PARENT COMPANY ONLY FINANCIAL INFORMATION - Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash Flows From Operating Activities:
Net income attributable to Nicolet Bankshares, Inc.	$ 60,652	$ 60,469	$ 54,988
Cash Flows From Investing Activities:
Net cash paid in business combinations	367,797	(21,820)	7,331
Cash Flows From Financing Activities:
Purchase and retirement of common stock	(62,583)	(42,088)	(28,460)
Proceeds from issuance of common stock, net	2,382	2,055	8,742
Capitalized issuance costs, net	(789)		(163)
Repayments of long-term borrowings	(187,961)	(384,091)	(87,237)
Nicolet Bankshares, Inc
Cash Flows From Operating Activities:
Net income attributable to Nicolet Bankshares, Inc.	60,652	60,122	54,641
Adjustments to reconcile net income to net cash provided by operating activities:
Accretion of discounts on borrowings	584	486	515
(Gain) loss on investments, net	(3,995)	1,087	(1,015)
Change in other assets and liabilities, net	1,013	1,786	(421)
Equity in undistributed (income) loss of subsidiaries, net of dividends	3,277	(3,052)	(5,959)
Net cash provided by operating activities	61,531	60,429	47,761
Cash Flows From Investing Activities:
Proceeds from sale of investments	4,105	185	0
Purchases of investments	(5,049)	(1,179)	(2,484)
Net cash paid in business combinations	(63,892)	(21,644)	(412)
Net cash used in investing activities	(64,836)	(22,638)	(2,896)
Cash Flows From Financing Activities:
Purchase and retirement of common stock	(62,583)	(42,088)	(28,460)
Proceeds from issuance of common stock, net	2,382	2,055	8,742
Capitalized issuance costs, net	(789)	0	0
Repayments of long-term borrowings	0	(18,186)	0
Proceeds from issuance of subordinated notes, net	98,953	0	0
Net cash provided by (used in) financing activities	37,963	(58,219)	(19,718)
Net increase (decrease) in cash and due from subsidiary	34,658	(20,428)	25,147
Beginning cash and due from subsidiary	49,998	70,426	45,279
Ending cash and due from subsidiary	$ 84,656	$ 49,998	$ 70,426