve, to varying degrees, elements of credit risk in excess of amounts recognized on the consolidated balance sheets. See Note 1 for the Company’s accounting policy on commitments and contingencies. The Company’s exposure to credit loss in the event of nonperformance by the other party to the financial instruments for commitments to extend credit and standby letters of credit is represented by the contractual amount of those instruments. The Company uses the same credit policies in making commitments and issuing letters of credit as they do for on-balance sheet instruments. A summary of the contract or notional amount of the Company’s exposure to off-balance sheet risk was as follows. (in thousands) December 31, 2020 December 31, 2019 Commitments to extend credit $ 950,287 $ 773,555 Financial standby letters of credit 8,241 10,730 Performance standby letters of credit 8,366 8,469 Interest rate lock commitments to originate residential mortgage loans held for sale and forward commitments to sell residential mortgage loans held for sale are considered derivative instruments (“mortgage derivatives”) and the contractual amounts were $113 million and $20 million, respectively, at December 31, 2020. In comparison, interest rate lock commitments to originate residential mortgage loans held for sale and forward commitments to sell residential mortgage loans held for sale totaled $43 million and $16 million, respectively, at December 31, 2019. The net fair value of these mortgage derivatives combined was a net loss of $0.2 million at December 31, 2020, compared to a net gain of $0.1 million at December 31, 2019. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the contract. Commercial-related commitments to extend credit represented 78% and 74% of the total year-end commitments for 2020 and 2019, respectively, and were predominantly commercial lines of credit that carry a term of one year or less. The commitments generally have fixed expiration dates or other termination clauses and may require payment of a fee. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. Financial and performance standby letters of credit are conditional commitments issued to guarantee the performance of a customer to a third party. Financial standby letters of credit are issued specifically to facilitate commerce and typically result in the commitment being drawn on when the underlying transaction is consummated between the customer and the third party, while performance standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of the underlying contract with the third party. Both of these guarantees are primarily issued to support public and private borrowing arrangements and, generally, have terms of one year or less. The credit risk involved in issuing letters of credit is essentially the same as that involved in extending loan facilities to customers. The Company holds collateral, which may include accounts receivable, inventory, property, equipment, and income-producing properties, supporting those commitments if deemed necessary. In the event the customer does not perform in accordance with the terms of the agreement with the third-party, the Company would be required to fund the commitment. The maximum potential amount of future payments the Company could be required to make is represented by the contractual amount. If the commitment is funded, the Company would be entitled to seek recovery from the customer. At December 31, 2020 and 2019, no amounts have been recorded as liabilities for the Company’s potential obligations under these guarantees. The Company has federal funds lines available with other financial institutions where funds may be borrowed on a short-term basis at the market rate in effect at the time of the borrowing. Federal funds lines of $175 million were available at both December 31, 2020 and 2019. In the normal course of business, the Company is involved in various legal proceedings. In the opinion of management, any liability resulting from such proceedings would not have a material adverse effect on the consolidated financial statements.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS The Company conducts transactions, in the normal course of business, with its directors and officers, including companies in which they have a beneficial interest. The Company is required to disclose material related party transactions, other than certain compensation arrangements, entered into in the normal course of business. It is the Company’s policy to comply with federal regulations that require that these transactions with directors and executive officers be made on substantially the same terms as those prevailing at the time made for comparable transactions to other persons. Related party loans totaled approximately $89 million and $86 million at December 31, 2020 and 2019, respectively. Nicolet has an active common stock repurchase program that allows for the repurchase of common stock in the open market, through block transactions, or in private transactions. During 2020, Nicolet repurchased common stock in private transactions from two executives under this repurchase program, including 5,851 shares for $0.4 million (or an average cost per share of $71.45) from Robert B. Atwell and 5,852 shares for $0.4 million (or an average cost per share of $71.45) from Michael E. Daniels. In comparison, during 2019, Nicolet repurchased common stock in private transactions from two executives, including 32,415 shares for $2.2 million (or an average cost per share of $69.21) from Robert B. Atwell and 33,993 shares for $2.2 million (or an average cost per share of $64.02) from Michael E. Daniels. These private transactions were made in conjunction with large stock option exercises by the executives. See Note 10 for additional information on stock option activity and see Note 11 for additional information on the common stock repurchase program. As described in Note 1, the Company had a 50% ownership in a joint venture with the Firm in connection with the Company’s headquarters facility. The Firm is considered a related party, as one of its principals is a Board member and shareholder of the Company. Effective December 31, 2020, the Bank purchased the 50% ownership interest from the Firm for $8 million, to improve efficiencies in process and organizational structure, and to reflect that the Bank had expanded to occupy the majority of the building. Thus, at December 31, 2020, the Bank was the sole owner and managing member of the JV, with the JV operating as a wholly owned subsidiary of the Bank solely to hold the headquarters facility. Prior to this purchase, the Bank incurred approximately $1.3 million, $1.2 million, and $1.1 million in annual rent expense to the JV during 2020, 2019, and 2018, respectively.

ASSET GAINS (LOSSES), NET

ASSET GAINS (LOSSES), NET	12 Months Ended
	Dec. 31, 2020
Assets Gains (Losses), Net [Abstract]
ASSET GAINS (LOSSES), NET	ASSET GAINS (LOSSES), NET Components of the net gains (losses) on assets are as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Gains (losses) on sales of securities AFS, net $ 395 $ (22) $ (212) Gains (losses) on equity securities, net (987) 1,115 77 Gains (losses) on sales of OREO, net 157 (88) 1,032 Write-downs of OREO (1,040) (300) (120) Write-down of other investment (100) (100) — Gains (losses) on sales of other investments, net — 7,442 187 Gains (losses) on sales or dispositions of other assets, net (230) (150) 205 Asset gains (losses), net $ (1,805) $ 7,897 $ 1,169

REGULATORY CAPITAL REQUIREMENTS

REGULATORY CAPITAL REQUIREMENTS	12 Months Ended
	Dec. 31, 2020
Regulatory Capital Requirements Under Banking Regulations [Abstract]
REGULATORY CAPITAL REQUIREMENTS	REGULATORY CAPITAL REQUIREMENTS The Company (on a consolidated basis) and the Bank are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company’s and Bank’s financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company and Bank must meet specific capital guidelines that involve quantitative measures of their assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk-weightings, and other factors. Prompt corrective action provisions are not applicable to bank holding companies. Quantitative measures established by regulation to ensure capital adequacy require the Company and Bank to maintain minimum amounts and ratios of Total, Tier 1 and common equity Tier 1 (“CET1”) capital (as defined in the regulations) to risk-weighted assets (as defined), and Tier 1 capital (as defined) to average assets (as defined). Management believes the Company and the Bank met all capital adequacy requirements to which they are subject as of December 31, 2020 and 2019. As of December 31, 2020 and 2019, the most recent notifications from the regulatory agencies categorized the Bank as well-capitalized under the regulatory framework for prompt corrective action. To be categorized as well-capitalized, an institution must maintain minimum Total risk-based, Tier 1 risk-based, CET1 risk-based and Tier 1 leverage ratios as set forth in the following table. There are no conditions or events since these notifications that management believes have changed the Bank’s category. The Company’s and the Bank’s actual regulatory capital amounts and ratios are presented in the following table. Actual For Capital Adequacy To Be Well Capitalized Under Prompt Corrective Action Provisions (2) (in thousands) Amount Ratio (1) Amount Ratio (1) Amount Ratio (1) December 31, 2020 Company Total risk-based capital $ 406,325 12.9 % $ 252,683 8.0 % Tier 1 risk-based capital 385,068 12.2 189,512 6.0 Common equity Tier 1 capital 361,162 11.4 142,134 4.5 Leverage 385,068 9.0 170,402 4.0 Bank Total risk-based capital $ 351,081 11.2 % $ 251,769 8.0 % $ 314,711 10.0 % Tier 1 risk-based capital 329,824 10.5 188,826 6.0 251,769 8.0 Common equity Tier 1 capital 329,824 10.5 141,620 4.5 204,562 6.5 Leverage 329,824 7.8 170,025 4.0 212,532 5.0 December 31, 2019 Company Total risk-based capital $ 404,573 13.4 % $ 241,333 8.0 % Tier 1 risk-based capital 378,608 12.6 181,000 6.0 Common equity Tier 1 capital 348,454 11.6 135,750 4.5 Leverage 378,608 11.9 127,036 4.0 Bank Total risk-based capital $ 323,432 10.8 % $ 240,551 8.0 % $ 300,688 10.0 % Tier 1 risk-based capital 309,460 10.3 180,413 6.0 240,551 8.0 Common equity Tier 1 capital 309,460 10.3 135,310 4.5 195,447 6.5 Leverage 309,460 9.8 126,660 4.0 158,325 5.0 (1) The Total risk-based capital ratio is defined as Tier 1 capital plus tier 2 capital divided by total risk-weighted assets. The Tier 1 risk-based capital ratio is defined as Tier 1 capital divided by total risk-weighted assets. CET1 risk-based capital ratio is defined as Tier 1 capital, with deductions for goodwill and other intangible assets (other than mortgage servicing assets), net of associated deferred tax liabilities, and limitations on the inclusion of deferred tax assets, mortgage servicing assets and investments in other financial institutions, in each case as provided further in the rules, divided by total risk-weighted assets. The Leverage ratio is defined as Tier 1 capital divided by the most recent quarter’s average total assets as adjusted. (2) Prompt corrective action provisions are not applicable at the bank holding company level. Dividends declared by the Bank that exceed the retained net income for the most current year plus retained net income for the preceding two years must be approved by Federal regulatory agencies. At December 31, 2020, the Bank could pay dividends of approximately $11 million to the Company without seeking regulatory approval.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Fair value represents the estimated price at which an orderly transaction to sell an asset or transfer a liability would take place between market participants at the measurement date under current market conditions (i.e., an exit price concept), and is a market-based measurement versus an entity-specific measurement. The Company records and/or discloses financial instruments on a fair value basis. These financial assets and financial liabilities are measured at fair value in three levels, based on the markets in which the assets and liabilities are traded and the observability of the assumptions used to determine fair value. These levels are: • Level 1 - quoted market prices in active markets for identical assets or liabilities that a company has the ability to access at the measurement date • Level 2 - inputs other than quoted prices included in Level 1 that are observable for the asset or liability, either directly or indirectly • Level 3 – significant unobservable inputs for the asset or liability, which are typically based on an entity’s own assumptions, as there is little, if any, related market activity In instances where the fair value measurement is based on inputs from different levels, the level within which the entire fair value measurement will be categorized is based on the lowest level input that is significant to the fair value measurement in its entirety. This assessment of the significance of an input requires management judgment. Recurring basis fair value measurements: The following table presents the balances of assets and liabilities measured at fair value on a recurring basis for the periods presented. (in thousands) Fair Value Measurements Using Measured at Fair Value on a Recurring Basis: Total Level 1 Level 2 Level 3 December 31, 2020 U.S. government agency securities $ 63,451 $ — $ 63,451 $ — State, county and municipals 231,868 — 231,868 — Mortgage-backed securities 162,495 — 162,495 — Corporate debt securities 81,523 — 78,393 3,130 Securities AFS $ 539,337 $ — $ 536,207 $ 3,130 Other investments (equity securities) $ 3,567 $ 3,567 $ — $ — December 31, 2019 U.S. government agency securities $ 16,460 $ — $ 16,460 $ — State, county and municipals 156,393 — 156,393 — Mortgage-backed securities 195,018 — 195,018 — Corporate debt securities 81,431 — 78,301 3,130 Securities AFS $ 449,302 $ — $ 446,172 $ 3,130 Other investments (equity securities) $ 3,375 $ 3,375 $ — $ — The following is a description of the valuation methodologies used by the Company for the Securities AFS and equity securities measured at fair value on a recurring basis, noted in the tables above. Where quoted market prices on securities exchanges are available, the investments are classified as Level 1. Level 1 investments primarily include exchange-traded equity securities. If quoted market prices are not available, fair value is generally determined using prices obtained from independent pricing vendors who use pricing models (with typical inputs including benchmark yields, reported trades for similar securities, issuer spreads or relationship to other benchmark quoted securities), or discounted cash flows, and are classified as Level 2. Examples of these investments include U.S. government agency securities, mortgage-backed securities, obligations of state, county and municipals, and certain corporate debt securities. Finally, in certain cases where there is limited activity or less transparency around inputs to the estimated fair value, investments are classified within Level 3 of the hierarchy. Examples of these include private corporate debt securities, which are primarily trust preferred security investments. At December 31, 2020 and 2019, it was determined that carrying value was the best approximation of fair value for these Level 3 securities, based primarily on the internal analysis on these securities. The following table presents the changes in Level 3 securities AFS measured at fair value on a recurring basis. (in thousands) Years Ended Level 3 Fair Value Measurements: December 31, 2020 December 31, 2019 Balance at beginning of year $ 3,130 $ 8,490 Acquired balances — 300 Paydowns/Sales/Settlements — (5,660) Balance at end of year $ 3,130 $ 3,130 Nonrecurring basis fair value measurements: The following table presents the Company’s assets measured at fair value on a nonrecurring basis, aggregated by the level in the fair value hierarchy within which those measurements fall. (in thousands) Fair Value Measurements Using Measured at Fair Value on a Nonrecurring Basis: Total Level 1 Level 2 Level 3 December 31, 2020 Collateral dependent loans $ 7,633 $ — $ — $ 7,633 OREO 3,608 — — 3,608 MSR asset 9,276 — — 9,276 December 31, 2019 Impaired loans $ 16,150 $ — $ — $ 16,150 OREO 1,000 — — 1,000 MSR asset 8,420 — — 8,420 The following is a description of the valuation methodologies used by the Company for the items noted in the table above. For individually evaluated collateral dependent and impaired loans, the amount of impairment is based upon the present value of expected future cash flows discounted at the loan’s effective interest rate, the estimated fair value of the underlying collateral for collateral dependent loans, or the estimated liquidity of the note. For OREO, the fair value is based upon the estimated fair value of the underlying collateral adjusted for the expected costs to sell. To estimate the fair value of the MSR asset, the underlying serviced loan pools are stratified by interest rate tranche and term of the loan, and a valuation model is used to calculate the present value of the expected future cash flows for each stratum. The valuation model incorporates assumptions that market participants would use in estimating future net servicing income, such as costs to service, a discount rate, ancillary income, default rates and losses, and prepayment speeds. Although some of these assumptions are based on observable market data, other assumptions are based on unobservable estimates of what market participants would use to measure fair value. Financial instruments: The carrying amounts and estimated fair values of the Company's financial instruments are shown below. December 31, 2020 (in thousands) Carrying Estimated Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 802,859 $ 802,859 $ 802,859 $ — $ — Certificates of deposit in other banks 29,521 31,053 — 31,053 — Securities AFS 539,337 539,337 — 536,207 3,130 Other investments 27,619 27,619 3,567 20,155 3,897 Loans held for sale 21,450 22,329 — 22,329 — Loans, net 2,756,928 2,834,452 — — 2,834,452 BOLI 83,262 83,262 83,262 — — MSR asset 9,230 9,276 — — 9,276 Financial liabilities: Deposits $ 3,910,399 $ 3,917,121 $ — $ — $ 3,917,121 Long-term borrowings 53,869 53,859 — 29,488 24,371 December 31, 2019 (in thousands) Carrying Estimated Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 182,059 $ 182,059 $ 182,059 $ — $ — Certificates of deposit in other banks 19,305 19,310 — 19,310 — Securities AFS 449,302 449,302 — 446,172 3,130 Other investments 24,072 24,072 3,375 16,759 3,938 Loans held for sale 2,706 2,753 — 2,753 — Loans, net 2,559,779 2,593,110 — — 2,593,110 BOLI 78,140 78,140 78,140 — — MSR asset 5,919 8,420 — — 8,420 Financial liabilities: Deposits $ 2,954,453 $ 2,956,229 $ — $ — $ 2,956,229 Long-term borrowings 67,629 66,816 — 25,075 41,741 The carrying value of certain assets and liabilities such as cash and cash equivalents, BOLI, nonmaturing deposits, and short-term borrowings, approximate their estimated fair value. For those financial instruments not previously disclosed, the following is a description of the valuation methodologies used. Certificates of deposits in other banks: Fair values are estimated using discounted cash flow analysis based on current interest rates being offered by instruments with similar terms and represents a Level 2 measurement. Other investments : The valuation methodologies utilized for the exchange-traded equity securities are discussed under “Recurring basis fair value measurements” above. The carrying amount of Federal Reserve Bank and FHLB stock is a reasonably accepted fair value estimate given their restricted nature. Fair value is the redeemable (carrying) value based on the redemption provisions of the instruments which is considered a Level 2 measurement. The carrying amount of the remaining other investments (particularly common stocks of companies or other banks that are not publicly traded) approximates their fair value, determined primarily by analysis of company financial statements and recent capital issuances of the respective companies or banks, if any, and represents a Level 3 measurement. Loans held for sale: The fair value estimation process for the loans held for sale portfolio is segregated by loan type. The estimated fair value was based on what secondary markets are currently offering for portfolios with similar characteristics and represents a Level 2 measurement. Loans, net : For variable-rate loans that reprice frequently and with no significant change in credit risk or other optionality, fair values are based on carrying values. Fair values for all other loans are estimated by discounting contractual cash flows using estimated market discount rates, which reflect the credit and interest rate risk inherent in the loan. Collateral-dependent and impaired loans are included in loans, net. The fair value of loans is considered to be a Level 3 measurement due to internally developed discounted cash flow measurements. Deposits : The fair value of deposits with no stated maturity (such as demand deposits, savings, interest and noninterest checking, and money market accounts) is, by definition, equal to the amount payable on demand at the reporting date. Fair values for fixed-rate certificates of deposit are estimated using a discounted cash flow calculation that applies interest rates currently being offered in the market place on certificates of similar remaining maturities. Use of internal discounted cash flows provides a Level 3 fair value measurement. Long-term borrowings : The fair value of the FHLB advances is obtained from the FHLB which uses a discounted cash flow analysis based on current market rates of similar maturity debt securities and represents a Level 2 measurement. The fair values of the junior subordinated debentures and subordinated notes utilize a discounted cash flow analysis based on an estimate of current interest rates being offered by instruments with similar terms and credit quality. Since the market for these instruments is limited, the internal valuation represents a Level 3 measurement. Lending-related commitments : At December 31, 2020 and 2019, the estimated fair value of letters of credit, interest rate lock commitments on residential mortgage loans, outstanding mandatory commitments to sell residential mortgage loans into the secondary market, and mirror interest rate swap agreements were not significant. Limitations : Fair value estimates are made at a specific point in time, based on relevant market information and information about the financial instrument. These estimates do not reflect any premium or discount that could result from offering for sale at one time the Company’s entire holdings of a particular financial instrument. Fair value estimates may not be realizable in an immediate settlement of the instrument. In some instances, there are no quoted market prices for the Company’s various financial instruments, in which case fair values may be based on estimates using present value or other valuation techniques, or based on judgments regarding future expected loss experience, current economic conditions, risk characteristics of the financial instruments, or other factors. Those techniques are significantly affected by the assumptions used, including the discount rate and estimate of future cash flows. Subsequent changes in assumptions could significantly affect the estimates.

