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