Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Loans, including loan fees	$ 125,524	$ 113,953	$ 100,541
Investment securities:
Taxable	7,584	6,068	4,728
Tax-exempt	2,075	2,296	2,360
Other interest income	3,405	3,220	1,624
Total interest income	138,588	125,537	109,253
Interest expense:
Deposits	18,965	15,420	7,686
Short-term borrowings	5	9	84
Long-term borrowings	3,540	3,460	2,741
Total interest expense	22,510	18,889	10,511
Net interest income	116,078	106,648	98,742
Provision for loan losses	1,200	1,600	2,325
Net interest income after provision for loan losses	114,878	105,048	96,417
Noninterest income:
Mortgage income, net	11,878	6,344	5,361
BOLI income	2,369	2,418	1,778
Asset gains (losses), net	7,897	1,169	2,029
Other income	5,559	5,528	4,454
Total noninterest income	53,367	39,509	34,639
Noninterest expense:
Personnel	54,437	49,476	44,458
Occupancy, equipment and office	14,788	14,574	13,308
Business development and marketing	5,685	5,324	4,700
Data processing	9,950	9,514	8,715
Intangibles amortization	3,872	4,389	4,695
Other expense	8,067	6,481	5,480
Total noninterest expense	96,799	89,758	81,356
Income before income tax expense	71,446	54,799	49,700
Income tax expense	16,458	13,446	16,267
Net income	54,988	41,353	33,433
Less: Net income attributable to noncontrolling interest	347	317	283
Net income attributable to Nicolet Bankshares, Inc.	$ 54,641	$ 41,036	$ 33,150
Earnings per common share:
Basic (in dollars per share)	$ 5.71	$ 4.26	$ 3.51
Diluted (in dollars per share)	$ 5.52	$ 4.12	$ 3.33
Weighted average common shares outstanding:
Basic (in shares)	9,561,978	9,640,258	9,439,951
Diluted (in shares)	9,900,319	9,956,353	9,958,160
Trust services fee income
Noninterest income:
Fees and commisions	$ 6,227	$ 6,498	$ 6,031
Brokerage fee income
Noninterest income:
Fees and commisions	8,115	7,042	5,736
Service charges on deposit accounts
Noninterest income:
Fees and commisions	4,824	4,845	4,604
Card interchange income
Noninterest income:
Fees and commisions	$ 6,498	$ 5,665	$ 4,646