PARENT COMPANY ONLY FINANCIAL I

PARENT COMPANY ONLY FINANCIAL INFORMATION	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
PARENT COMPANY ONLY FINANCIAL INFORMATION	PARENT COMPANY ONLY FINANCIAL INFORMATION Condensed Parent Company only financial statements of Nicolet Bankshares, Inc. follow. Balance Sheets December 31, (in thousands) 2020 2019 Assets Cash and due from subsidiary $ 49,998 $ 70,426 Investments 6,742 6,650 Investments in subsidiaries 513,736 487,644 Goodwill (3,266) (3,266) Other assets 177 396 Total assets $ 567,387 $ 561,850 Liabilities and Stockholders’ Equity Junior subordinated debentures $ 24,869 $ 30,575 Subordinated notes — 11,993 Other liabilities 3,329 3,020 Stockholders’ equity 539,189 516,262 Total liabilities and stockholders’ equity $ 567,387 $ 561,850 Statements of Income Years Ended December 31, (in thousands) 2020 2019 2018 Interest income $ 39 $ 55 $ 52 Interest expense 2,313 2,936 2,844 Net interest expense (2,274) (2,881) (2,792) Dividend income from subsidiaries 60,215 50,363 40,775 Operating expense (886) (321) (364) Gain (loss) on investments, net (1,087) 1,015 265 Income tax benefit 1,102 506 305 Earnings before equity in undistributed income (loss) of subsidiaries 57,070 48,682 38,189 Equity in undistributed income (loss) of subsidiaries 3,052 5,959 2,847 Net income attributable to Nicolet Bankshares, Inc. $ 60,122 $ 54,641 $ 41,036 Statements of Cash Flows Years Ended December 31, (in thousands) 2020 2019 2018 Cash Flows From Operating Activities: Net income attributable to Nicolet Bankshares, Inc. $ 60,122 $ 54,641 $ 41,036 Adjustments to reconcile net income to net cash provided by operating activities: Accretion of discounts 486 515 515 (Gain) loss on investments, net 1,087 (1,015) (265) Change in other assets and liabilities, net 1,786 (421) (25) Equity in undistributed (income) loss of subsidiaries, net of dividends (3,052) (5,959) (2,847) Net cash provided by operating activities 60,429 47,761 38,414 Cash Flows from Investing Activities: Proceeds from sale of investments 185 — 708 Purchases of investments (1,179) (2,484) (920) Net cash paid in business combinations (21,644) (412) — Net cash used in investing activities (22,638) (2,896) (212) Cash Flows From Financing Activities: Purchase and retirement of common stock (42,088) (28,460) (22,749) Proceeds from issuance of common stock, net 2,055 8,742 1,800 Repayment of long-term borrowings (18,186) — — Net cash used in financing activities (58,219) (19,718) (20,949) Net increase (decrease) in cash and due from subsidiary (20,428) 25,147 17,253 Beginning cash and due from subsidiary 70,426 45,279 28,026 Ending cash and due from subsidiary $ 49,998 $ 70,426 $ 45,279

EARNINGS PER COMMON SHARE

EARNINGS PER COMMON SHARE	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
EARNINGS PER COMMON SHARE	EARNINGS PER COMMON SHARE See Note 1 for the Company’s accounting policy on earnings per common share. Presented below are the calculations for basic and diluted earnings per common share. Years Ended December 31, (in thousands, except per share data) 2020 2019 2018 Net income attributable to Nicolet Bankshares, Inc. $ 60,122 $ 54,641 $ 41,036 Weighted average common shares outstanding 10,337 9,562 9,640 Effect of dilutive common stock awards 204 338 316 Diluted weighted average common shares outstanding 10,541 9,900 9,956 Basic earnings per common share $ 5.82 $ 5.71 $ 4.26 Diluted earnings per common share $ 5.70 $ 5.52 $ 4.12 Options to purchase 0.1 million shares for the year ended December 31, 2020 were excluded from the calculation of diluted earnings per common share as the effect of their exercise would have been anti-dilutive. Options to purchase less than 0.1 million shares outstanding for year ended December 31, 2019 and options to purchase 0.1 million shares outstanding for the year ended December 31, 2018, respectively, were excluded from the calculation of diluted earnings per share as the effect of their exercise would have been anti-dilutive.

REVENUE RECOGNITION

REVENUE RECOGNITION	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION See Note 1 for the Company’s accounting policy on revenue recognition in accordance with Topic 606. This guidance does not apply to revenue associated with financial instruments, including revenue from loans and securities. In addition, certain noninterest income categories such as gains or losses associated with mortgage servicing rights, derivatives, and income from BOLI are not within the scope of the new guidance. The main types of revenue contracts within the scope of Topic 606 include trust services fee income, brokerage fee income, service charges on deposit accounts, card interchange income, and certain other noninterest income. These contracts are discussed in detail below: Trust services and brokerage fee income : A contract between the Company and its customers to provide fiduciary and / or investment administration services on trust accounts and brokerage accounts in exchange for a fee. Trust services and brokerage fee income is generally based upon the month-end market value of the assets under management and the applicable fee rate, which is recognized over the period the underlying trust or brokerage account is serviced (generally on a monthly basis). Such contracts are generally cancellable at any time, with the customer subject to a pro-rated fee in the month of termination. Service charges on deposit accounts : The deposit contract obligates the Company to serve as a custodian of the customer’s deposited funds and generally can be terminated at will by either party. This contract permits the customer to access the funds on deposit and request additional services related to the deposit account. Service charges on deposit accounts consist of account analysis fees (net fees earned on analyzed business and public checking accounts), monthly service charges, nonsufficient fund (“NSF”) charges, and other deposit account related charges. The Company’s performance obligation for account analysis fees and monthly service charges is generally satisfied, and the related revenue recognized, over the period in which the service is provided (typically on a monthly basis); while NSF charges and other deposit account related charges are largely transactional based and the related revenue is recognized at the time the service is provided. Card interchange income : A contract between the Company, as a card-issuing bank, and its customers whereby the Company receives a transaction fee from the merchant’s bank whenever a customer uses a debit or credit card to make a purchase. The performance obligation is completed and the fees are recognized as the service is provided (i.e., when the customer uses a debit or credit card). Other noninterest income : Other noninterest income includes several items, such as wire transfer income, check cashing fees, check printing fees, safe deposit box rental fees, management fee income, and consulting fees. These fees are generally recognized at the time the service is provided.

NATURE OF BUSINESS AND SIGNIF_2

NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation : The consolidated financial statements of the Company include the accounts of its subsidiaries. The JV underlies the noncontrolling interest reflected in the consolidated financial statements until late 2020 when the Bank purchased the remaining interest as discussed in Note 1 above under Nature of Banking Activities and Subsidiaries. The consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and conform to general practices within the banking industry. All significant intercompany accounts and transactions have been eliminated in the consolidated financial statements. Results of operations of companies purchased, if any, are included from the date of acquisition.
Operating Segment	Operating Segment : The consolidated income of the Company is derived principally from the Bank, which conducts lending (primarily commercial-based loans, as well as residential and consumer loans) and deposit gathering (including other banking- and deposit-related products and services, such as ATMs, safe deposit boxes, check cashing, wires, and debit cards) to businesses, consumers and governmental units principally in its trade area of northeastern and central Wisconsin, and Menominee, Michigan, trust services, brokerage services (delivered through the Bank and Nicolet Advisory), and the support to deliver, fund and manage all such banking and wealth management services to its customer base. The individual contribution from wealth management was not significant to the consolidated balance sheet or net income for 2020, 2019, or 2018. While the chief operating decision makers monitor the revenue streams of the various products and services, and evaluate costs, balance sheet positions and quality, all such products, services and activities are directly or indirectly related to the business of community banking, with no regular, formal or material segment delineations. Operations are managed and financial performance is evaluated on a company-wide basis, and accordingly, all the financial service operations are considered by management to be aggregated in one reportable operating segment.
Use of Estimates	Use of 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, 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-loans, 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.
Business Combinations	Business Combinations : The Company accounts for business combinations under the acquisition method of accounting in accordance with Accounting Standards Codification (“ASC”) 805, Business Combinations
Cash and Cash Equivalents	Cash and Cash Equivalents: For purposes of the consolidated statements of cash flows, cash and cash equivalents include cash and due from banks, interest-earning deposits in other banks with original maturities of less than 90 days, if any, and federal funds sold. The Bank maintains amounts in due from banks which, at times, may exceed federally insured limits. Management monitors these correspondent relationships. The Bank has not experienced any losses in such accounts. The Bank may have restrictions on cash and due from banks as it is required to maintain certain vault cash and reserve balances with the Federal Reserve Bank to meet specific reserve requirements.
Securities Available for Sale	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. Securities classified as AFS are carried at fair value, with unrealized gains or losses, net of related deferred income taxes, reported as increases or decreases in accumulated other comprehensive income. Realized gains or losses on sales of securities AFS (using the specific identification method) are included in the consolidated statements of income under asset gains (losses), net. Premiums and discounts are amortized or accreted into interest income over the estimated life of the related securities using the effective interest method.
Other Investments	Other Investments: Other investments include equity securities with readily determinable fair values, “restricted” equity securities, and private company securities. At December 31, 2020, other investments included $3.6 million of equity securities with readily determinable fair values, $20.2 million of “restricted“ equity securities, and $3.9 million of private company securities. As a member of the Federal Reserve Bank System and the Federal Home Loan Bank (“FHLB”) System, the Bank is required to maintain an investment in the capital stock of these entities. These equity securities are “restricted” in that they can only be sold back to the respective institutions or another member institution at par. Therefore, they are less liquid than other exchange traded equity securities. As no ready market exists for these stocks, and they have no quoted market value, these investments are carried at cost. Also included are investments in other private companies that do not have quoted market prices, which are carried at cost less impairment charges, if any. Management’s evaluation of these other investments for impairment includes consideration of the financial condition and other available relevant information of the issuer.
Loans Held for Sale	Loans Held for Sale : Loans originated and intended for sale in the secondary market are carried at the lower of cost or estimated fair value as determined on an aggregate basis and generally consist of current production of certain fixed-rate residential first mortgages. The amount by which cost exceeds fair value is recorded as a valuation allowance and charged to earnings. Changes, if any, in the valuation allowance are included in earnings in the period in which the change occurs. As of December 31, 2020 and 2019, no valuation allowance was necessary. Loans held for sale may be sold servicing retained or servicing released, and are generally sold without recourse. The carrying value of mortgage loans sold with servicing retained is reduced by the amount allocated to the servicing right at the time of sale. Gains and losses on sales of mortgage loans held for sale are included in earnings in mortgage income, net.
Loans - Originated and Acquired	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 amount outstanding, net of deferred loan fees and costs, and any direct principal charge-off. 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 4 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 on the acquisition date. 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 4 for additional information and disclosures on loans.
Allowance for Credit Losses	Management evaluates securities AFS in unrealized loss positions on a quarterly basis to determine whether the decline in fair value below the amortized cost 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 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 must be recognized in net income with a corresponding adjustment to the security’s amortized cost basis rather than through the establishment on an ACL. See Note 3 for additional disclosures on AFS securities. Allowance for Credit Losses - Loans : The ACL-Loans represents management’s estimate of expected credit losses over the lifetime of the loan based on loans 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. Actual credit losses, net of recoveries, are deducted from the ACL-Loans. Loans are charged-off when management believes that the collectability of the principal is unlikely. Subsequent recoveries, if any, are credited to the ACL-Loans. A provision for credit losses, which is a charge against income, is recorded to bring the ACL-Loans to a level that, in management’s judgment, is appropriate to absorb expected credit losses in the loan portfolio. Prior to January 1, 2020, the Company used an incurred loss impairment model to estimate the ACL-Loans. 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. Effective January 1, 2020, the Company uses a current expected credit loss model (“CECL”) to estimate the ACL-Loans. 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 and other credit-deteriorated 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. To assess the overall appropriateness of the ACL-Loans, management applies an allocation methodology which focuses on evaluation of qualitative and environmental factors, including but not limited to: (i) evaluation of facts and issues related to specific loans; (ii) management's ongoing review and grading of the loan portfolio; (iii) consideration of historical loan loss and delinquency experience on each portfolio segment; (iv) trends in past due and nonaccrual loans; (v) the risk characteristics of the various loan segments; (vi) changes in the size and character of the loan portfolio; (vii) concentrations of loans to specific borrowers or industries; (viii) existing economic conditions; (ix) the fair value of underlying collateral; and (x) other qualitative and quantitative factors which could affect expected credit losses. Assessing these numerous factors involves significant judgment. Management allocates the ACL-Loans by pools of risk within each loan portfolio segment. The allocation methodology consists of the following components. First, a specific reserve is established for individually evaluated PCD and other credit-deteriorated loans, which management defines as nonaccrual credit relationships over $250,000, collateral dependent loans, and other loans with evidence of credit deterioration. The specific reserve in the ACL-Loans for these credit deteriorated loans is equal to the aggregate collateral or discounted cash flow shortfall. Management allocates the ACL-Loans with historical loss rates by loan segment. The loss factors are measured on a quarterly basis and applied to each loan segment based on current loan balances and projected for their expected remaining life. Next, management allocates the ACL-Loans using the qualitative and environmental factors mentioned above. Consideration is given to those current qualitative or environmental factors that are likely to cause estimated credit losses at the evaluation date to differ from the historical loss experience of each loan segment. Lastly, management considers reasonable and supportable forecasts to assess the collectability of future cash flows. See Note 4 for additional information and disclosures on the ACL-Loans. Allocations to the ACL-Loans may be made for specific loans but the entire ACL-Loans is available for any loan that, in management’s judgment, should be charged-off or for which an actual loss is realized. The allowance analysis is reviewed by the Board on a quarterly basis in compliance with internal and regulatory requirements.
Credit-Related Financial Instruments	Credit-Related Financial Instruments : In the ordinary course of business the Company has entered into financial instruments consisting of commitments to extend credit, financial standby letters of credit, and performance standby letters of credit. Financial standby letters of credit are issued specifically to facilitate commerce and typically result in the commitment being drawn on when the underlying transaction is consummated between the customer and the third party, while performance standby letters of credit generally are contingent upon the failure of the customer to perform according to the terms of the underlying contract with the third
Transfers of Financial Assets	Transfers of Financial Assets : Transfers of financial assets, primarily in loan participation activities, are accounted for as sales only when control over the assets has been surrendered. Control over transferred assets is deemed to be surrendered when (1) the assets have been isolated from the Company, (2) the transferee obtains the right (free of conditions that constrain it from taking advantage of the right) to pledge or exchange the transferred assets, and (3) the Company does not maintain effective control over the transferred assets through an agreement to repurchase them before their maturity or the ability to unilaterally cause the holder to return assets.
Premises and Equipment	Premises and Equipment : Premises and equipment are stated at cost less accumulated depreciation and amortization. Premises and equipment from acquisitions were recorded at estimated fair value on the respective dates of acquisition. Depreciation is computed on a straight-line basis over the estimated useful lives of the related assets. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the improvements or the terms of the related leases. Maintenance and repairs are expensed as incurred. See Note 5 for additional information on premises and equipment. Estimated useful lives of new premises and equipment generally range as follows: Building and improvements 25 – 40 years Leasehold improvements 5 – 15 years Furniture and equipment 3 – 10 years
Operating Leases	Operating Leases : The Company accounts for its operating leases in accordance with ASC 842, Leases (“ASC 842”), which requires lessees to record almost all leases on the balance sheet as a right-of-use (“ROU”) asset and lease liability. The operating lease ROU asset represents the right to use an underlying asset during the lease term (included in accrued interest receivable and other assets on the consolidated balance sheets), while the operating lease liability represents the obligation to make lease payments arising from the lease (included in accrued interest payable and other liabilities
Other Real Estate Owned ("OREO")	Other Real Estate Owned (“OREO”): OREO acquired through partial or total satisfaction of loans or bank facilities no longer in use are carried at fair value less estimated costs to sell. Any write-down in the carrying value of loans or vacated bank premises at the time of transfer to OREO is charged to the ACL-Loans or to write-down of assets, respectively. OREO properties acquired in conjunction with acquisition transactions were recorded at fair value on the date of acquisition. Any subsequent write-downs to reflect current fair value, as well as gains or losses on disposition and revenues and expenses incurred to hold and maintain such properties, are treated as period costs. At December 31, 2020 and 2019, OREO was $3.6 million and $1.0 million, respectively.
Goodwill and Other Intangibles	Goodwill and Other Intangibles : Goodwill represents the excess of the purchase price over the fair value of the net identifiable assets acquired. Goodwill is not amortized but, instead, is subject to impairment tests on at least an annual basis or more frequently if certain events or circumstances occur. Other intangibles include core deposit intangibles (which represent the value of acquired customer core deposit bases) and customer list intangibles. The core deposit intangibles have an estimated finite life, are amortized on an accelerated basis over a 10-year period, and are subject to periodic impairment evaluation. The customer list intangibles have finite lives, are amortized on a straight-line basis to expense over their initial weighted average life of approximately 12 years as of acquisition, and are subject to periodic impairment evaluation. See Note 6 for additional information on goodwill and other intangibles.
Mortgage Servicing Rights ("MSRs")	Mortgage Servicing Rights (“MSRs”) : The Company sells originated residential mortgages into the secondary market and retains the right to service the loans sold. A mortgage servicing right asset (liability) is capitalized upon sale of such loans with the offsetting effect recorded as a gain (loss) on sale of loan in earnings (included in mortgage income, net), representing the then-current estimated fair value of future net cash flows expected to be realized for performing the servicing activities. MSRs when purchased (including MSRs purchased in acquisitions) are initially recorded at their then-estimated fair value. As the Company has not elected to measure any class of servicing assets under the fair value method, the Company utilizes the amortization method. MSRs are amortized in proportion to and over the period of estimated net servicing income, with the amortization charged to earnings (included in mortgage income, net). MSRs are carried at the lower of initial capitalized amount, net of accumulated amortization, or estimated fair value, and are included in other assets in the consolidated balance sheets. Loan servicing fee income for servicing loans is typically based on a contractual percentage of the outstanding principal and is recorded as income when earned (included in mortgage income, net with less material late fees and ancillary fees related to loan servicing).
Bank-owned Life Insurance ("BOLI")	Bank-owned Life Insurance (“BOLI”) : The Company owns BOLI on certain executives and employees. BOLI balances are recorded at their cash surrender values. Changes in the cash surrender values and death proceeds exceeding carrying values are included in BOLI income.
Short-term Borrowings	Short-term Borrowings: Short-term borrowings consist primarily of overnight Federal funds purchased and securities sold under agreements to repurchase (“repos”), or other short-term borrowing arrangements with an original maturity of one year or less. Repos are with commercial deposit customers, and are treated as financing activities carried at the amounts that will be subsequently repurchased as specified in the respective agreements. Repos generally mature within one
Stock-based Compensation Plans	Stock-based Compensation :
Income Taxes	Income Taxes : The Company files a consolidated federal income tax return and a combined state income tax return (both of which include the Company and its wholly owned subsidiaries). Accordingly, amounts equal to tax benefits of those companies having taxable federal losses or credits are reimbursed by the companies that incur federal tax liabilities. Amounts provided for income tax expense are based on income reported for financial statement purposes and do not necessarily represent amounts currently payable under tax laws. Deferred income tax assets and liabilities are computed quarterly for differences between the financial statement and tax bases of assets and liabilities that will result in taxable or deductible amounts in the future based on enacted tax rates applicable to the periods in which the differences are expected to affect taxable income. As changes in tax laws or rates are enacted, deferred tax assets and liabilities are adjusted through income tax expense. Valuation allowances are established when it is more likely than not that a portion of the full amount of the deferred tax asset will not be realized. In assessing the ability to realize deferred tax assets, management considers the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies.
Earnings per Common Share	Earnings per Common Share : Basic earnings per common share are calculated by dividing net income available to common shareholders by the weighted average number of common shares outstanding during the period. Diluted earnings per common share are calculated by dividing net income available to common shareholders by the weighted average number of common shares adjusted for the dilutive effect of outstanding common stock awards, if any. See Note 19 for additional information on earnings per common share.
Treasury Stock	Treasury Stock : Treasury stock is accounted for at cost on a first-in-first-out basis. It is the Company’s general practice to cancel treasury stock shares in the same quarter as purchased, and thus, not carry a treasury stock balance.
Comprehensive Income	Comprehensive Income : Accounting principles generally require that recognized revenue, expenses, gains and losses be included in net income. Certain changes in assets and liabilities, such as unrealized gains and losses on securities AFS, are reported in accumulated other comprehensive income, as a separate component of the equity section of the balance sheet. Realized gains or losses are reclassified to current period income. Changes in these items, along with net income, are components of comprehensive income. The Company presents comprehensive income in a separate consolidated statement of comprehensive income.
Revenue Recognition	Revenue Recognition : Accounting principles ( Revenue from Contracts with Customers, Topic 606)
Reclassifications	Reclassifications : Certain amounts in the 2019 and 2018 consolidated financial statements have been reclassified to conform to the 2020 presentation.
New Accounting Pronouncements Adopted	New Accounting Pronouncements 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 17 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 replaced the incurred loss impairment model (which recognized losses when a probable threshold was 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 Securities Available for Sale, Loans, and Allowance for Credit Losses above for changes to accounting policies and see Notes 3 and 4 for additional disclosures related to this new accounting pronouncement.

