Represents percentage of allowance for credit losses.

No definition available.

Name:	nic_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossToTotalPercent
Namespace Prefix:	nic_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, excluding accrued interest, of increase in allowance for credit loss on financing receivable from recovery. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, excluding accrued interest, of decrease (increase) in allowance for credit loss on financing receivable from writeoff (recovery). Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoffAfterRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476148/220-40-50-22

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LienCategoryAxis=nic_FirstLienMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LienCategoryAxis=us-gaap_JuniorLienMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nic_CommercialAndIndustrialFinancingReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nic_CommercialRealEstateOwnerOccupiedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nic_AgriculturalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nic_ConstructionAndLandDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=nic_RetailAndOtherFinancingReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans, Allowance for Credit Losses - Loans, and Credit Quality - Schedule of Activity in ACL - Loans by Portfolio Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
ACL-Loans
Beginning balance	$ 67,480	$ 64,347	$ 66,322	$ 63,610	$ 63,610
Provision for credit losses			2,800		3,750
Charge-offs	(568)	(375)	(956)	(591)	(1,493)
Recoveries	196	92	242	295	455
Net (charge-offs) recoveries	(372)	(283)	(714)	(296)	(1,038)
Ending balance	68,408	$ 65,414	$ 68,408	65,414	$ 66,322
As % of ACL-Loans			100.00%		100.00%
Residential first mortgage
ACL-Loans
Charge-offs			$ (13)		$ 0
Residential junior mortgage
ACL-Loans
Charge-offs			(2)		0
Commercial & industrial
ACL-Loans
Charge-offs			(598)		(918)
Owner-occupied CRE
ACL-Loans
Charge-offs			(189)		(120)
Agricultural
ACL-Loans
Charge-offs			(65)		0
CRE investment
ACL-Loans
Charge-offs			0		0
Construction & land development
ACL-Loans
Charge-offs			0		0
Residential construction
ACL-Loans
Charge-offs			0		0
Retail & other
ACL-Loans
Beginning balance			931	1,207	1,207
Provision for credit losses			(250)		61
Charge-offs			(89)		(455)
Recoveries			52		118
Net (charge-offs) recoveries			(37)		(337)
Ending balance	644		$ 644		$ 931
As % of ACL-Loans			1.00%		2.00%
Commercial \| Commercial & industrial
ACL-Loans
Beginning balance			$ 16,147	15,225	$ 15,225
Provision for credit losses			1,488		1,789
Charge-offs			(598)		(918)
Recoveries			154		51
Net (charge-offs) recoveries			(444)		(867)
Ending balance	17,191		$ 17,191		$ 16,147
As % of ACL-Loans			25.00%		24.00%
Commercial \| Owner-occupied CRE
ACL-Loans
Beginning balance			$ 5,362	9,082	$ 9,082
Provision for credit losses			204		(3,844)
Charge-offs			(189)		(120)
Recoveries			35		244
Net (charge-offs) recoveries			(154)		124
Ending balance	5,412		$ 5,412		$ 5,362
As % of ACL-Loans			8.00%		8.00%
Commercial \| Agricultural
ACL-Loans
Beginning balance			$ 9,957	12,629	$ 12,629
Provision for credit losses			244		(2,672)
Charge-offs			(65)		0
Recoveries			0		0
Net (charge-offs) recoveries			(65)		0
Ending balance	10,136		$ 10,136		$ 9,957
As % of ACL-Loans			15.00%		15.00%
Commercial real estate \| CRE investment
ACL-Loans
Beginning balance			$ 14,616	12,693	$ 12,693
Provision for credit losses			316		1,923
Charge-offs			0		0
Recoveries			0		0
Net (charge-offs) recoveries			0		0
Ending balance	14,932		$ 14,932		$ 14,616
As % of ACL-Loans			22.00%		22.00%
Commercial real estate \| Construction & land development
ACL-Loans
Beginning balance			$ 2,658	2,440	$ 2,440
Provision for credit losses			570		218
Charge-offs			0		0
Recoveries			0		0
Net (charge-offs) recoveries			0		0
Ending balance	3,228		$ 3,228		$ 2,658
As % of ACL-Loans			5.00%		4.00%
Residential \| Residential first mortgage
ACL-Loans
Beginning balance			$ 12,590	7,320	$ 7,320
Provision for credit losses			92		5,237
Charge-offs			(13)		0
Recoveries			0		33
Net (charge-offs) recoveries			(13)		33
Ending balance	12,669		$ 12,669		$ 12,590
As % of ACL-Loans			18.00%		19.00%
Residential \| Residential junior mortgage
ACL-Loans
Beginning balance			$ 2,827	2,098	$ 2,098
Provision for credit losses			239		720
Charge-offs			(2)		0
Recoveries			1		9
Net (charge-offs) recoveries			(1)		9
Ending balance	3,065		$ 3,065		$ 2,827
As % of ACL-Loans			4.00%		4.00%
Residential \| Residential construction
ACL-Loans
Beginning balance			$ 1,234	$ 916	$ 916
Provision for credit losses			(103)		318
Charge-offs			0		0
Recoveries			0		0
Net (charge-offs) recoveries			0		0
Ending balance	$ 1,131		$ 1,131		$ 1,234
As % of ACL-Loans			2.00%		2.00%