Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2019		Dec. 31, 2018
Assets
Cash and due from banks	$ 88,371		$ 85,896
Interest-earning deposits	55,598		163,630
Cash and cash equivalents	143,969	[1]	249,526
Certificates of deposit in other banks	5,395		993
Securities available for sale (“AFS”), at fair value	419,300		400,144
Other investments	20,697		17,997
Loans held for sale	10,564		1,639
Loans	2,242,931		2,166,181
Allowance for loan losses (ALLL)	(13,620)		(13,153)
Loans, net	2,229,311		2,153,028
Premises and equipment, net	47,680		48,173
Bank owned life insurance (“BOLI”)	71,796		66,310
Goodwill and other intangibles, net	121,371		124,307
Accrued interest receivable and other assets	35,588		34,418
Total assets	3,105,671		3,096,535
Deposits
Noninterest-bearing demand deposits	782,968		753,065
Interest-bearing deposits	1,801,479		1,861,073
Total deposits	2,584,447		2,614,138
Long-term borrowings	57,495		77,305
Accrued interest payable and other liabilities	34,987		17,740
Total liabilities	2,676,929		2,709,183
Stockholders' Equity Attributable to Parent [Abstract]
Common stock	94		95
Additional paid-in capital	236,534		247,790
Retained earnings	186,710		144,364
Accumulated other comprehensive income (loss)	4,676		(5,640)
Total Nicolet Bankshares, Inc. stockholders’ equity	428,014		386,609
Noncontrolling interest	728		743
Total stockholders’ equity and noncontrolling interest	428,742		387,352
Total liabilities, noncontrolling interest and stockholders’ equity	$ 3,105,671		$ 3,096,535
Stockholders' Equity, Number of Shares, Par Value and Other Disclosures [Abstract]
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)	9,363,407		9,495,265
Common shares issued (in shares)	9,387,096		9,524,777

[1] * Cash and cash equivalents include restricted cash of $6.3 million and $7.4 million at September 30, 2019 and 2018, respectively, for the reserve balance required with the Federal Reserve Bank. At September 30, 2019, cash and cash equivalents also includes restricted cash of $1.3 million pledged as collateral on interest rate swaps.