NATURE OF BUSINESS AND SIGNIF_3

NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Schedule of estimated useful lives of premises and equipment	Estimated useful lives of new premises and equipment generally range as follows: Building and improvements 25 – 40 years Leasehold improvements 5 – 15 years Furniture and equipment 3 – 10 years

SECURITIES AVAILABLE FOR SALE (

SECURITIES AVAILABLE FOR SALE (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Securities, Available-for-sale [Abstract]
Schedule of amortized costs and fair values of securities AFS	Amortized cost and fair value of securities available for sale are summarized as follows. December 31, 2020 (in thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Fair Fair Value as % of Total U.S. government agency securities $ 63,162 $ 289 $ — $ 63,451 12 % State, county and municipals 226,493 5,386 11 231,868 43 % Mortgage-backed securities 156,148 6,425 78 162,495 30 % Corporate debt securities 76,073 5,450 — 81,523 15 % $ 521,876 $ 17,550 $ 89 $ 539,337 100 % December 31, 2019 (in thousands) Amortized Gross Unrealized Gains Gross Unrealized Losses Fair Fair Value as % of Total U.S. government agency securities $ 16,516 $ 4 $ 60 $ 16,460 4 % State, county and municipals 155,501 1,049 157 156,393 35 % Mortgage-backed securities 193,223 2,492 697 195,018 43 % Corporate debt securities 78,009 3,422 — 81,431 18 % $ 443,249 $ 6,967 $ 914 $ 449,302 100 %
Schedule of gross unrealized losses on securities AFS	The following tables present gross unrealized losses and the related estimated fair value of investment securities AFS for which an allowance for credit losses has not been recorded, aggregated by investment category and the length of time the individual securities have been in a continuous unrealized loss position. December 31, 2020 Less than 12 months 12 months or more Total ($ in thousands) Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Number of Securities State, county and municipals $ 5,181 $ 11 $ — $ — $ 5,181 $ 11 9 Mortgage-backed securities 10,612 71 492 7 11,104 78 22 $ 15,793 $ 82 $ 492 $ 7 $ 16,285 $ 89 31 December 31, 2019 Less than 12 months 12 months or more Total ($ in thousands) Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Number of Securities U.S. government agency securities $ 1,035 $ 2 $ 11,091 $ 58 $ 12,126 $ 60 6 State, county and municipals 22,451 132 7,605 25 30,056 157 56 Mortgage-backed securities 49,626 245 47,271 452 96,897 697 150 $ 73,112 $ 379 $ 65,967 $ 535 $ 139,079 $ 914 212
Schedule of amortized cost and fair value classified by contractual maturities	The amortized cost and fair value of securities AFS by contractual maturity are shown below. Expected maturities may differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without call or prepayment penalties; as this is particularly inherent in mortgage-backed securities, these securities are not included in the maturity categories below. See Note 17 for additional information on the Company’s fair value measurements. December 31, 2020 (in thousands) Amortized Cost Fair Value Due in less than one year $ 85,317 $ 85,712 Due in one year through five years 168,302 174,975 Due after five years through ten years 97,662 100,445 Due after ten years 14,447 15,710 365,728 376,842 Mortgage-backed securities 156,148 162,495 Securities AFS $ 521,876 $ 539,337
Schedule of proceeds and realized gains / losses from sales of securities AFS	Proceeds and realized gains / losses from the sale of securities AFS were as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Gross gains $ 395 $ 152 $ — Gross losses — (174) (212) Gains (losses) on sales of securities AFS, net $ 395 $ (22) $ (212) Proceeds from sales of securities AFS $ 19,045 $ 23,405 $ 5,280

LOANS, ALLOWANCE FOR CREDIT LOS

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY (Tables)	12 Months Ended
	Dec. 31, 2020
Receivables [Abstract]
Schedule of loan composition by portfolio segment	The loan composition was as follows. December 31, 2020 December 31, 2019 (in thousands) Amount % of Total Amount % of Total Commercial & industrial $ 750,718 27 % $ 806,189 31 % Paycheck Protection Program (“PPP”) loans 186,016 7 — — Owner-occupied commercial real estate (“CRE”) 521,300 19 496,372 19 Agricultural 109,629 4 95,450 4 CRE investment 460,721 16 443,218 17 Construction & land development 131,283 5 92,970 4 Residential construction 41,707 1 54,403 2 Residential first mortgage 444,155 16 432,167 17 Residential junior mortgage 111,877 4 122,771 5 Retail & other 31,695 1 30,211 1 Loans 2,789,101 100 % 2,573,751 100 % Less ACL-Loans 32,173 13,972 Loans, net $ 2,756,928 $ 2,559,779 ACL-Loans to loans 1.15 % 0.54 %
Schedule of changes in the allowance for credit losses - loans by portfolio segment	A roll forward of the allowance for credit losses - loans was as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Beginning balance $ 13,972 $ 13,153 $ 12,653 Adoption of CECL 8,488 — — Initial PCD ACL 797 — — Total impact for adoption of CECL 9,285 — — Provision for credit losses 10,300 1,200 1,600 Charge-offs (1,689) (927) (1,213) Recoveries 305 546 113 Net (charge-offs) recoveries (1,384) (381) (1,100) Ending balance $ 32,173 $ 13,972 $ 13,153 The following table presents the balance and activity in the ACL-Loans by portfolio segment. Year Ended December 31, 2020 (in thousands) Commercial Owner- Agricultural CRE Construction & land Residential Residential Residential Retail Total ACL-Loans * Beginning balance $ 5,471 $ 3,010 $ 579 $ 1,600 $ 414 $ 368 $ 1,669 $ 517 $ 344 $ 13,972 Adoption of CECL 2,962 1,249 361 1,970 51 124 1,286 351 134 8,488 Initial PCD ACL 797 — — — — — — — — 797 Provision 3,106 2,062 455 2,061 519 (71) 1,809 151 208 10,300 Charge-offs (812) (530) — (190) — — (2) — (155) (1,689) Recoveries 120 81 — — — — 11 67 26 305 Net (charge-offs) recoveries (692) (449) — (190) — — 9 67 (129) (1,384) Ending balance $ 11,644 $ 5,872 $ 1,395 $ 5,441 $ 984 $ 421 $ 4,773 $ 1,086 $ 557 $ 32,173 As % of ACL-Loans 36 % 18 % 4 % 17 % 3 % 1 % 15 % 4 % 2 % 100 % * The PPP loans are fully guaranteed by the SBA; thus, no ACL-Loans has been allocated to these loans. For comparison purposes, the following table presents the balance and activity in the ACL-Loans by portfolio segment for the prior year-end period. Year Ended December 31, 2019 (in thousands) Commercial Owner- Agricultural CRE Construction & land Residential Residential Residential Retail Total ACL-Loans Beginning balance $ 5,271 $ 2,847 $ 422 $ 1,470 $ 510 $ 211 $ 1,646 $ 472 $ 304 $ 13,153 Provision (61) 254 157 130 (96) 383 9 86 338 1,200 Charge-offs (159) (93) — — — (226) (22) (80) (347) (927) Recoveries 420 2 — — — — 36 39 49 546 Net (charge-offs) recoveries 261 (91) — — — (226) 14 (41) (298) (381) Ending balance $ 5,471 $ 3,010 $ 579 $ 1,600 $ 414 $ 368 $ 1,669 $ 517 $ 344 $ 13,972 As % of ACL-Loans 39 % 22 % 4 % 11 % 3 % 3 % 12 % 4 % 2 % 100 %
Schedule of collateral dependent loans by portfolio segment	The following table presents collateral dependent loans by portfolio segment and collateral type, including those loans with and without a related allowance allocation as of December 31, 2020. December 31, 2020 Collateral Type (in thousands) Real Estate Other Business Assets Total Without an Allowance With an Allowance Allowance Allocation Commercial & industrial $ — $ 2,195 $ 2,195 $ 501 $ 1,694 $ 1,241 PPP loans — — — — — — Owner-occupied CRE 3,519 — 3,519 3,519 — — Agricultural 584 797 1,381 1,378 3 3 CRE investment 1,474 — 1,474 1,474 — — Construction & land development 308 — 308 308 — — Residential construction — — — — — — Residential first mortgage — — — — — — Residential junior mortgage — — — — — — Retail & other — — — — — — Total loans $ 5,885 $ 2,992 $ 8,877 $ 7,180 $ 1,697 $ 1,244
Schedule of impaired loans by portfolio segment	The following table presents impaired loans and their respective allowance for credit loss allocations at December 31, 2019, as determined in accordance with historical accounting guidance. December 31, 2019 (in thousands) Recorded Unpaid Principal Related Average Interest Income Commercial & industrial $ 5,932 $ 7,950 $ 625 $ 5,405 $ 1,170 Owner-occupied CRE 3,430 4,016 — 3,677 256 Agricultural 2,134 2,172 116 2,311 37 CRE investment 2,426 2,790 — 2,497 364 Construction & land development 382 382 — 460 — Residential construction — — — — — Residential first mortgage 2,357 2,629 — 2,412 178 Residential junior mortgage 218 349 — 224 58 Retail & other 12 12 — 12 — Total $ 16,891 $ 20,300 $ 741 $ 16,998 $ 2,063
Schedule of past due loans by portfolio segment	The following tables present past due loans by portfolio segment. December 31, 2020 (in thousands) 30-89 Days Past 90 Days & Over Current Total Commercial & industrial $ — $ 2,646 $ 748,072 $ 750,718 PPP loans — — 186,016 186,016 Owner-occupied CRE — 1,869 519,431 521,300 Agricultural 7 1,830 107,792 109,629 CRE investment — 1,488 459,233 460,721 Construction & land development — 327 130,956 131,283 Residential construction — — 41,707 41,707 Residential first mortgage 613 823 442,719 444,155 Residential junior mortgage 43 384 111,450 111,877 Retail & other 102 88 31,505 31,695 Total loans $ 765 $ 9,455 $ 2,778,881 $ 2,789,101 Percent of total loans — % 0.4 % 99.6 % 100.0 % December 31, 2019 (in thousands) 30-89 Days Past 90 Days & Over Current Total Commercial & industrial $ 1,729 $ 6,249 $ 798,211 $ 806,189 Owner-occupied CRE 112 3,311 492,949 496,372 Agricultural — 1,898 93,552 95,450 CRE investment — 1,073 442,145 443,218 Construction & land development 2,063 20 90,887 92,970 Residential construction 302 — 54,101 54,403 Residential first mortgage 2,736 1,090 428,341 432,167 Residential junior mortgage 217 480 122,074 122,771 Retail & other 110 1 30,100 30,211 Total loans $ 7,269 $ 14,122 $ 2,552,360 $ 2,573,751 Percent of total loans 0.3 % 0.5 % 99.2 % 100.0 %
Schedule of nonaccrual loans by portfolio segment	The following table presents nonaccrual loans by portfolio segment. The nonaccrual loans without a related allowance for credit losses have been reflected in the collateral dependent loans table above. Total Nonaccrual Loans (in thousands) December 31, 2020 % to Total December 31, 2019 % to Total Commercial & industrial $ 2,646 28 % $ 6,249 44 % PPP loans — — — — Owner-occupied CRE 1,869 20 3,311 23 Agricultural 1,830 19 1,898 14 CRE investment 1,488 16 1,073 8 Construction & land development 327 3 20 — Residential construction — — — — Residential first mortgage 823 9 1,090 8 Residential junior mortgage 384 4 480 3 Retail & other 88 1 1 — Nonaccrual loans $ 9,455 100 % $ 14,122 100 % Percent of total loans 0.4 % 0.5 %
Schedule of total loans by risk categories and year of origination	The following table presents total loans by risk categories and year of origination. December 31, 2020 Amortized Cost Basis by Origination Year (in thousands) 2020 2019 2018 2017 2016 Prior Revolving Revolving to Term TOTAL Commercial & industrial (a) Grades 1-4 $ 348,274 $ 121,989 $ 98,920 $ 72,027 $ 21,613 $ 39,454 $ 183,858 $ — $ 886,135 Grade 5 1,416 2,239 4,486 527 1,638 4,151 18,994 — 33,451 Grade 6 69 19 735 5,315 29 32 1,923 — 8,122 Grade 7 334 1,126 1,389 663 122 3,103 2,289 — 9,026 Total $ 350,093 $ 125,373 $ 105,530 $ 78,532 $ 23,402 $ 46,740 $ 207,064 $ — $ 936,734 Owner-occupied CRE Grades 1-4 $ 90,702 $ 74,029 $ 78,013 $ 52,911 $ 45,042 $ 150,624 $ 870 $ — $ 492,191 Grade 5 42 623 1,349 7,541 1,102 5,842 — — 16,499 Grade 6 — — — 1,710 — 706 — — 2,416 Grade 7 2,987 675 176 835 — 5,521 — — 10,194 Total $ 93,731 $ 75,327 $ 79,538 $ 62,997 $ 46,144 $ 162,693 $ 870 $ — $ 521,300 Agricultural Grades 1-4 $ 13,719 $ 5,652 $ 7,580 $ 9,745 $ 2,613 $ 32,702 $ 21,513 $ — $ 93,524 Grade 5 1,034 — 701 169 644 6,131 356 — 9,035 Grade 6 — — — 329 390 — — — 719 Grade 7 — — 26 110 1,111 5,042 62 — 6,351 Total $ 14,753 $ 5,652 $ 8,307 $ 10,353 $ 4,758 $ 43,875 $ 21,931 $ — $ 109,629 CRE investment Grades 1-4 $ 82,518 $ 78,841 $ 40,881 $ 69,643 $ 31,541 $ 137,048 $ 5,255 $ — $ 445,727 Grade 5 — — 47 1,284 1,828 9,073 — — 12,232 Grade 6 — — — 796 — — — — 796 Grade 7 — — — — — 1,966 — — 1,966 Total $ 82,518 $ 78,841 $ 40,928 $ 71,723 $ 33,369 $ 148,087 $ 5,255 $ — $ 460,721 Construction & land development Grades 1-4 $ 67,578 $ 30,733 $ 15,209 $ 2,204 $ 2,083 $ 7,266 $ 3,675 $ — $ 128,748 Grade 5 — 373 660 545 — 23 455 — 2,056 Grade 6 — — — — — — — — — Grade 7 — — — — — 479 — — 479 Total $ 67,578 $ 31,106 $ 15,869 $ 2,749 $ 2,083 $ 7,768 $ 4,130 $ — $ 131,283 Residential construction Grades 1-4 $ 31,687 $ 9,185 $ 395 $ 121 $ — $ 264 $ — $ — $ 41,652 Grade 5 — — — 55 — — — — 55 Grade 6 — — — — — — — — — Grade 7 — — — — — — — — — Total $ 31,687 $ 9,185 $ 395 $ 176 $ — $ 264 $ — $ — $ 41,707 Residential first mortgage Grades 1-4 $ 146,744 $ 64,013 $ 40,388 $ 41,245 $ 41,274 $ 103,094 $ 287 $ 5 $ 437,050 Grade 5 — 925 2,245 256 364 1,714 — — 5,504 Grade 6 — — — — — — — — — Grade 7 — 437 197 16 9 942 — — 1,601 Total $ 146,744 $ 65,375 $ 42,830 $ 41,517 $ 41,647 $ 105,750 $ 287 $ 5 $ 444,155 Residential junior mortgage Grades 1-4 $ 4,936 $ 4,338 $ 3,663 $ 1,060 $ 869 $ 3,131 $ 91,816 $ 1,648 $ 111,461 Grade 5 — — — — — 32 — — 32 Grade 6 — — — — — — — — — Grade 7 — — — 27 — 232 125 — 384 Total $ 4,936 $ 4,338 $ 3,663 $ 1,087 $ 869 $ 3,395 $ 91,941 $ 1,648 $ 111,877 Retail & other Grades 1-4 $ 8,083 $ 5,213 $ 1,942 $ 1,676 $ 752 $ 1,339 $ 12,602 $ — $ 31,607 Grade 5 — — — — — — — — — Grade 6 — — — — — — — — — Grade 7 16 — 22 — — 50 — — 88 Total $ 8,099 $ 5,213 $ 1,964 $ 1,676 $ 752 $ 1,389 $ 12,602 $ — $ 31,695 Total loans $ 800,139 $ 400,410 $ 299,024 $ 270,810 $ 153,024 $ 519,961 $ 344,080 $ 1,653 $ 2,789,101 (a) For purposes of this table, the $186 million net carrying value of PPP loans were originated in 2020, have a Pass risk grade (Grades 1-4) and have been included with the Commercial & industrial loan category. The following tables present total loans by risk categories. December 31, 2020 (in thousands) Grades 1-4 Grade 5 Grade 6 Grade 7 Total Commercial & industrial $ 700,119 $ 33,451 $ 8,122 $ 9,026 $ 750,718 PPP loans 186,016 — — — 186,016 Owner-occupied CRE 492,191 16,499 2,416 10,194 521,300 Agricultural 93,524 9,035 719 6,351 109,629 CRE investment 445,727 12,232 796 1,966 460,721 Construction & land development 128,748 2,056 — 479 131,283 Residential construction 41,652 55 — — 41,707 Residential first mortgage 437,050 5,504 — 1,601 444,155 Residential junior mortgage 111,461 32 — 384 111,877 Retail & other 31,607 — — 88 31,695 Total loans $ 2,668,095 $ 78,864 $ 12,053 $ 30,089 $ 2,789,101 Percent of total loans 95.7 % 2.8 % 0.4 % 1.1 % 100.0 % December 31, 2019 (in thousands) Grades 1-4 Grade 5 Grade 6 Grade 7 Total Commercial & industrial $ 765,073 $ 20,199 $ 7,663 $ 13,254 $ 806,189 Owner-occupied CRE 464,661 20,855 953 9,903 496,372 Agricultural 77,082 6,785 3,275 8,308 95,450 CRE investment 430,794 8,085 2,578 1,761 443,218 Construction & land development 90,523 2,213 15 219 92,970 Residential construction 53,286 1,117 — — 54,403 Residential first mortgage 424,044 4,677 668 2,778 432,167 Residential junior mortgage 122,249 35 — 487 122,771 Retail & other 30,210 — — 1 30,211 Total loans $ 2,457,922 $ 63,966 $ 15,152 $ 36,711 $ 2,573,751 Percent of total loans 95.5 % 2.5 % 0.6 % 1.4 % 100.0 %

PREMISES AND EQUIPMENT (Tables)

