PARENT COMPANY ONLY FINANCIAL INFORMATION - Statements of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Interest income	$ 171,559	$ 149,202	$ 138,588
Interest expense	13,604	19,864	22,510
Net interest income	157,955	129,338	116,078
Income tax benefit	(20,470)	(20,476)	(16,458)
Net income	60,652	60,469	54,988
Nicolet Bankshares, Inc
Condensed Financial Statements, Captions [Line Items]
Interest income	18	39	55
Interest expense	2,959	2,313	2,936
Net interest income	(2,941)	(2,274)	(2,881)
Dividend income from subsidiaries	65,000	60,215	50,363
Operating expense	(2,562)	(886)	(321)
Gain (loss) on investments, net	3,995	(1,087)	1,015
Income tax benefit	437	1,102	506
Earnings before equity in undistributed income (loss) of subsidiaries	63,929	57,070	48,682
Equity in undistributed income (loss) of subsidiaries	(3,277)	3,052	5,959
Net income	$ 60,652	$ 60,122	$ 54,641