PREMISES AND EQUIPMENT (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of Premises and equipment, less accumulated depreciation and amortization	Premises and equipment, less accumulated depreciation and amortization, is summarized as follows. (in thousands) December 31, 2020 December 31, 2019 Land $ 6,344 $ 7,418 Land improvements 3,950 3,865 Building and improvements 54,989 50,818 Leasehold improvements 4,381 4,580 Furniture and equipment 22,701 20,262 92,365 86,943 Less accumulated depreciation and amortization 32,421 30,474 Premises and equipment, net $ 59,944 $ 56,469
Schedule of operating lease	A summary of net lease cost and selected other information related to operating leases was as follows. Years Ended ($ in thousands) December 31, 2020 December 31, 2019 Net lease cost: Operating lease cost $ 834 $ 970 Variable lease cost 169 233 Net lease cost $ 1,003 $ 1,203 Selected other operating lease information: Weighted average remaining lease term (years) 5.1 4.3 Weighted average discount rate 2.0 % 2.5 %
Schedule of maturity of remaining lease liabilities	The following table summarizes the maturity of remaining lease liabilities. Years Ending December 31, (in thousands) 2021 $ 920 2022 780 2023 497 2024 391 2025 106 Thereafter 507 Total future minimum lease payments 3,201 Less: amount representing interest (63) Present value of net future minimum lease payments $ 3,138

GOODWILL AND OTHER INTANGIBLE_2

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS (Tables)	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of goodwill and other intangibles	A summary of goodwill and other intangibles was as follows. (in thousands) December 31, 2020 December 31, 2019 Goodwill $ 163,151 $ 151,198 Core deposit intangibles 8,837 10,897 Customer list intangibles 3,365 3,872 Other intangibles 12,202 14,769 Goodwill and other intangibles, net $ 175,353 $ 165,967
Schedule of goodwill	(in thousands) December 31, 2020 December 31, 2019 Goodwill: Goodwill at beginning of year $ 151,198 $ 107,366 Acquisition 11,953 44,594 Impairment — (762) Goodwill at end of year $ 163,151 $ 151,198
Schedule of other intangibles	(in thousands) December 31, 2020 December 31, 2019 Core deposit intangibles: Gross carrying amount $ 31,715 $ 30,715 Accumulated amortization (22,878) (19,818) Net book value $ 8,837 $ 10,897 Additions during the period $ 1,000 $ 1,700 Amortization during the period $ 3,060 $ 3,365 Customer list intangibles: Gross carrying amount $ 5,523 $ 5,523 Accumulated amortization (2,158) (1,651) Net book value $ 3,365 $ 3,872 Amortization during the period $ 507 $ 507
Schedule of mortgage servicing rights	A summary of the changes in the MSR asset was as follows. (in thousands) December 31, 2020 December 31, 2019 MSR asset: MSR asset at beginning of year $ 5,919 $ 3,749 Capitalized MSR 5,256 2,876 MSR asset acquired 529 160 Amortization during the period (1,474) (866) MSR asset at end of year $ 10,230 $ 5,919 Valuation allowance at beginning of year $ — $ — Additions (1,000) — Valuation allowance at end of year $ (1,000) $ — MSR asset, net $ 9,230 $ 5,919 Fair value of MSR asset at end of period $ 9,276 $ 8,420 Residential mortgage loans serviced for others $ 1,250,206 $ 847,756 Net book value of MSR asset to loans serviced for others 0.74 % 0.70 %
Schedule of estimated future amortization expense for amortizing intangible assets and the MSR asset	The following table shows the estimated future amortization expense for amortizing intangible assets and the MSR asset. The projections are based on existing asset balances, the current interest rate environment and prepayment speeds as of December 31, 2020. The actual amortization expense the Company recognizes in any given period may be significantly different depending upon acquisition or sale activities, changes in interest rates, prepayment speeds, market conditions, regulatory requirements and events or circumstances that indicate the carrying amount of an asset may not be recoverable. (in thousands) Core deposit Customer list MSR asset Years Ending December 31, 2021 $ 2,643 $ 507 $ 1,771 2022 2,150 507 1,740 2023 1,633 483 1,635 2024 1,130 449 1,225 2025 670 449 876 Thereafter 611 970 2,983 Total $ 8,837 $ 3,365 $ 10,230

DEPOSITS (Tables)

DEPOSITS (Tables)	12 Months Ended
	Dec. 31, 2020
Deposits [Abstract]
Schedule of maturities of time deposits	At December 31, 2020, the scheduled maturities of time deposits were as follows. Years Ending December 31, (in thousands) 2021 $ 335,433 2022 118,898 2023 114,432 2024 37,169 2025 17,544 Thereafter 997 Total time deposits $ 624,473

SHORT AND LONG-TERM BORROWINGS

SHORT AND LONG-TERM BORROWINGS (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of long-term borrowings	The components of long-term borrowings (borrowing with an original contractual maturity greater than one year) were as follows. (in thousands) December 31, 2020 December 31, 2019 FHLB advances $ 29,000 $ 25,061 Junior subordinated debentures 24,869 30,575 Subordinated notes — 11,993 Total long-term borrowings $ 53,869 $ 67,629
Schedule of maturity of FHLB advances	The following table shows the maturity schedule of the FHLB advances as of December 31, 2020. Maturing in: (in thousands) 2021 $ 4,000 2022 — 2023 — 2024 — 2025 5,000 Thereafter 20,000 $ 29,000
Schedule of junior subordinated debentures	The following table shows the breakdown of junior subordinated debentures. Interest on all debentures is current. Any applicable discounts (initially recorded to carry an acquired debenture at its then estimated fair value) are being accreted to interest expense over the remaining life of the debentures. All the debentures below are currently callable and may be redeemed in part or in full, at par, plus any accrued but unpaid interest. On December 31, 2020, the Company redeemed in full its 2004 Nicolet Bankshares Statutory Trust junior subordinated debentures. Junior Subordinated Debentures (in thousands) Maturity Par 12/31/2020 Unamortized Discount 12/31/2020 Carrying Value 12/31/2019 Carrying Value 2004 Nicolet Bankshares Statutory Trust (1) 7/15/2034 $ — $ — $ — $ 6,186 2005 Mid-Wisconsin Financial Services, Inc. (2) 12/15/2035 10,310 (2,972) 7,338 7,138 2006 Baylake Corp. (3) 9/30/2036 16,598 (3,647) 12,951 12,715 2004 First Menasha Bancshares, Inc. (4) 3/17/2034 5,155 (575) 4,580 4,536 Total $ 32,063 $ (7,194) $ 24,869 $ 30,575 (1) The interest rate is 8.00% fixed. (2) The debentures, assumed in April 2013 as the result of an acquisition, have a floating rate of the three-month LIBOR plus 1.43%, adjusted quarterly. The interest rates were 1.65% and 3.32% as of December 31, 2020 and 2019, respectively. (3) The debentures, assumed in April 2016 as a result of an acquisition, have a floating rate of the three-month LIBOR plus 1.35%, adjusted quarterly. The interest rates were 1.59% and 3.31% as of December 31, 2020 and 2019, respectively. (4) The debentures, assumed in April 2017 as the result of an acquisition, have a floating rate of the three-month LIBOR plus 2.79%, adjusted quarterly. The interest rate was 3.02% and 4.69% as of December 31, 2020 and 2019, respectively.

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Schedule of weighted average assumptions for valuing stock option grants	The weighted average assumptions used in the model for valuing stock option grants were as follows. 2020 2019 2018 Dividend yield — % — % — % Expected volatility 25 % 25 % 25 % Risk-free interest rate 1.35 % 1.75 % 2.61 % Expected average life 7 years 7 years 7 years Weighted average per share fair value of options $ 20.55 $ 21.30 $ 17.36
Schedule of stock option activity	A summary of the Company’s stock option activity is summarized below. Stock Options Option Shares Weighted Average Weighted Average Remaining Life (Years) Aggregate Intrinsic Value (in thousands) Outstanding – December 31, 2017 1,643,255 $ 39.82 Granted 15,500 52.76 Exercise of stock options * (70,556) 21.52 Forfeited (6,500) 39.43 Outstanding – December 31, 2018 1,581,699 $ 40.77 7.4 $ 13,825 Granted 203,000 69.69 Exercise of stock options * (337,428) 24.15 Forfeited (3,538) 27.43 Outstanding – December 31, 2019 1,443,733 $ 48.75 7.4 $ 36,428 Granted 54,500 69.44 Exercise of stock options * (60,773) 26.51 Forfeited — — Outstanding – December 31, 2020 1,437,460 $ 50.47 6.6 $ 23,840 Exercisable – December 31, 2020 800,310 $ 46.18 6.1 $ 16,310 *The terms of the stock option agreements permit having a number of shares of stock withheld, the fair market value of which as of the date of exercise is sufficient to satisfy the exercise price and/or tax withholding requirements, and accordingly 18,952 shares, 142,752 shares, and 6,411 shares were surrendered during 2020, 2019, and 2018, respectively.
Schedule of options outstanding	The following options were outstanding at December 31, 2020. Number of Shares Weighted Average Weighted Average Outstanding Exercisable Outstanding Exercisable Outstanding Exercisable $13.73 – $30.00 82,013 77,963 $ 21.98 $ 22.27 3.1 3.2 $30.01 – $40.00 146,297 116,197 35.82 35.52 5.4 5.3 $40.01 – $50.00 801,150 478,350 48.86 48.86 6.4 6.4 $50.01 – $60.00 160,500 88,200 56.08 56.18 7.0 6.9 $60.01 – $73.52 247,500 39,600 70.16 70.01 8.9 8.9 1,437,460 800,310 $ 50.47 $ 46.18 6.6 6.1
Schedule of restricted stock	A summary of the Company’s restricted stock activity is summarized below. Restricted Stock Restricted Shares Weighted Average Grant Outstanding – December 31, 2017 30,920 $ 34.26 Granted 18,256 52.55 Vested * (19,661) 43.58 Forfeited (3) 16.50 Outstanding – December 31, 2018 29,512 $ 39.37 Granted 12,498 67.59 Vested * (19,081) 51.77 Forfeited (408) 16.50 Outstanding – December 31, 2019 22,521 $ 44.94 Granted 19,672 60.29 Vested * (23,268) 50.90 Forfeited — — Outstanding – December 31, 2020 18,925 $ 53.57 *The terms of the restricted stock agreements permit the surrender of shares to the Company upon vesting in order to satisfy applicable tax withholding at the minimum statutory withholding rate, and accordingly 4,733 shares, 4,688 shares, and 3,948 shares were surrendered during 2020, 2019, and 2018, respectively.

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of current and deferred amounts of income tax expense	The current and deferred amounts of income tax expense were as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Current $ 29,764 $ 15,353 $ 14,967 Deferred (9,288) 1,105 (1,521) Income tax expense $ 20,476 $ 16,458 $ 13,446
Schedule of income tax reconciliation	The differences between the income tax expense recognized and the amount computed by applying the statutory federal income tax rate of 21% to the income before income tax expense, less noncontrolling interest, for the years ended as indicated are included in the following table. Years Ended December 31, (in thousands) 2020 2019 2018 Tax on pretax income, less noncontrolling interest, at statutory rates $ 16,926 $ 14,931 $ 11,441 State income taxes, net of federal effect 5,030 3,672 3,308 Tax-exempt interest income (527) (609) (574) Non-deductible interest disallowance 14 29 30 Increase in cash surrender value life insurance (738) (573) (508) Non-deductible business entertainment 170 189 156 Stock-based employee compensation (839) (2,347) (232) Non-deductible compensation 272 3,122 — Sale of UFS (109) (2,176) — Other, net 277 220 (175) Income tax expense $ 20,476 $ 16,458 $ 13,446
Schedule of net deferred tax asset	The net deferred tax asset includes the following amounts of deferred tax assets and liabilities. (in thousands) December 31, 2020 December 31, 2019 Deferred tax assets: ACL-Loans $ 9,328 $ 4,985 Net operating loss carryforwards 1,692 1,808 Credit carryforwards — 43 Compensation 5,822 3,477 Purchase of noncontrolling interest 2,112 — Other 2,949 2,830 Other real estate 538 201 Total deferred tax assets 22,441 13,344 Deferred tax liabilities: Premises and equipment (1,577) (1,390) Prepaid expenses (1,010) (778) Investment securities (451) (755) Core deposit and other intangibles (1,777) (2,836) Purchase accounting adjustments to liabilities (1,969) (2,375) MSR asset (2,269) (1,391) Other (282) — Unrealized gain on securities AFS (4,959) (1,879) Total deferred tax liabilities (14,294) (11,404) Net deferred tax assets $ 8,147 $ 1,940

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Schedule of summary of the contract or notional amount of exposure to off-balance-sheet risk	A summary of the contract or notional amount of the Company’s exposure to off-balance sheet risk was as follows. (in thousands) December 31, 2020 December 31, 2019 Commitments to extend credit $ 950,287 $ 773,555 Financial standby letters of credit 8,241 10,730 Performance standby letters of credit 8,366 8,469

ASSETS GAINS (LOSSES), NET (Tab

ASSETS GAINS (LOSSES), NET (Tables)	12 Months Ended
	Dec. 31, 2020
Assets Gains (Losses), Net [Abstract]
Schedule of components of the net gain (losses) on assets	Components of the net gains (losses) on assets are as follows. Years Ended December 31, (in thousands) 2020 2019 2018 Gains (losses) on sales of securities AFS, net $ 395 $ (22) $ (212) Gains (losses) on equity securities, net (987) 1,115 77 Gains (losses) on sales of OREO, net 157 (88) 1,032 Write-downs of OREO (1,040) (300) (120) Write-down of other investment (100) (100) — Gains (losses) on sales of other investments, net — 7,442 187 Gains (losses) on sales or dispositions of other assets, net (230) (150) 205 Asset gains (losses), net $ (1,805) $ 7,897 $ 1,169

REGULATORY CAPITAL REQUIREMEN_2

REGULATORY CAPITAL REQUIREMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Regulatory Capital Requirements Under Banking Regulations [Abstract]
Schedule of Bank's actual regulatory capital amounts and ratios	The Company’s and the Bank’s actual regulatory capital amounts and ratios are presented in the following table. Actual For Capital Adequacy To Be Well Capitalized Under Prompt Corrective Action Provisions (2) (in thousands) Amount Ratio (1) Amount Ratio (1) Amount Ratio (1) December 31, 2020 Company Total risk-based capital $ 406,325 12.9 % $ 252,683 8.0 % Tier 1 risk-based capital 385,068 12.2 189,512 6.0 Common equity Tier 1 capital 361,162 11.4 142,134 4.5 Leverage 385,068 9.0 170,402 4.0 Bank Total risk-based capital $ 351,081 11.2 % $ 251,769 8.0 % $ 314,711 10.0 % Tier 1 risk-based capital 329,824 10.5 188,826 6.0 251,769 8.0 Common equity Tier 1 capital 329,824 10.5 141,620 4.5 204,562 6.5 Leverage 329,824 7.8 170,025 4.0 212,532 5.0 December 31, 2019 Company Total risk-based capital $ 404,573 13.4 % $ 241,333 8.0 % Tier 1 risk-based capital 378,608 12.6 181,000 6.0 Common equity Tier 1 capital 348,454 11.6 135,750 4.5 Leverage 378,608 11.9 127,036 4.0 Bank Total risk-based capital $ 323,432 10.8 % $ 240,551 8.0 % $ 300,688 10.0 % Tier 1 risk-based capital 309,460 10.3 180,413 6.0 240,551 8.0 Common equity Tier 1 capital 309,460 10.3 135,310 4.5 195,447 6.5 Leverage 309,460 9.8 126,660 4.0 158,325 5.0 (1) The Total risk-based capital ratio is defined as Tier 1 capital plus tier 2 capital divided by total risk-weighted assets. The Tier 1 risk-based capital ratio is defined as Tier 1 capital divided by total risk-weighted assets. CET1 risk-based capital ratio is defined as Tier 1 capital, with deductions for goodwill and other intangible assets (other than mortgage servicing assets), net of associated deferred tax liabilities, and limitations on the inclusion of deferred tax assets, mortgage servicing assets and investments in other financial institutions, in each case as provided further in the rules, divided by total risk-weighted assets. The Leverage ratio is defined as Tier 1 capital divided by the most recent quarter’s average total assets as adjusted. (2) Prompt corrective action provisions are not applicable at the bank holding company level.

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of assets and liabilities measured at fair value on a recurring basis	The following table presents the balances of assets and liabilities measured at fair value on a recurring basis for the periods presented. (in thousands) Fair Value Measurements Using Measured at Fair Value on a Recurring Basis: Total Level 1 Level 2 Level 3 December 31, 2020 U.S. government agency securities $ 63,451 $ — $ 63,451 $ — State, county and municipals 231,868 — 231,868 — Mortgage-backed securities 162,495 — 162,495 — Corporate debt securities 81,523 — 78,393 3,130 Securities AFS $ 539,337 $ — $ 536,207 $ 3,130 Other investments (equity securities) $ 3,567 $ 3,567 $ — $ — December 31, 2019 U.S. government agency securities $ 16,460 $ — $ 16,460 $ — State, county and municipals 156,393 — 156,393 — Mortgage-backed securities 195,018 — 195,018 — Corporate debt securities 81,431 — 78,301 3,130 Securities AFS $ 449,302 $ — $ 446,172 $ 3,130 Other investments (equity securities) $ 3,375 $ 3,375 $ — $ —
Schedule of changes in Level 3 securities AFS measured at fair value on a recurring basis	The following table presents the changes in Level 3 securities AFS measured at fair value on a recurring basis. (in thousands) Years Ended Level 3 Fair Value Measurements: December 31, 2020 December 31, 2019 Balance at beginning of year $ 3,130 $ 8,490 Acquired balances — 300 Paydowns/Sales/Settlements — (5,660) Balance at end of year $ 3,130 $ 3,130
Schedule of assets measured at fair value on a nonrecurring basis	The following table presents the Company’s assets measured at fair value on a nonrecurring basis, aggregated by the level in the fair value hierarchy within which those measurements fall. (in thousands) Fair Value Measurements Using Measured at Fair Value on a Nonrecurring Basis: Total Level 1 Level 2 Level 3 December 31, 2020 Collateral dependent loans $ 7,633 $ — $ — $ 7,633 OREO 3,608 — — 3,608 MSR asset 9,276 — — 9,276 December 31, 2019 Impaired loans $ 16,150 $ — $ — $ 16,150 OREO 1,000 — — 1,000 MSR asset 8,420 — — 8,420
Schedule of estimated fair values of financial instruments	The carrying amounts and estimated fair values of the Company's financial instruments are shown below. December 31, 2020 (in thousands) Carrying Estimated Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 802,859 $ 802,859 $ 802,859 $ — $ — Certificates of deposit in other banks 29,521 31,053 — 31,053 — Securities AFS 539,337 539,337 — 536,207 3,130 Other investments 27,619 27,619 3,567 20,155 3,897 Loans held for sale 21,450 22,329 — 22,329 — Loans, net 2,756,928 2,834,452 — — 2,834,452 BOLI 83,262 83,262 83,262 — — MSR asset 9,230 9,276 — — 9,276 Financial liabilities: Deposits $ 3,910,399 $ 3,917,121 $ — $ — $ 3,917,121 Long-term borrowings 53,869 53,859 — 29,488 24,371 December 31, 2019 (in thousands) Carrying Estimated Level 1 Level 2 Level 3 Financial assets: Cash and cash equivalents $ 182,059 $ 182,059 $ 182,059 $ — $ — Certificates of deposit in other banks 19,305 19,310 — 19,310 — Securities AFS 449,302 449,302 — 446,172 3,130 Other investments 24,072 24,072 3,375 16,759 3,938 Loans held for sale 2,706 2,753 — 2,753 — Loans, net 2,559,779 2,593,110 — — 2,593,110 BOLI 78,140 78,140 78,140 — — MSR asset 5,919 8,420 — — 8,420 Financial liabilities: Deposits $ 2,954,453 $ 2,956,229 $ — $ — $ 2,956,229 Long-term borrowings 67,629 66,816 — 25,075 41,741

PARENT COMPANY ONLY FINANCIAL_2

PARENT COMPANY ONLY FINANCIAL INFORMATION (Tables)	12 Months Ended
	Dec. 31, 2020
Condensed Financial Information Disclosure [Abstract]
Schedule of parent company only condensed financial statements	Condensed Parent Company only financial statements of Nicolet Bankshares, Inc. follow. Balance Sheets December 31, (in thousands) 2020 2019 Assets Cash and due from subsidiary $ 49,998 $ 70,426 Investments 6,742 6,650 Investments in subsidiaries 513,736 487,644 Goodwill (3,266) (3,266) Other assets 177 396 Total assets $ 567,387 $ 561,850 Liabilities and Stockholders’ Equity Junior subordinated debentures $ 24,869 $ 30,575 Subordinated notes — 11,993 Other liabilities 3,329 3,020 Stockholders’ equity 539,189 516,262 Total liabilities and stockholders’ equity $ 567,387 $ 561,850 Statements of Income Years Ended December 31, (in thousands) 2020 2019 2018 Interest income $ 39 $ 55 $ 52 Interest expense 2,313 2,936 2,844 Net interest expense (2,274) (2,881) (2,792) Dividend income from subsidiaries 60,215 50,363 40,775 Operating expense (886) (321) (364) Gain (loss) on investments, net (1,087) 1,015 265 Income tax benefit 1,102 506 305 Earnings before equity in undistributed income (loss) of subsidiaries 57,070 48,682 38,189 Equity in undistributed income (loss) of subsidiaries 3,052 5,959 2,847 Net income attributable to Nicolet Bankshares, Inc. $ 60,122 $ 54,641 $ 41,036 Statements of Cash Flows Years Ended December 31, (in thousands) 2020 2019 2018 Cash Flows From Operating Activities: Net income attributable to Nicolet Bankshares, Inc. $ 60,122 $ 54,641 $ 41,036 Adjustments to reconcile net income to net cash provided by operating activities: Accretion of discounts 486 515 515 (Gain) loss on investments, net 1,087 (1,015) (265) Change in other assets and liabilities, net 1,786 (421) (25) Equity in undistributed (income) loss of subsidiaries, net of dividends (3,052) (5,959) (2,847) Net cash provided by operating activities 60,429 47,761 38,414 Cash Flows from Investing Activities: Proceeds from sale of investments 185 — 708 Purchases of investments (1,179) (2,484) (920) Net cash paid in business combinations (21,644) (412) — Net cash used in investing activities (22,638) (2,896) (212) Cash Flows From Financing Activities: Purchase and retirement of common stock (42,088) (28,460) (22,749) Proceeds from issuance of common stock, net 2,055 8,742 1,800 Repayment of long-term borrowings (18,186) — — Net cash used in financing activities (58,219) (19,718) (20,949) Net increase (decrease) in cash and due from subsidiary (20,428) 25,147 17,253 Beginning cash and due from subsidiary 70,426 45,279 28,026 Ending cash and due from subsidiary $ 49,998 $ 70,426 $ 45,279

EARNINGS PER COMMON SHARE (Tabl

EARNINGS PER COMMON SHARE (Tables)	12 Months Ended
	Dec. 31, 2020
Earnings Per Share [Abstract]
Schedule of earnings per common share	Presented below are the calculations for basic and diluted earnings per common share. Years Ended December 31, (in thousands, except per share data) 2020 2019 2018 Net income attributable to Nicolet Bankshares, Inc. $ 60,122 $ 54,641 $ 41,036 Weighted average common shares outstanding 10,337 9,562 9,640 Effect of dilutive common stock awards 204 338 316 Diluted weighted average common shares outstanding 10,541 9,900 9,956 Basic earnings per common share $ 5.82 $ 5.71 $ 4.26 Diluted earnings per common share $ 5.70 $ 5.52 $ 4.12

NATURE OF BUSINESS AND SIGNIF_4

NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash	$ 0	$ 0	$ 6,000,000	$ 6,300,000
Restricted cash pledged as collateral		$ 1,900,000	$ 1,300,000	0
Loans, threshold period past due	90 days	90 days
Material loans criteria for ACL-Loans adequacy calculation		$ 250,000
Operating Lease, Liability, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities	us-gaap:OtherLiabilities
Impairment charge		$ 0	$ 762,000
Cumulative effect adjustment to retained earnings	$ 539,189,000	$ 539,189,000	$ 516,990,000	387,352,000		$ 364,879,000
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:InterestReceivableAndOtherAssets	us-gaap:InterestReceivableAndOtherAssets	us-gaap:InterestReceivableAndOtherAssets
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings	$ 252,952,000	$ 252,952,000	$ 199,005,000	144,364,000		102,391,000
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings			(6,175,000)			0
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment to retained earnings			(6,175,000)			$ 937,000
Minimum | Securities sold under agreements to repurchase
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Maturity period of repo agreements		1 day
Maximum | Securities sold under agreements to repurchase
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Maturity period of repo agreements		4 days
Core deposit intangibles:
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amortized period of core deposit intangible		10 years
Customer list intangibles
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Amortized period of core deposit intangible		12 years
Mortgage Servicing Rights
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Mortgage servicing rights, valuation allowance	1,000,000	$ 1,000,000	0	$ 0
Valuation allowance recorded		(1,000,000)	0
Impairment recorded			0
Measured at Fair Value on a Recurring Basis | Equity Securities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other investments (equity securities)	3,567,000	3,567,000	3,375,000
Measured at Fair Value on a Recurring Basis | Equity Securities | Level 2
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other investments (equity securities)	0	0	0
Measured at Fair Value on a Recurring Basis | Equity Securities | Level 3
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other investments (equity securities)	0	0	0
Measured at Fair Value on a Nonrecurring Basis | OREO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
OREO	3,608,000	3,608,000	1,000,000
Measured at Fair Value on a Nonrecurring Basis | Level 2 | OREO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
OREO	0	0	0
Measured at Fair Value on a Nonrecurring Basis | Level 3 | OREO
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
OREO	3,608,000	3,608,000	1,000,000
Estimated Fair Value
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted equity securities	27,619,000	27,619,000	24,072,000
Estimated Fair Value | Level 2
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted equity securities	20,155,000	20,155,000	16,759,000
Estimated Fair Value | Level 3
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted equity securities	3,897,000	3,897,000	$ 3,938,000
Estimated Fair Value | Measured at Fair Value on a Recurring Basis | Equity Securities
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other investments (equity securities)	$ 3,600,000	$ 3,600,000
Nicolet Joint Ventures, LLC (the "JV")
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ownership percentage in subsidiary	100.00%
Nicolet Joint Ventures, LLC (the "JV")
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Ownership percentage by noncontrolling owners					50.00%
Noncontrolling interest, ownership percentage purchased	50.00%

NATURE OF BUSINESS AND SIGNIF_5

NATURE OF BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES - Estimated useful lives of premises and equipment (Details)	12 Months Ended
	Dec. 31, 2020
Minimum | Building and improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	25 years
Minimum | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	5 years
Minimum | Furniture and equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	3 years
Maximum | Building and improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	40 years
Maximum | Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	15 years
Maximum | Furniture and equipment
Property, Plant and Equipment [Line Items]
Estimated useful lives of new premises and equipment	10 years

ACQUISITIONS - Narrative (Detai

ACQUISITIONS - Narrative (Details) $ / shares in Units, $ in Thousands	Aug. 21, 2020USD ($)Branch	May 18, 2020USD ($)	Nov. 08, 2019USD ($)$ / sharesshares	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)	Aug. 20, 2020	Nov. 12, 2019Branch	Nov. 07, 2019
Business Acquisition [Line Items]
Goodwill				$ 11,953	$ 44,594
Value of cash consideration				$ 21,820
Commerce Financial Holdings, Inc.
Business Acquisition [Line Items]
Common stock surrendered		$ 100
Advantage Community Bancshares, Inc.
Business Acquisition [Line Items]
Percentage of assets represented by acquiree						0.04
Choice Bancorp Inc.
Business Acquisition [Line Items]
Percentage of assets represented by acquiree								0.12
Advantage Community Bancshares, Inc.
Business Acquisition [Line Items]
Number of branches | Branch	4
Assets acquired	$ 172,000
Loans acquired	88,000
Deposits acquired	141,000
Goodwill	12,000
Advantage Community Bancshares, Inc. | Core deposit intangibles
Business Acquisition [Line Items]
Intangible assets acquired	$ 1,000
Choice Bancorp Inc.
Business Acquisition [Line Items]
Number of branches | Branch							2
Assets acquired			$ 457,000
Loans acquired			348,000
Deposits acquired			289,000
Goodwill			$ 45,000
Number of common stock issued for consideration (in shares) | shares			1,184,102
Number of common stock for each outstanding share of common stock			0.00497
Common stock issued amount			$ 79,800
Price per share for stock issued in consideration (in dollars per share) | $ / shares			$ 67.39
Value of cash consideration			$ 1,700
Direct stock issuance costs for the merger charged against additional paid in capital			200
Choice Bancorp Inc. | Core deposit intangibles
Business Acquisition [Line Items]
Intangible assets acquired			$ 1,700
Commerce Financial Holdings, Inc.
Business Acquisition [Line Items]
Termination costs		$ 500

SECURITIES AVAILABLE FOR SALE -

SECURITIES AVAILABLE FOR SALE - Amortized costs and fair values of securities available for sale (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 521,876	$ 443,249
Gross Unrealized Gains	17,550	6,967
Gross Unrealized Losses	89	914
Fair Value	$ 539,337	$ 449,302
Fair Value as % of Total	100.00%	100.00%
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 63,162	$ 16,516
Gross Unrealized Gains	289	4
Gross Unrealized Losses	0	60
Fair Value	$ 63,451	$ 16,460
Fair Value as % of Total	12.00%	4.00%
State, county and municipals
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 226,493	$ 155,501
Gross Unrealized Gains	5,386	1,049
Gross Unrealized Losses	11	157
Fair Value	$ 231,868	$ 156,393
Fair Value as % of Total	43.00%	35.00%
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 156,148	$ 193,223
Gross Unrealized Gains	6,425	2,492
Gross Unrealized Losses	78	697
Fair Value	$ 162,495	$ 195,018
Fair Value as % of Total	30.00%	43.00%
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 76,073	$ 78,009
Gross Unrealized Gains	5,450	3,422
Gross Unrealized Losses	0	0
Fair Value	$ 81,523	$ 81,431
Fair Value as % of Total	15.00%	18.00%

SECURITIES AVAILABLE FOR SALE_2

SECURITIES AVAILABLE FOR SALE - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
AFS securities pledged as collateral	$ 146,000,000	$ 166,000,000
Allowance for credit losses on securities AFS	0
Other-than-temporary impairment loss recognized on securities AFS	0	0
Available-for-sale Securities
Debt Securities, Available-for-sale [Line Items]
Accrued interest on securities AFS	$ 2,300,000	$ 2,200,000

SECURITIES AVAILABLE FOR SALE_3

SECURITIES AVAILABLE FOR SALE - Gross unrealized losses and the related fair value of securities available for sale (Details) $ in Thousands	Dec. 31, 2020USD ($)Security	Dec. 31, 2019USD ($)Security
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	$ 15,793	$ 73,112
Less than 12 months, Unrealized Losses	82	379
12 months or more, Fair Value	492	65,967
12 months or more, Unrealized Losses	7	535
Total, Fair Value	16,285	139,079
Total, Unrealized Losses	$ 89	$ 914
Number of Securities | Security	31	212
U.S. government agency securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value		$ 1,035
Less than 12 months, Unrealized Losses		2
12 months or more, Fair Value		11,091
12 months or more, Unrealized Losses		58
Total, Fair Value		12,126
Total, Unrealized Losses		$ 60
Number of Securities | Security		6
US States and Political Subdivisions Debt Securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	$ 5,181	$ 22,451
Less than 12 months, Unrealized Losses	11	132
12 months or more, Fair Value	0	7,605
12 months or more, Unrealized Losses	0	25
Total, Fair Value	5,181	30,056
Total, Unrealized Losses	$ 11	$ 157
Number of Securities | Security	9	56
Mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 months, Fair Value	$ 10,612	$ 49,626
Less than 12 months, Unrealized Losses	71	245
12 months or more, Fair Value	492	47,271
12 months or more, Unrealized Losses	7	452
Total, Fair Value	11,104	96,897
Total, Unrealized Losses	$ 78	$ 697
Number of Securities | Security	22	150

SECURITIES AVAILABLE FOR SALE_4

SECURITIES AVAILABLE FOR SALE - Amortized cost and fair values of securities available for sale at by contractual maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Amortized Cost
Due in less than one year	$ 85,317
Due in one year through five years	168,302
Due after five years through ten years	97,662
Due after ten years	14,447
Allocated and single maturity date	365,728
Amortized Cost	521,876	$ 443,249
Fair Value
Due in less than one year	85,712
Due in one year through five years	174,975
Due after five years through ten years	100,445
Due after ten years	15,710
Allocated and single maturity date	376,842
Fair Value	539,337	449,302
Mortgage-backed securities
Amortized Cost
Mortgage-backed securities	156,148
Amortized Cost	156,148	193,223
Fair Value
Mortgage-backed securities	162,495
Fair Value	$ 162,495	$ 195,018

SECURITIES AVAILABLE FOR SALE_5

SECURITIES AVAILABLE FOR SALE - Proceeds from sales of securities AFS (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Abstract]
Gross gains	$ 395	$ 152	$ 0
Gross losses	0	(174)	(212)
Gains (losses) on sales of securities AFS, net	395	(22)	(212)
Proceeds from sales of securities AFS	$ 19,045	$ 23,405	$ 5,280

LOANS, ALLOWANCE FOR CREDIT L_2

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Summary of loan composition (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 2,789,101	$ 2,573,751
Less ACL-Loans	32,173	13,972	$ 13,153	$ 12,653
Loans, net	$ 2,756,928	$ 2,559,779
ACL-Loans to loans	1.15%	0.54%
% of Total	100.00%	100.00%
Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 521,300
Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	31,695	$ 30,211
Less ACL-Loans	$ 557	$ 344	304
% of Total	1.00%	1.00%
Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 750,718	$ 806,189
Less ACL-Loans	$ 11,644	$ 5,471	5,271
% of Total	27.00%	31.00%
Commercial Portfolio Segment | Paycheck Protection Program (“PPP”) loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 186,016	$ 0
% of Total	7.00%	0.00%
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 521,300	$ 496,372
Less ACL-Loans	$ 5,872	$ 3,010	2,847
% of Total	19.00%	19.00%
Commercial Portfolio Segment | Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 109,629	$ 95,450
Less ACL-Loans	$ 1,395	$ 579	422
% of Total	4.00%	4.00%
Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 460,721	$ 443,218
Less ACL-Loans	$ 5,441	$ 1,600	1,470
% of Total	16.00%	17.00%
Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 131,283	$ 92,970
Less ACL-Loans	$ 984	$ 414	510
% of Total	5.00%	4.00%
Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 444,155	$ 432,167
Less ACL-Loans	$ 4,773	$ 1,669	1,646
% of Total	16.00%	17.00%
Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 111,877	$ 122,771
Less ACL-Loans	$ 1,086	$ 517	472
% of Total	4.00%	5.00%
Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans	$ 41,707	$ 54,403
Less ACL-Loans	$ 421	$ 368	$ 211
% of Total	1.00%	2.00%

LOANS, ALLOWANCE FOR CREDIT L_3

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY- Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)Loan	Dec. 31, 2019USD ($)Loan
Receivables [Abstract]
Accrued interest on loans	$ 7	$ 7
Number of loans classified as troubled debt restructuring, | Loan	11	5
Troubled debt restructurings, postmodification balance	$ 5.5	$ 1.1
Troubled debt restructurings, postmodification balance, nonaccrual	3.4
Financing Receivable, Performing, Troubled Debt Restructuring, Postmodification	2.1
Troubled debt restructurings, premodification balance	$ 6.5	$ 1.4
Number of loans classified as troubled debt with subsequent default | Loan	0

LOANS, ALLOWANCE FOR CREDIT L_4

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Summary of allowance for credit losses - loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 13,972	$ 13,153	$ 12,653
Provision for credit losses	10,300	1,200	1,600
Charge-offs	(1,689)	(927)	(1,213)
Recoveries	305	546	113
Net (charge-offs) recoveries	(1,384)	(381)	(1,100)
Ending balance	32,173	13,972	$ 13,153
Total impact for adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	9,285
Ending balance		9,285
Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	8,488
Ending balance		8,488
Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 797
Ending balance		$ 797

LOANS, ALLOWANCE FOR CREDIT L_5

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Summary of changes in ACL-Loans by portfolio segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 13,972	$ 13,153	$ 12,653
Provision for credit losses	10,300	1,200	1,600
Charge-offs	(1,689)	(927)	(1,213)
Recoveries	305	546	113
Net (charge-offs) recoveries	(1,384)	(381)	(1,100)
Ending balance	$ 32,173	$ 13,972	13,153
As % of ACL-Loans	100.00%	100.00%
Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 8,488
Ending balance		$ 8,488
Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	797
Ending balance		797
Retail & other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	344	304
Provision for credit losses	208	338
Charge-offs	(155)	(347)
Recoveries	26	49
Net (charge-offs) recoveries	(129)	(298)
Ending balance	$ 557	$ 344	304
As % of ACL-Loans	2.00%	2.00%
Retail & other | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 134
Ending balance		$ 134
Retail & other | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0
Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	5,471	5,271
Provision for credit losses	3,106	(61)
Charge-offs	(812)	(159)
Recoveries	120	420
Net (charge-offs) recoveries	(692)	261
Ending balance	$ 11,644	$ 5,471	5,271
As % of ACL-Loans	36.00%	39.00%
Commercial Portfolio Segment | Commercial & industrial | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 2,962
Ending balance		$ 2,962
Commercial Portfolio Segment | Commercial & industrial | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	797
Ending balance		797
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	3,010	2,847
Provision for credit losses	2,062	254
Charge-offs	(530)	(93)
Recoveries	81	2
Net (charge-offs) recoveries	(449)	(91)
Ending balance	$ 5,872	$ 3,010	2,847
As % of ACL-Loans	18.00%	22.00%
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,249
Ending balance		$ 1,249
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0
Commercial Portfolio Segment | Agricultural
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	579	422
Provision for credit losses	455	157
Charge-offs	0	0
Recoveries	0	0
Net (charge-offs) recoveries	0	0
Ending balance	$ 1,395	$ 579	422
As % of ACL-Loans	4.00%	4.00%
Commercial Portfolio Segment | Agricultural | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 361
Ending balance		$ 361
Commercial Portfolio Segment | Agricultural | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0
Commercial Real Estate Portfolio Segment | CRE investment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,600	1,470
Provision for credit losses	2,061	130
Charge-offs	(190)	0
Recoveries	0	0
Net (charge-offs) recoveries	(190)	0
Ending balance	$ 5,441	$ 1,600	1,470
As % of ACL-Loans	17.00%	11.00%
Commercial Real Estate Portfolio Segment | CRE investment | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,970
Ending balance		$ 1,970
Commercial Real Estate Portfolio Segment | CRE investment | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0
Commercial Real Estate Portfolio Segment | Construction & land development
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	414	510
Provision for credit losses	519	(96)
Charge-offs	0	0
Recoveries	0	0
Net (charge-offs) recoveries	0	0
Ending balance	$ 984	$ 414	510
As % of ACL-Loans	3.00%	3.00%
Commercial Real Estate Portfolio Segment | Construction & land development | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 51
Ending balance		$ 51
Commercial Real Estate Portfolio Segment | Construction & land development | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0
Residential | Residential first mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	1,669	1,646
Provision for credit losses	1,809	9
Charge-offs	(2)	(22)
Recoveries	11	36
Net (charge-offs) recoveries	9	14
Ending balance	$ 4,773	$ 1,669	1,646
As % of ACL-Loans	15.00%	12.00%
Residential | Residential first mortgage | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1,286
Ending balance		$ 1,286
Residential | Residential first mortgage | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0
Residential | Residential junior mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	517	472
Provision for credit losses	151	86
Charge-offs	0	(80)
Recoveries	67	39
Net (charge-offs) recoveries	67	(41)
Ending balance	$ 1,086	$ 517	472
As % of ACL-Loans	4.00%	4.00%
Residential | Residential junior mortgage | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 351
Ending balance		$ 351
Residential | Residential junior mortgage | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	0
Ending balance		0
Residential | Residential construction
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	368	211
Provision for credit losses	(71)	383
Charge-offs	0	(226)
Recoveries	0	0
Net (charge-offs) recoveries	0	(226)
Ending balance	$ 421	$ 368	$ 211
As % of ACL-Loans	1.00%	3.00%
Residential | Residential construction | Adoption of CECL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 124
Ending balance		$ 124
Residential | Residential construction | Initial PCD ACL
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 0
Ending balance		$ 0

LOANS, ALLOWANCE FOR CREDIT L_6

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Collateral dependent loans by portfolio segment (Details) $ in Thousands	Dec. 31, 2020USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	$ 8,877
Without an Allowance	7,180
With an Allowance	1,697
Allowance Allocation	1,244
Retail & other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Without an Allowance	0
With an Allowance	0
Allowance Allocation	0
Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	2,195
Without an Allowance	501
With an Allowance	1,694
Allowance Allocation	1,241
Commercial Portfolio Segment | PPP loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Without an Allowance	0
With an Allowance	0
Allowance Allocation	0
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	3,519
Without an Allowance	3,519
With an Allowance	0
Allowance Allocation	0
Commercial Portfolio Segment | Agricultural
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	1,381
Without an Allowance	1,378
With an Allowance	3
Allowance Allocation	3
Commercial Real Estate Portfolio Segment | CRE investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	1,474
Without an Allowance	1,474
With an Allowance	0
Allowance Allocation	0
Commercial Real Estate Portfolio Segment | Construction & land development
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	308
Without an Allowance	308
With an Allowance	0
Allowance Allocation	0
Residential | Residential first mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Without an Allowance	0
With an Allowance	0
Allowance Allocation	0
Residential | Residential junior mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Without an Allowance	0
With an Allowance	0
Allowance Allocation	0
Residential | Residential construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Without an Allowance	0
With an Allowance	0
Allowance Allocation	0
Real Estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	5,885
Real Estate | Retail & other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Real Estate | Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Real Estate | Commercial Portfolio Segment | PPP loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Real Estate | Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	3,519
Real Estate | Commercial Portfolio Segment | Agricultural
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	584
Real Estate | Commercial Real Estate Portfolio Segment | CRE investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	1,474
Real Estate | Commercial Real Estate Portfolio Segment | Construction & land development
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	308
Real Estate | Residential | Residential first mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Real Estate | Residential | Residential junior mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Real Estate | Residential | Residential construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	2,992
Other Business Assets | Retail & other
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets | Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	2,195
Other Business Assets | Commercial Portfolio Segment | PPP loans
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets | Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets | Commercial Portfolio Segment | Agricultural
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	797
Other Business Assets | Commercial Real Estate Portfolio Segment | CRE investment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets | Commercial Real Estate Portfolio Segment | Construction & land development
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets | Residential | Residential first mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets | Residential | Residential junior mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	0
Other Business Assets | Residential | Residential construction
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans	$ 0

LOANS, ALLOWANCE FOR CREDIT L_7

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Impaired loans by portfolio segment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019USD ($)
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 16,891
Unpaid  Principal Balance	20,300
Related Allowance	741
Average Recorded Investment	16,998
Interest Income Recognized	2,063
Retail & other
Financing Receivable, Impaired [Line Items]
Recorded Investment	12
Unpaid  Principal Balance	12
Related Allowance	0
Average Recorded Investment	12
Interest Income Recognized	0
Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Impaired [Line Items]
Recorded Investment	5,932
Unpaid  Principal Balance	7,950
Related Allowance	625
Average Recorded Investment	5,405
Interest Income Recognized	1,170
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,430
Unpaid  Principal Balance	4,016
Related Allowance	0
Average Recorded Investment	3,677
Interest Income Recognized	256
Commercial Portfolio Segment | Agricultural
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,134
Unpaid  Principal Balance	2,172
Related Allowance	116
Average Recorded Investment	2,311
Interest Income Recognized	37
Commercial Real Estate Portfolio Segment | CRE investment
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,426
Unpaid  Principal Balance	2,790
Related Allowance	0
Average Recorded Investment	2,497
Interest Income Recognized	364
Commercial Real Estate Portfolio Segment | Construction & land development
Financing Receivable, Impaired [Line Items]
Recorded Investment	382
Unpaid  Principal Balance	382
Related Allowance	0
Average Recorded Investment	460
Interest Income Recognized	0
Residential | Residential first mortgage
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,357
Unpaid  Principal Balance	2,629
Related Allowance	0
Average Recorded Investment	2,412
Interest Income Recognized	178
Residential | Residential junior mortgage
Financing Receivable, Impaired [Line Items]
Recorded Investment	218
Unpaid  Principal Balance	349
Related Allowance	0
Average Recorded Investment	224
Interest Income Recognized	58
Residential | Residential construction
Financing Receivable, Impaired [Line Items]
Recorded Investment	0
Unpaid  Principal Balance	0
Related Allowance	0
Average Recorded Investment	0
Interest Income Recognized	$ 0

LOANS, ALLOWANCE FOR CREDIT L_8

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Summary of loans by past due status (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	$ 2,778,881	$ 2,552,360
Total	$ 2,789,101	$ 2,573,751
Percent of current loans	99.60%	99.20%
Percent of total loans	100.00%	100.00%
30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 765	$ 7,269
Percent past due	0.00%	0.30%
90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 9,455	$ 14,122
Percent past due	0.40%	0.50%
Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total	$ 521,300
Retail & other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	31,505	$ 30,100
Total	31,695	30,211
Retail & other | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	102	110
Retail & other | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	88	1
Commercial Portfolio Segment | Commercial & industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	748,072	798,211
Total	750,718	806,189
Commercial Portfolio Segment | Commercial & industrial | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	1,729
Commercial Portfolio Segment | Commercial & industrial | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	2,646	6,249
Commercial Portfolio Segment | PPP loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	186,016
Total	186,016	0
Commercial Portfolio Segment | PPP loans | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0
Commercial Portfolio Segment | PPP loans | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	519,431	492,949
Total	521,300	496,372
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	112
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,869	3,311
Commercial Portfolio Segment | Agricultural
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	107,792	93,552
Total	109,629	95,450
Commercial Portfolio Segment | Agricultural | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	7	0
Commercial Portfolio Segment | Agricultural | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,830	1,898
Commercial Real Estate Portfolio Segment | CRE investment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	459,233	442,145
Total	460,721	443,218
Commercial Real Estate Portfolio Segment | CRE investment | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	0
Commercial Real Estate Portfolio Segment | CRE investment | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	1,488	1,073
Commercial Real Estate Portfolio Segment | Construction & land development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	130,956	90,887
Total	131,283	92,970
Commercial Real Estate Portfolio Segment | Construction & land development | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	2,063
Commercial Real Estate Portfolio Segment | Construction & land development | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	327	20
Residential | Residential first mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	442,719	428,341
Total	444,155	432,167
Residential | Residential first mortgage | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	613	2,736
Residential | Residential first mortgage | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	823	1,090
Residential | Residential junior mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	111,450	122,074
Total	111,877	122,771
Residential | Residential junior mortgage | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	43	217
Residential | Residential junior mortgage | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	384	480
Residential | Residential construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Current	41,707	54,101
Total	41,707	54,403
Residential | Residential construction | 30-89 Days Past Due (accruing)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	0	302
Residential | Residential construction | 90 Days & Over or nonaccrual
Accounts, Notes, Loans and Financing Receivable [Line Items]
Past Due	$ 0	$ 0

LOANS, ALLOWANCE FOR CREDIT L_9

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Nonaccrual loans by portfolio segment (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 9,455	$ 14,122
Percent of total loans	0.40%	0.50%
% to Total	100.00%	100.00%
Retail & other
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 88	$ 1
% to Total	1.00%	0.00%
Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 2,646	$ 6,249
% to Total	28.00%	44.00%
Commercial Portfolio Segment | Paycheck Protection Program (“PPP”) loans
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Total	0.00%	0.00%
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 1,869	$ 3,311
% to Total	20.00%	23.00%
Commercial Portfolio Segment | Agricultural
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 1,830	$ 1,898
% to Total	19.00%	14.00%
Commercial Real Estate Portfolio Segment | CRE investment
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 1,488	$ 1,073
% to Total	16.00%	8.00%
Commercial Real Estate Portfolio Segment | Construction & land development
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 327	$ 20
% to Total	3.00%	0.00%
Residential | Residential first mortgage
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 823	$ 1,090
% to Total	9.00%	8.00%
Residential | Residential junior mortgage
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 384	$ 480
% to Total	4.00%	3.00%
Residential | Residential construction
Financing Receivable, Past Due [Line Items]
Nonaccrual loans	$ 0	$ 0
% to Total	0.00%	0.00%

LOANS, ALLOWANCE FOR CREDIT _10

LOANS, ALLOWANCE FOR CREDIT LOSSES - LOANS, AND CREDIT QUALITY - Summary of loans by loan risk categories (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 800,139
2019	400,410
2018	299,024
2017	270,810
2016	153,024
Prior	519,961
Revolving	344,080
Revolving to Term	1,653
Total	$ 2,789,101	$ 2,573,751
Percent of total loans	100.00%	100.00%
Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 2,668,095	$ 2,457,922
Percent of total loans	95.70%	95.50%
Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 78,864	$ 63,966
Percent of total loans	2.80%	2.50%
Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 12,053	$ 15,152
Percent of total loans	0.40%	0.60%
Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 30,089	$ 36,711
Percent of total loans	1.10%	1.40%
Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Credit Quality Indicator [Line Items]
Total	$ 521,300
Retail & other
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,099
2019	5,213
2018	1,964
2017	1,676
2016	752
Prior	1,389
Revolving	12,602
Revolving to Term	0
Total	31,695	$ 30,211
Retail & other | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	8,083
2019	5,213
2018	1,942
2017	1,676
2016	752
Prior	1,339
Revolving	12,602
Revolving to Term	0
Total	31,607	30,210
Retail & other | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	0	0
Retail & other | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	0	0
Retail & other | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	16
2019	0
2018	22
2017	0
2016	0
Prior	50
Revolving	0
Revolving to Term	0
Total	88	1
Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Credit Quality Indicator [Line Items]
2020	350,093
2019	125,373
2018	105,530
2017	78,532
2016	23,402
Prior	46,740
Revolving	207,064
Revolving to Term	0
Total	936,734
Commercial Portfolio Segment | Commercial & industrial | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	348,274
2019	121,989
2018	98,920
2017	72,027
2016	21,613
Prior	39,454
Revolving	183,858
Revolving to Term	0
Total	886,135
Commercial Portfolio Segment | Commercial & industrial | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,416
2019	2,239
2018	4,486
2017	527
2016	1,638
Prior	4,151
Revolving	18,994
Revolving to Term	0
Total	33,451
Commercial Portfolio Segment | Commercial & industrial | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	69
2019	19
2018	735
2017	5,315
2016	29
Prior	32
Revolving	1,923
Revolving to Term	0
Total	8,122
Commercial Portfolio Segment | Commercial & industrial | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	334
2019	1,126
2018	1,389
2017	663
2016	122
Prior	3,103
Revolving	2,289
Revolving to Term	0
Total	9,026
Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Total	750,718	806,189
Commercial Portfolio Segment | Commercial & industrial | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
Total	700,119	765,073
Commercial Portfolio Segment | Commercial & industrial | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total	33,451	20,199
Commercial Portfolio Segment | Commercial & industrial | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total	8,122	7,663
Commercial Portfolio Segment | Commercial & industrial | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total	9,026	13,254
Commercial Portfolio Segment | Paycheck Protection Program (“PPP”) loans
Financing Receivable, Credit Quality Indicator [Line Items]
Total	186,016	0
Commercial Portfolio Segment | Paycheck Protection Program (“PPP”) loans | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	186,000
Total	186,016
Commercial Portfolio Segment | Paycheck Protection Program (“PPP”) loans | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
Commercial Portfolio Segment | Paycheck Protection Program (“PPP”) loans | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
Commercial Portfolio Segment | Paycheck Protection Program (“PPP”) loans | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”)
Financing Receivable, Credit Quality Indicator [Line Items]
2020	93,731
2019	75,327
2018	79,538
2017	62,997
2016	46,144
Prior	162,693
Revolving	870
Revolving to Term	0
Total	521,300	496,372
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	90,702
2019	74,029
2018	78,013
2017	52,911
2016	45,042
Prior	150,624
Revolving	870
Revolving to Term	0
Total	492,191	464,661
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	42
2019	623
2018	1,349
2017	7,541
2016	1,102
Prior	5,842
Revolving	0
Revolving to Term	0
Total	16,499	20,855
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	1,710
2016	0
Prior	706
Revolving	0
Revolving to Term	0
Total	2,416	953
Commercial Portfolio Segment | Owner-occupied commercial real estate (“CRE”) | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	2,987
2019	675
2018	176
2017	835
2016	0
Prior	5,521
Revolving	0
Revolving to Term	0
Total	10,194	9,903
Commercial Portfolio Segment | Agricultural
Financing Receivable, Credit Quality Indicator [Line Items]
2020	14,753
2019	5,652
2018	8,307
2017	10,353
2016	4,758
Prior	43,875
Revolving	21,931
Revolving to Term	0
Total	109,629	95,450
Commercial Portfolio Segment | Agricultural | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	13,719
2019	5,652
2018	7,580
2017	9,745
2016	2,613
Prior	32,702
Revolving	21,513
Revolving to Term	0
Total	93,524	77,082
Commercial Portfolio Segment | Agricultural | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	1,034
2019	0
2018	701
2017	169
2016	644
Prior	6,131
Revolving	356
Revolving to Term	0
Total	9,035	6,785
Commercial Portfolio Segment | Agricultural | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	329
2016	390
Prior	0
Revolving	0
Revolving to Term	0
Total	719	3,275
Commercial Portfolio Segment | Agricultural | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	26
2017	110
2016	1,111
Prior	5,042
Revolving	62
Revolving to Term	0
Total	6,351	8,308
Commercial Real Estate Portfolio Segment | CRE investment
Financing Receivable, Credit Quality Indicator [Line Items]
2020	82,518
2019	78,841
2018	40,928
2017	71,723
2016	33,369
Prior	148,087
Revolving	5,255
Revolving to Term	0
Total	460,721	443,218
Commercial Real Estate Portfolio Segment | CRE investment | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	82,518
2019	78,841
2018	40,881
2017	69,643
2016	31,541
Prior	137,048
Revolving	5,255
Revolving to Term	0
Total	445,727	430,794
Commercial Real Estate Portfolio Segment | CRE investment | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	47
2017	1,284
2016	1,828
Prior	9,073
Revolving	0
Revolving to Term	0
Total	12,232	8,085
Commercial Real Estate Portfolio Segment | CRE investment | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	796
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	796	2,578
Commercial Real Estate Portfolio Segment | CRE investment | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	1,966
Revolving	0
Revolving to Term	0
Total	1,966	1,761
Commercial Real Estate Portfolio Segment | Construction & land development
Financing Receivable, Credit Quality Indicator [Line Items]
2020	67,578
2019	31,106
2018	15,869
2017	2,749
2016	2,083
Prior	7,768
Revolving	4,130
Revolving to Term	0
Total	131,283	92,970
Commercial Real Estate Portfolio Segment | Construction & land development | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	67,578
2019	30,733
2018	15,209
2017	2,204
2016	2,083
Prior	7,266
Revolving	3,675
Revolving to Term	0
Total	128,748	90,523
Commercial Real Estate Portfolio Segment | Construction & land development | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	373
2018	660
2017	545
2016	0
Prior	23
Revolving	455
Revolving to Term	0
Total	2,056	2,213
Commercial Real Estate Portfolio Segment | Construction & land development | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	0	15
Commercial Real Estate Portfolio Segment | Construction & land development | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	479
Revolving	0
Revolving to Term	0
Total	479	219
Residential | Residential first mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2020	146,744
2019	65,375
2018	42,830
2017	41,517
2016	41,647
Prior	105,750
Revolving	287
Revolving to Term	5
Total	444,155	432,167
Residential | Residential first mortgage | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	146,744
2019	64,013
2018	40,388
2017	41,245
2016	41,274
Prior	103,094
Revolving	287
Revolving to Term	5
Total	437,050	424,044
Residential | Residential first mortgage | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	925
2018	2,245
2017	256
2016	364
Prior	1,714
Revolving	0
Revolving to Term	0
Total	5,504	4,677
Residential | Residential first mortgage | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	0	668
Residential | Residential first mortgage | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	437
2018	197
2017	16
2016	9
Prior	942
Revolving	0
Revolving to Term	0
Total	1,601	2,778
Residential | Residential junior mortgage
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,936
2019	4,338
2018	3,663
2017	1,087
2016	869
Prior	3,395
Revolving	91,941
Revolving to Term	1,648
Total	111,877	122,771
Residential | Residential junior mortgage | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,936
2019	4,338
2018	3,663
2017	1,060
2016	869
Prior	3,131
Revolving	91,816
Revolving to Term	1,648
Total	111,461	122,249
Residential | Residential junior mortgage | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	32
Revolving	0
Revolving to Term	0
Total	32	35
Residential | Residential junior mortgage | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	0	0
Residential | Residential junior mortgage | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	27
2016	0
Prior	232
Revolving	125
Revolving to Term	0
Total	384	487
Residential | Residential construction
Financing Receivable, Credit Quality Indicator [Line Items]
2020	31,687
2019	9,185
2018	395
2017	176
2016	0
Prior	264
Revolving	0
Revolving to Term	0
Total	41,707	54,403
Residential | Residential construction | Grades 1-4
Financing Receivable, Credit Quality Indicator [Line Items]
2020	31,687
2019	9,185
2018	395
2017	121
2016	0
Prior	264
Revolving	0
Revolving to Term	0
Total	41,652	53,286
Residential | Residential construction | Grade 5
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	55
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	55	1,117
Residential | Residential construction | Grade 6
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	0	0
Residential | Residential construction | Grade 7
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving	0
Revolving to Term	0
Total	$ 0	$ 0

PREMISES AND EQUIPMENT - Summar

PREMISES AND EQUIPMENT - Summary of premises and equipment, less accumulated depreciation (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 92,365	$ 86,943
Less accumulated depreciation and amortization	32,421	30,474
Premises and equipment, net	59,944	56,469
Land
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	6,344	7,418
Land improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	3,950	3,865
Building and improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	54,989	50,818
Leasehold improvements
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	4,381	4,580
Furniture and equipment
Property, Plant and Equipment [Line Items]
Premises and equipment, gross	$ 22,701	$ 20,262

PREMISES AND EQUIPMENT - Narrat

PREMISES AND EQUIPMENT - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)Branch	Dec. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 4,400	$ 3,800	$ 4,400
Rent expense	$ 1,000	1,200
Rent expense			1,400
Number of branches closed | Branch	8
Number of branches closed, owned locations | Branch	5
Number of branches closed, leased locations | Branch	3
Accelerated depreciation	$ 500
Write-down upon transfer to OREO	1,040	300	$ 120
Lease termination charge	$ 1,000	$ 700
Minimum
Property, Plant and Equipment [Line Items]
Renewal term on operating leases	5 years
Maximum
Property, Plant and Equipment [Line Items]
Renewal term on operating leases	10 years
Land and Building | Minimum
Property, Plant and Equipment [Line Items]
Remaining lease term on operating leases	1 year
Land and Building | Maximum
Property, Plant and Equipment [Line Items]
Remaining lease term on operating leases	10 years

PREMISES AND EQUIPMENT - Other

PREMISES AND EQUIPMENT - Other Information Related To Operating Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Abstract]
Operating lease cost	$ 834	$ 970
Variable lease cost	169	233
Net lease cost	$ 1,003	$ 1,203
Weighted average remaining lease term (years)	5 years 1 month 6 days	4 years 3 months 18 days
Weighted average discount rate	2.00%	2.50%

PREMISES AND EQUIPMENT - Minimu

PREMISES AND EQUIPMENT - Minimum annual rentals under these noncancelable agreements with remaining terms in excess of one year (Details) $ in Thousands	Dec. 31, 2020USD ($)
Property, Plant and Equipment [Abstract]
2021	$ 920
2022	780
2023	497
2024	391
2025	106
Thereafter	507
Total future minimum lease payments	3,201
Less: amount representing interest	(63)
Present value of net future minimum lease payments	$ 3,138

GOODWILL AND OTHER INTANGIBLE_3

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS - Summary of Goodwill and Other Intangibles (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 163,151	$ 151,198	$ 107,366
Other intangibles	12,202	14,769
Goodwill and other intangibles, net	175,353	165,967
Core deposit intangibles
Finite-Lived Intangible Assets [Line Items]
Other intangibles	8,837	10,897
Customer list intangibles:
Finite-Lived Intangible Assets [Line Items]
Other intangibles	$ 3,365	$ 3,872

GOODWILL AND OTHER INTANGIBLE_4

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS - Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Goodwill:
Goodwill at beginning of year	$ 151,198	$ 107,366
Acquisition	11,953	44,594
Impairment	0	(762)
Goodwill at end of year	$ 163,151	$ 151,198

GOODWILL AND OTHER INTANGIBLE_5

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS - Other Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Net book value	$ 12,202	$ 14,769
Amortization during the period	3,567	3,872	$ 4,389
Core deposit intangibles:
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	31,715	30,715
Accumulated amortization	(22,878)	(19,818)
Net book value	8,837	10,897
Additions during the period	1,000	1,700
Amortization during the period	3,060	3,365
Customer list intangibles:
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	5,523	5,523
Accumulated amortization	(2,158)	(1,651)
Net book value	3,365	3,872
Amortization during the period	$ 507	$ 507

GOODWILL AND OTHER INTANGIBLE_6

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS - Mortgage Servicing Rights (Details) - Mortgage Servicing Rights - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
MSR asset:
MSR asset at beginning of year	$ 5,919,000	$ 3,749,000
Capitalized MSR	5,256,000	2,876,000
MSR asset acquired	529,000	160,000
Amortization during the period	(1,474,000)	(866,000)
MSR asset at end of year	10,230,000	5,919,000
Valuation allowance:
Valuation allowance at beginning of year	0	0
Additions	(1,000,000)	0
Valuation allowance at end of year	(1,000,000)	0
MSR asset, net	9,230,000	5,919,000
Fair value of MSR asset at end of period	9,276,000	8,420,000
Residential mortgage loans serviced for others	$ 1,250,206,000	$ 847,756,000
Net book value of MSR asset to loans serviced for others	0.74%	0.70%

GOODWILL AND OTHER INTANGIBLE_7

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Mortgage Servicing Rights
Servicing Assets at Fair Value [Line Items]
Valuation allowance recorded	$ 1,000,000	$ 0

GOODWILL AND OTHER INTANGIBLE_8

GOODWILL AND OTHER INTANGIBLES AND MORTGAGE SERVICING RIGHTS - Estimated Future Amortization Expense (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Core Deposit and Customer List Intangibles
Net book value	$ 12,202	$ 14,769
Core deposit intangibles
Core Deposit and Customer List Intangibles
2021	2,643
2022	2,150
2023	1,633
2024	1,130
2025	670
Thereafter	611
Net book value	8,837	10,897
Customer list intangibles:
Core Deposit and Customer List Intangibles
2021	507
2022	507
2023	483
2024	449
2025	449
Thereafter	970
Net book value	3,365	$ 3,872
Mortgage Servicing Rights
Core Deposit and Customer List Intangibles
2021	1,771
2022	1,740
2023	1,635
2024	1,225
2025	876
Thereafter	2,983
Net book value	$ 10,230

DEPOSITS - Maturities of time d

DEPOSITS - Maturities of time deposits (Details) $ in Thousands	Dec. 31, 2020USD ($)
Deposits [Abstract]
2021	$ 335,433
2022	118,898
2023	114,432
2024	37,169
2025	17,544
Thereafter	997
Total time deposits	$ 624,473

DEPOSITS - Narrative (Details)

DEPOSITS - Narrative (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Deposits [Abstract]
Aggregate amount of time deposits with minimum denomination of $250,000	$ 55.6	$ 91.2

SHORT AND LONG-TERM BORROWING_2

SHORT AND LONG-TERM BORROWINGS - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2015
Debt Type [Line Items]
Short-term borrowings		$ 0	$ 0
Long-term borrowings		53,869,000	67,629,000
Trust preferred securities qualify as Tier 1 capital		23,900,000	29,400,000
Line of Credit | Nicolet Bankshares, Inc
Debt Type [Line Items]
Line of credit with third party bank		10,000,000
Long-term line of credit available		10,000,000
Long-term line of credit outstanding		$ 0	$ 0
Line of Credit | Nicolet Bankshares, Inc | Minimum
Debt Type [Line Items]
Floor rate		3.50%	3.25%
Line of Credit | Prime Rate | Nicolet Bankshares, Inc
Debt Type [Line Items]
Basis spread rate		0.25%
Line of Credit | LIBOR | Nicolet Bankshares, Inc
Debt Type [Line Items]
Basis spread rate			2.25%
FHLB advances
Debt Type [Line Items]
Long-term borrowings		$ 29,000,000	$ 25,061,000
Weighted average rate of FHLB advances		0.73%	1.57%
FHLB advances collateralized pledged		$ 272,900,000	$ 273,500,000
Subordinated Notes
Debt Type [Line Items]
Long-term borrowings		$ 0	$ 11,993,000
Aggregate amount of subordinated notes				$ 12,000,000
Term of debt				10 years
Subordinated Borrowing, Interest Rate				5.00%
Paycheck Protection Program Liquidity Facility [Member]
Debt Type [Line Items]
PPPLF funds received	$ 344,000,000

SHORT AND LONG-TERM BORROWING_3

SHORT AND LONG-TERM BORROWINGS - Long-term borrowings (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Long-term borrowings	$ 53,869	$ 67,629
FHLB advances
Debt Instrument [Line Items]
Long-term borrowings	29,000	25,061
Junior subordinated debentures
Debt Instrument [Line Items]
Long-term borrowings	24,869	30,575
Subordinated notes
Debt Instrument [Line Items]
Long-term borrowings	$ 0	$ 11,993

SHORT AND LONG-TERM BORROWING_4

SHORT AND LONG-TERM BORROWINGS - Summary of maturity of notes payable (Details) - FHLB advances $ in Thousands	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
2021	$ 4,000
2022	0
2023	0
2024	0
2025	5,000
Thereafter	20,000
Advances from Federal Home Loan Banks	$ 29,000

SHORT AND LONG-TERM BORROWING_5

SHORT AND LONG-TERM BORROWINGS - Junior Subordinated Debentures (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Carrying Value	$ 53,869,000	$ 67,629,000
2005 Mid-Wisconsin Financial Services, Inc. | LIBOR
Debt Instrument [Line Items]
Basis spread rate	1.43%
Junior subordinated debentures
Debt Instrument [Line Items]
Par	$ 32,063,000
Unamortized discount	(7,194,000)
Carrying Value	24,869,000	30,575,000
Junior subordinated debentures | 2005 Mid-Wisconsin Financial Services, Inc.
Debt Instrument [Line Items]
Par	10,310,000
Unamortized discount	(2,972,000)
Carrying Value	$ 7,338,000	$ 7,138,000
Effective interest rate	1.65%	3.32%
Junior subordinated debentures | 2006 Baylake Corp.
Debt Instrument [Line Items]
Par	$ 16,598,000
Unamortized discount	(3,647,000)
Carrying Value	$ 12,951,000	$ 12,715,000
Effective interest rate	1.59%	3.31%
Junior subordinated debentures | 2006 Baylake Corp. | LIBOR
Debt Instrument [Line Items]
Basis spread rate	1.35%
Junior subordinated debentures | 2004 First Menasha Bancshares, Inc.
Debt Instrument [Line Items]
Par	$ 5,155,000
Unamortized discount	(575,000)
Carrying Value	$ 4,580,000	$ 4,536,000
Effective interest rate	3.02%	4.69%
Junior subordinated debentures | 2004 First Menasha Bancshares, Inc. | LIBOR
Debt Instrument [Line Items]
Basis spread rate	2.79%
Junior subordinated debentures | 2004 Nicolet Bankshares Statutory Trust
Debt Instrument [Line Items]
Par	$ 0
Unamortized discount	0
Carrying Value	$ 0	$ 6,186,000
Stated interest rate		8.00%

EMPLOYEE AND DIRECTOR BENEFIT_2

EMPLOYEE AND DIRECTOR BENEFIT PLANS - Narrative (Details)	12 Months Ended
	Dec. 31, 2020USD ($)Planshares	Dec. 31, 2019USD ($)shares	Dec. 31, 2018USD ($)
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Number of deferred compensation plans | Plan	2
Employee percentage contribution	100.00%
Employer contribution matching percentage	100.00%
Percentage of employee's gross pay	6.00%
Vesting period	5 years
Company 401k expense	$ 2,200,000	$ 2,900,000	$ 1,800,000
Profit sharing contribution	500,000	1,100,000
Deferred compensation plan | Key Management Employees | Other liabilities
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Liability for cumulative employee contributions and earnings	1,500,000	900,000
Non elective contributions to selected recipients	$ 1,400,000	$ 1,800,000
Deferred compensation plan | Director
Deferred Compensation Arrangement with Individual, Share-based Payments [Line Items]
Maximum percentage to defer the compensation under the plan	100.00%
Shares purchased under deferred compensation plan (in shares) | shares	2,561	3,769
Value of shares purchased under deferred compensation plan	$ 149,000	$ 220,000
Value of shares distributed under director plan	$ 20,157	$ 33,000
Shares distributed under director plan (in shares) | shares	282	672
Deferred compensation liability offsetting equity component	$ 1,200,000	$ 1,000,000
Deferred compensation liability offsetting equity component (in shares) | shares	31,481	29,202

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period of options	10 years
Stock based compensation expense	$ 5.3	$ 4.8	$ 4.7
Unrecognized compensation cost	$ 9.7
Remaining vesting period over which cost expected to be recognized	3 years
Stock based compensation tax benefit	$ 0.8	2.3	0.2
2011 Long Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares initially covered under the plan (in shares)	3,000,000
Number of shares were available for grant (in shares)	1,300,000
2002 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares initially covered under the plan (in shares)	1,175,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total intrinsic value of options exercised	$ 2.5	13.9	2.2
Director | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock based compensation expense	$ 0.4	$ 0.3	$ 0.2
Restricted stock grants (in shares)	7,950	4,257	3,510

STOCK-BASED COMPENSATION - Summ

STOCK-BASED COMPENSATION - Summery weighted average assumptions for valuing stock option grants (Details) - Stock Incentive Plan - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	25.00%	25.00%	25.00%
Risk-free interest rate	1.35%	1.75%	2.61%
Expected average life	7 years	7 years	7 years
Weighted average per share fair value of options (in dollars per share)	$ 20.55	$ 21.30	$ 17.36

STOCK-BASED COMPENSATION - Stoc

STOCK-BASED COMPENSATION - Stock option activity (Details) - Stock Options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Weighted Average Exercise Price
Shares surrendered to satisfy exercise price and/or tax withholding requirements	18,952	142,752	6,411
Stock Incentive Plan
Option Shares Outstanding
Outstanding, beginning of period (in shares)	1,443,733	1,581,699	1,643,255
Granted (in shares)	54,500	203,000	15,500
Exercise of stock options (in shares)	(60,773)	(337,428)	(70,556)
Forfeited (in shares)	0	(3,538)	(6,500)
Outstanding, end of period (in shares)	1,437,460	1,443,733	1,581,699
Weighted Average Exercise Price
Outstanding, beginning of period (in dollars per share)	$ 48.75	$ 40.77	$ 39.82
Granted (in dollars per share)	69.44	69.69	52.76
Exercise of stock options (in dollars per share)	26.51	24.15	21.52
Forfeited (in dollars per share)	0	27.43	39.43
Outstanding, end of period (in dollars per share)	$ 50.47	$ 48.75	$ 40.77
Exercisable (in shares)	800,310
Exercisable (in dollars per share)	$ 46.18
Outstanding, Weighted Average Remaining Life (in years)	6 years 7 months 6 days	7 years 4 months 24 days	7 years 4 months 24 days
Exercisable, Weighted Average Remaining Life (in years)	6 years 1 month 6 days
Outstanding, Aggregate Intrinsic Value	$ 23,840	$ 36,428	$ 13,825
Exercisable, Aggregate Intrinsic Value	$ 16,310

STOCK-BASED COMPENSATION - Sche

STOCK-BASED COMPENSATION - Schedule of options outstanding (Details)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding (in shares) | shares	1,437,460
Number of Shares Exercisable (in shares) | shares	800,310
Weighted Average Exercise Price Outstanding (in dollars per share)	$ 50.47
Weighted Average Exercise Price Exercisable (in dollars per share)	$ 46.18
Weighted Average Remaining Life (Years) Outstanding	6 years 7 months 6 days
Weighted Average Remaining Life (Years) Exercisable	6 years 1 month 6 days
Exercise Price $13.73 - $30.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding (in shares) | shares	82,013
Number of Shares Exercisable (in shares) | shares	77,963
Weighted Average Exercise Price Outstanding (in dollars per share)	$ 21.98
Weighted Average Exercise Price Exercisable (in dollars per share)	$ 22.27
Weighted Average Remaining Life (Years) Outstanding	3 years 1 month 6 days
Weighted Average Remaining Life (Years) Exercisable	3 years 2 months 12 days
Exercise Price $30.01 - $40.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding (in shares) | shares	146,297
Number of Shares Exercisable (in shares) | shares	116,197
Weighted Average Exercise Price Outstanding (in dollars per share)	$ 35.82
Weighted Average Exercise Price Exercisable (in dollars per share)	$ 35.52
Weighted Average Remaining Life (Years) Outstanding	5 years 4 months 24 days
Weighted Average Remaining Life (Years) Exercisable	5 years 3 months 18 days
Exercise Price $40.01 - $50.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding (in shares) | shares	801,150
Number of Shares Exercisable (in shares) | shares	478,350
Weighted Average Exercise Price Outstanding (in dollars per share)	$ 48.86
Weighted Average Exercise Price Exercisable (in dollars per share)	$ 48.86
Weighted Average Remaining Life (Years) Outstanding	6 years 4 months 24 days
Weighted Average Remaining Life (Years) Exercisable	6 years 4 months 24 days
Exercise Price $50.01 - $60.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding (in shares) | shares	160,500
Number of Shares Exercisable (in shares) | shares	88,200
Weighted Average Exercise Price Outstanding (in dollars per share)	$ 56.08
Weighted Average Exercise Price Exercisable (in dollars per share)	$ 56.18
Weighted Average Remaining Life (Years) Outstanding	7 years
Weighted Average Remaining Life (Years) Exercisable	6 years 10 months 24 days
Exercise Price $60.01- $73.52
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Shares Outstanding (in shares) | shares	247,500
Number of Shares Exercisable (in shares) | shares	39,600
Weighted Average Exercise Price Outstanding (in dollars per share)	$ 70.16
Weighted Average Exercise Price Exercisable (in dollars per share)	$ 70.01
Weighted Average Remaining Life (Years) Outstanding	8 years 10 months 24 days
Weighted Average Remaining Life (Years) Exercisable	8 years 10 months 24 days
Minimum | Exercise Price $13.73 - $30.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	$ 13.73
Weighted Average Exercise Price Exercisable (in dollars per share)	13.73
Minimum | Exercise Price $30.01 - $40.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	30.01
Weighted Average Exercise Price Exercisable (in dollars per share)	30.01
Minimum | Exercise Price $40.01 - $50.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	40.01
Weighted Average Exercise Price Exercisable (in dollars per share)	40.01
Minimum | Exercise Price $50.01 - $60.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	50.01
Weighted Average Exercise Price Exercisable (in dollars per share)	50.01
Minimum | Exercise Price $60.01- $73.52
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	60.01
Weighted Average Exercise Price Exercisable (in dollars per share)	60.01
Maximum | Exercise Price $13.73 - $30.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	30
Weighted Average Exercise Price Exercisable (in dollars per share)	30
Maximum | Exercise Price $30.01 - $40.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	40
Weighted Average Exercise Price Exercisable (in dollars per share)	40
Maximum | Exercise Price $40.01 - $50.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	50
Weighted Average Exercise Price Exercisable (in dollars per share)	50
Maximum | Exercise Price $50.01 - $60.00
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	60
Weighted Average Exercise Price Exercisable (in dollars per share)	60
Maximum | Exercise Price $60.01- $73.52
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Exercise Price Outstanding (in dollars per share)	73.52
Weighted Average Exercise Price Exercisable (in dollars per share)	$ 73.52

STOCK-BASED COMPENSATION - Rest

STOCK-BASED COMPENSATION - Restricted stock award activity (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Weighted Average Grant Date Fair  Value
Outstanding, beginning of period (in dollars per share)	$ 44.94	$ 39.37	$ 34.26
Granted (in dollars per share)	60.29	67.59	52.55
Vested (in dollars per share)	50.90	51.77	43.58
Forfeited (in dollars per share)	0	16.50	16.50
Outstanding, end of period (in dollars per share)	$ 53.57	$ 44.94	$ 39.37
Shares surrendered to satisfy tax withholding requirements	4,733	4,688	3,948
Stock Incentive Plan
Restricted Shares Outstanding
Outstanding, beginning of period (in shares)	18,925	22,521	29,512	30,920
Granted (in shares)	19,672	12,498	18,256
Vested (in shares)	(23,268)	(19,081)	(19,661)
Forfeited (in shares)	0	(408)	(3)
Outstanding, end of period (in shares)	18,925	22,521	29,512

STOCKHOLDERS' EQUITY (Details)

STOCKHOLDERS' EQUITY (Details) - USD ($) $ / shares in Units, $ in Thousands	Nov. 08, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Transaction [Line Items]
Stock repurchase remaining authorized amount		$ 20,400
Common stock issued in acquisitions		0	$ 79,797	$ 0
Value of cash consideration		21,820
Choice Bancorp Inc.
Stock Transaction [Line Items]
Number of common stock issued for consideration (in shares)	1,184,102
Common stock issued in acquisitions	$ 79,800
Value of cash consideration	1,700
Costs incurred related to stock issuance	$ 200
Common stock repurchase program
Stock Transaction [Line Items]
Stock repurchased under plan		$ 40,500
Number of shares cancelled under plan (in shares)		646,700
Weighted average price of share cancelled (in dollars per share)		$ 62.69

INCOME TAXES - Current and defe

INCOME TAXES - Current and deferred amounts of income tax expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Current	$ 29,764	$ 15,353	$ 14,967
Deferred	(9,288)	1,105	(1,521)
Income tax expense	$ 20,476	$ 16,458	$ 13,446

INCOME TAXES - Income tax recon

INCOME TAXES - Income tax reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Tax on pretax income, less noncontrolling interest, at statutory rates	$ 16,926	$ 14,931	$ 11,441
State income taxes, net of federal effect	5,030	3,672	3,308
Tax-exempt interest income	(527)	(609)	(574)
Non-deductible interest disallowance	14	29	30
Increase in cash surrender value life insurance	(738)	(573)	(508)
Non-deductible business entertainment	170	189	156
Stock-based employee compensation	(839)	(2,347)	(232)
Non-deductible compensation	272	3,122	0
Sale of UFS	(109)	(2,176)	0
Other, net	277	220	(175)
Income tax expense	$ 20,476	$ 16,458	$ 13,446

INCOME TAXES - Net deferred tax

INCOME TAXES - Net deferred tax asset (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
ACL-Loans	$ 9,328	$ 4,985
Net operating loss carryforwards	1,692	1,808
Credit carryforwards	0	43
Compensation	5,822	3,477
Purchase of noncontrolling interest	2,112	0
Other	2,949	2,830
Other real estate	538	201
Total deferred tax assets	22,441	13,344
Deferred tax liabilities:
Premises and equipment	(1,577)	(1,390)
Prepaid expenses	(1,010)	(778)
Investment securities	(451)	(755)
Core deposit and other intangibles	(1,777)	(2,836)
Purchase accounting adjustments to liabilities	(1,969)	(2,375)
MSR asset	(2,269)	(1,391)
Other	(282)	0
Unrealized gain on securities AFS	(4,959)	(1,879)
Total deferred tax liabilities	(14,294)	(11,404)
Net deferred tax assets	$ 8,147	$ 1,940

INCOME TAXES - Narrative (Detai

INCOME TAXES - Narrative (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Additional Tax information [Line Items]
Valuation allowance	$ 0	$ 0
Federal
Additional Tax information [Line Items]
Operating loss carryforwards	3,300,000
State
Additional Tax information [Line Items]
Operating loss carryforwards	$ 15,700,000

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Contract or notional amount of exposure to off-balance-sheet risk (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Commitments to extend credit
Other Commitments [Line Items]
Contract and notional amounts of commitments	$ 950,287	$ 773,555
Financial standby letters of credit
Other Commitments [Line Items]
Contract and notional amounts of commitments	8,241	10,730
Performance standby letters of credit
Other Commitments [Line Items]
Contract and notional amounts of commitments	$ 8,366	$ 8,469

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Derivative fair value, net	$ (0.2)	$ 0.1
Commercial-related commitments to extend credit	78.00%	74.00%
Federal funds accommodations	$ 175	$ 175
Interest Rate Lock Commitments
Derivative [Line Items]
Commitments to sell residential mortgage loans held for sale considered derivative instruments	113	43
Forward Commitments
Derivative [Line Items]
Commitments to sell residential mortgage loans held for sale considered derivative instruments	$ 20	$ 16

RELATED PARTY TRANSACTIONS (Det

RELATED PARTY TRANSACTIONS (Details) - USD ($)	3 Months Ended		9 Months Ended	12 Months Ended			24 Months Ended
	Dec. 31, 2020	Mar. 31, 2019	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Related Party Transaction [Line Items]
Related party loans, total	$ 89,000,000			$ 89,000,000	$ 86,000,000		$ 89,000,000
Purchase of noncontrolling interest				$ 8,000,000	$ 0	$ 0
Nicolet Joint Ventures, LLC (the "JV")
Related Party Transaction [Line Items]
Ownership percentage by noncontrolling owners			50.00%
Noncontrolling interest, ownership percentage purchased	50.00%
Purchase of noncontrolling interest	$ 8,000,000
Chief Executive Officer
Related Party Transaction [Line Items]
Stock repurchased (in shares)				5,851	32,415
Cumulative amount repurchased				$ 400,000	$ 2,200,000
Average cost per share (in dollars per share)				$ 71.45	$ 69.21
Director
Related Party Transaction [Line Items]
Stock repurchased (in shares)				5,852	33,993
Cumulative amount repurchased				$ 400,000	$ 2,200,000
Average cost per share (in dollars per share)				$ 71.45	$ 64.02
Director | New branch location in facility opened in October 2013
Related Party Transaction [Line Items]
Rent expense				$ 122,000	$ 112,000	100,000
Director | 2019 branch reconstruction
Related Party Transaction [Line Items]
Payments for branch reconstruction				$ 900,000	400,000		$ 1,300,000
Percentage payments for branch reconstruction paid to subcontractor				75.00%
Director | 2018 branch reconstruction
Related Party Transaction [Line Items]
Payments for branch reconstruction					$ 1,000,000
Percentage payments for branch reconstruction paid to subcontractor					75.00%
Nicolet Joint Ventures, LLC (the "JV") | Nicolet national bank
Related Party Transaction [Line Items]
Rent expense			$ 1,300,000		$ 1,200,000	1,100,000
Management | Lease agreement for a non-branch location owned by a relative of a senior management team member and paid approximately
Related Party Transaction [Line Items]
Lease payments		$ 47,500				$ 138,000

ASSETS GAINS (LOSSES), NET - Co

ASSETS GAINS (LOSSES), NET - Components of net gain (loss) on assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets Gains (Losses), Net [Abstract]
Gains (losses) on sales of securities AFS, net	$ 395	$ (22)	$ (212)
Gains (losses) on equity securities, net	(987)	1,115	77
Gains (losses) on sales of OREO, net	157	(88)	1,032
Write-downs of OREO	(1,040)	(300)	(120)
Write-down of other investment	(100)	(100)	0
Gains (losses) on sales of other investments, net	0	7,442	187
Gains (losses) on sales or dispositions of other assets, net	(230)	(150)	205
Asset gains (losses), net	$ (1,805)	$ 7,897	$ 1,169

REGULATORY CAPITAL REQUIREMEN_3

REGULATORY CAPITAL REQUIREMENTS - Company's and Bank's actual regulatory capital amounts and ratios (Details) $ in Thousands	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Allowable amount of dividends before regulatory approval required	$ 11,000
Nicolet Bankshares, Inc
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital, Actual amount	$ 406,325	$ 404,573
Total risk-based capital, Actual ratio	0.129	0.134
Total risk-based capital, For capital adequacy purposes, Amount	$ 252,683	$ 241,333
Total risk-based capital, For capital adequacy purposes, Ratio	0.080	0.080
Tier I risk-based capital, Actual amount	$ 385,068	$ 378,608
Tier I risk-based capital, Actual ratio	0.122	0.126
Tier I risk-based capital, For capital adequacy purposes, Amount	$ 189,512	$ 181,000
Tier I risk-based capital, For capital adequacy purposes, Ratio	0.060	0.060
Common equity Tier 1 capital, Actual Amount	$ 361,162	$ 348,454
Common equity Tier 1 capital, Actual Ratio	0.114	0.116
Common equity Tier 1 capital, For Capital Adequacy Purposes, Amount	$ 142,134	$ 135,750
Common equity Tier 1 capital, For Capital Adequacy Purposes, Ratio	4.50%	4.50%
Leverage, Actual amount	$ 385,068	$ 378,608
Leverage, Actual ratio	0.090	0.119
Leverage, For capital adequacy purposes, Amount	$ 170,402	$ 127,036
Leverage, For capital adequacy purposes, Ratio	0.040	0.040
Nicolet national bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total risk-based capital, Actual amount	$ 351,081	$ 323,432
Total risk-based capital, Actual ratio	0.112	0.108
Total risk-based capital, For capital adequacy purposes, Amount	$ 251,769	$ 240,551
Total risk-based capital, For capital adequacy purposes, Ratio	0.080	0.080
Total risk-based capital, To be well capitalized under prompt corrective action provisions, Amount	$ 314,711	$ 300,688
Total risk-based capital, To be well capitalized under prompt corrective action provisions, Ratio	0.100	0.100
Tier I risk-based capital, Actual amount	$ 329,824	$ 309,460
Tier I risk-based capital, Actual ratio	0.105	0.103
Tier I risk-based capital, For capital adequacy purposes, Amount	$ 188,826	$ 180,413
Tier I risk-based capital, For capital adequacy purposes, Ratio	0.060	0.060
Tier I risk-based capital, To be well capitalized under prompt corrective action provisions, Amount	$ 251,769	$ 240,551
Tier I risk-based capital, To be well capitalized under prompt corrective action provisions, Ratio	0.080	0.080
Common equity Tier 1 capital, Actual Amount	$ 329,824	$ 309,460
Common equity Tier 1 capital, Actual Ratio	0.105	0.103
Common equity Tier 1 capital, For Capital Adequacy Purposes, Amount	$ 141,620	$ 135,310
Common equity Tier 1 capital, For Capital Adequacy Purposes, Ratio	4.50%	4.50%
Common equity Tier 1 capital, To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 204,562	$ 195,447
Common equity Tier 1 capital, To be well capitalized under prompt corrective action provisions ratio, Ratio	6.50%	6.50%
Leverage, Actual amount	$ 329,824	$ 309,460
Leverage, Actual ratio	0.078	0.098
Leverage, For capital adequacy purposes, Amount	$ 170,025	$ 126,660
Leverage, For capital adequacy purposes, Ratio	0.040	0.040
Leverage, To be well capitalized under prompt corrective action provisions, Amount	$ 212,532	$ 158,325
Leverage, To be well capitalized under prompt corrective action provisions, Ratio	0.050	0.050

FAIR VALUE MEASUREMENTS - Measu

FAIR VALUE MEASUREMENTS - Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	$ 539,337	$ 449,302
Measured at Fair Value on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	539,337	449,302
Measured at Fair Value on a Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
Measured at Fair Value on a Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	536,207	446,172
Measured at Fair Value on a Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	3,130	3,130
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	63,451	16,460
U.S. government agency securities | Measured at Fair Value on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	63,451	16,460
U.S. government agency securities | Measured at Fair Value on a Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
U.S. government agency securities | Measured at Fair Value on a Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	63,451	16,460
U.S. government agency securities | Measured at Fair Value on a Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
State, county and municipals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	231,868	156,393
State, county and municipals | Measured at Fair Value on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	231,868	156,393
State, county and municipals | Measured at Fair Value on a Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
State, county and municipals | Measured at Fair Value on a Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	231,868	156,393
State, county and municipals | Measured at Fair Value on a Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	162,495	195,018
Mortgage-backed securities | Measured at Fair Value on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	162,495	195,018
Mortgage-backed securities | Measured at Fair Value on a Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
Mortgage-backed securities | Measured at Fair Value on a Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	162,495	195,018
Mortgage-backed securities | Measured at Fair Value on a Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	81,523	81,431
Corporate debt securities | Measured at Fair Value on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	81,523	81,431
Corporate debt securities | Measured at Fair Value on a Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	0	0
Corporate debt securities | Measured at Fair Value on a Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	78,393	78,301
Corporate debt securities | Measured at Fair Value on a Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities AFS	3,130	3,130
Equity securities | Measured at Fair Value on a Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	3,567	3,375
Equity securities | Measured at Fair Value on a Recurring Basis | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	3,567	3,375
Equity securities | Measured at Fair Value on a Recurring Basis | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	0	0
Equity securities | Measured at Fair Value on a Recurring Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Chang

FAIR VALUE MEASUREMENTS - Changes in Level 3 assets (Details) - Level 3 - Measured at Fair Value on a Recurring Basis - Securities AFS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Level 3 Fair Value Measurements:
Balance at beginning of year	$ 3,130	$ 8,490
Acquired balances	0	300
Paydowns/Sales/Settlements	0	(5,660)
Balance at end of year	$ 3,130	$ 3,130

FAIR VALUE MEASUREMENTS - Fair

FAIR VALUE MEASUREMENTS - Fair value on a nonrecurring basis (Details) - Measured at Fair Value on a Nonrecurring Basis - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Collateral dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 7,633
OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	3,608	$ 1,000
MSR asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	9,276	8,420
Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure		16,150
Level 1 | Collateral dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	0
Level 1 | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	0	0
Level 1 | MSR asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	0	0
Level 1 | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure		0
Level 2 | Collateral dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	0
Level 2 | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	0	0
Level 2 | MSR asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	0	0
Level 2 | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure		0
Level 3 | Collateral dependent loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	7,633
Level 3 | OREO
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	3,608	1,000
Level 3 | MSR asset
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure	$ 9,276	8,420
Level 3 | Impaired loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure		$ 16,150

FAIR VALUE MEASUREMENTS - Carry

FAIR VALUE MEASUREMENTS - Carrying amounts and estimated fair values of financial instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Financial assets:
Securities AFS	$ 539,337	$ 449,302
Carrying Amount
Financial assets:
Cash and cash equivalents	802,859	182,059
Certificates of deposit in other banks	29,521	19,305
Securities AFS	539,337	449,302
Other investments	27,619	24,072
Loans held for sale	21,450	2,706
Loans, net	2,756,928	2,559,779
BOLI	83,262	78,140
MSR asset	9,230	5,919
Financial liabilities:
Deposits	3,910,399	2,954,453
Long-term borrowings	53,869	67,629
Estimated Fair Value
Financial assets:
Cash and cash equivalents	802,859	182,059
Certificates of deposit in other banks	31,053	19,310
Securities AFS	539,337	449,302
Other investments	27,619	24,072
Loans held for sale	22,329	2,753
Loans, net	2,834,452	2,593,110
BOLI	83,262	78,140
MSR asset	9,276	8,420
Financial liabilities:
Deposits	3,917,121	2,956,229
Long-term borrowings	53,859	66,816
Level 1 | Estimated Fair Value
Financial assets:
Cash and cash equivalents	802,859	182,059
Certificates of deposit in other banks	0	0
Securities AFS	0	0
Other investments	3,567	3,375
Loans held for sale	0	0
Loans, net	0	0
BOLI	83,262	78,140
MSR asset	0	0
Financial liabilities:
Deposits	0	0
Long-term borrowings	0	0
Level 2 | Estimated Fair Value
Financial assets:
Cash and cash equivalents	0	0
Certificates of deposit in other banks	31,053	19,310
Securities AFS	536,207	446,172
Other investments	20,155	16,759
Loans held for sale	22,329	2,753
Loans, net	0	0
BOLI	0	0
MSR asset	0	0
Financial liabilities:
Deposits	0	0
Long-term borrowings	29,488	25,075
Level 3 | Estimated Fair Value
Financial assets:
Cash and cash equivalents	0	0
Certificates of deposit in other banks	0	0
Securities AFS	3,130	3,130
Other investments	3,897	3,938
Loans held for sale	0	0
Loans, net	2,834,452	2,593,110
BOLI	0	0
MSR asset	9,276	8,420
Financial liabilities:
Deposits	3,917,121	2,956,229
Long-term borrowings	$ 24,371	$ 41,741

PARENT COMPANY ONLY FINANCIAL_3

PARENT COMPANY ONLY FINANCIAL INFORMATION - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Cash and due from subsidiary	$ 88,460	$ 75,433
Goodwill	163,151	151,198	$ 107,366
Total assets	4,551,789	3,577,260
Liabilities and Stockholders’ Equity
Other liabilities	48,332	38,188
Stockholders’ equity	539,189	516,262
Total liabilities, noncontrolling interest and stockholders’ equity	4,551,789	3,577,260
Nicolet Bankshares, Inc
Assets
Cash and due from subsidiary	49,998	70,426
Investments	6,742	6,650
Investments in subsidiaries	513,736	487,644
Goodwill	(3,266)	(3,266)
Other assets	177	396
Total assets	567,387	561,850
Liabilities and Stockholders’ Equity
Junior subordinated debentures	24,869	30,575
Subordinated notes	0	11,993
Other liabilities	3,329	3,020
Stockholders’ equity	539,189	516,262
Total liabilities, noncontrolling interest and stockholders’ equity	$ 567,387	$ 561,850

PARENT COMPANY ONLY FINANCIAL_4

PARENT COMPANY ONLY FINANCIAL INFORMATION - Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Interest income	$ 149,202	$ 138,588	$ 125,537
Interest expense	19,864	22,510	18,889
Net interest income	129,338	116,078	106,648
Income tax benefit	(20,476)	(16,458)	(13,446)
Net income	60,469	54,988	41,353
Nicolet Bankshares, Inc
Condensed Financial Statements, Captions [Line Items]
Interest income	39	55	52
Interest expense	2,313	2,936	2,844
Net interest income	(2,274)	(2,881)	(2,792)
Dividend income from subsidiaries	60,215	50,363	40,775
Operating expense	(886)	(321)	(364)
Gain (loss) on investments, net	(1,087)	1,015	265
Income tax benefit	1,102	506	305
Earnings before equity in undistributed income (loss) of subsidiaries	57,070	48,682	38,189
Equity in undistributed income (loss) of subsidiaries	3,052	5,959	2,847
Net income	$ 60,122	$ 54,641	$ 41,036

PARENT COMPANY ONLY FINANCIAL_5

PARENT COMPANY ONLY FINANCIAL INFORMATION - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows From Operating Activities:
Net income attributable to Nicolet Bankshares, Inc.	$ 60,469	$ 54,988	$ 41,353
Cash Flows From Financing Activities:
Purchase and retirement of common stock	(42,088)	(28,460)	(22,749)
Proceeds from issuance of common stock, net	2,055	8,742	1,800
Repayments of long-term borrowings	(384,091)	(87,237)	(1,253)
Nicolet Bankshares, Inc
Cash Flows From Operating Activities:
Net income attributable to Nicolet Bankshares, Inc.	60,122	54,641	41,036
Adjustments to reconcile net income to net cash provided by operating activities:
Accretion of discounts	486	515	515
(Gain) loss on investments, net	1,087	(1,015)	(265)
Change in other assets and liabilities, net	1,786	(421)	(25)
Equity in undistributed (income) loss of subsidiaries, net of dividends	(3,052)	(5,959)	(2,847)
Net cash provided by operating activities	60,429	47,761	38,414
Cash Flows From Investing Activities:
Proceeds from sale of investments	185	0	708
Purchases of investments	(1,179)	(2,484)	(920)
Net cash paid in business combinations	(21,644)	(412)	0
Net cash used in investing activities	(22,638)	(2,896)	(212)
Cash Flows From Financing Activities:
Purchase and retirement of common stock	(42,088)	(28,460)	(22,749)
Proceeds from issuance of common stock, net	2,055	8,742	1,800
Repayments of long-term borrowings	(18,186)	0	0
Net cash used in financing activities	(58,219)	(19,718)	(20,949)
Net increase (decrease) in cash and due from subsidiary	(20,428)	25,147	17,253
Beginning cash and due from subsidiary	70,426	45,279	28,026
Ending cash and due from subsidiary	$ 49,998	$ 70,426	$ 45,279

EARNINGS PER COMMON SHARE - Cal

EARNINGS PER COMMON SHARE - Calculations for basic and diluted earnings per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Net income attributable to Nicolet Bankshares, Inc.	$ 60,122	$ 54,641	$ 41,036
Weighted average common shares outstanding (in shares)	10,337,138	9,561,978	9,640,258
Effect of dilutive common stock awards (in shares)	204,000	338,000	316,000
Diluted weighted average common shares outstanding (in shares)	10,541,251	9,900,319	9,956,353
Basic earnings per common share (in dollars per share)	$ 5.82	$ 5.71	$ 4.26
Diluted earnings per common share (in dollars per share)	$ 5.70	$ 5.52	$ 4.12

EARNINGS PER COMMON SHARE - Nar

EARNINGS PER COMMON SHARE - Narrative (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share [Abstract]
Shares excluded from calculation of earnings per common share (in shares)	0.1	0.1	0.1