Description of Plan (Details) - EBP 002	12 Months Ended
Dec. 31, 2025 USD ($) loan vote hour	Dec. 31, 2024 USD ($)
EBP, Description of Plan [Line Items]
Required service period	90 days
Matching contribution (as a percent)	100.00%
Participant compensation matched (as a percent)	4.00%
Required service hours \| hour	1,000
Employer contributions	$ 4,948,067	$ 4,741,663
Employer contribution, vesting service period	6 years
Employer contribution, vesting percentage	20.00%
Minimum borrowing amount	$ 1,000
Maximum borrowing to total account (as a percent)	50.00%
Maximum borrowing amount	$ 50,000
Basis spread on variable rate (as a percent)	1.00%
Maximum borrowing term	5 years
Number of eligible loans for each participant at a time \| loan	2
Forfeitures used to offset Bank contributions	$ 0	0
Forfeitures used to offset Plan expenses	$ 0	0
Number of votes each participant is entitled to \| vote	1
Dividend payment to participants	$ 501,863	561,271
Participant contribution, rollover	$ 8,478,730	2,492,329
Minimum
EBP, Description of Plan [Line Items]
Loans to participants, interest rate	3.25%
Maximum
EBP, Description of Plan [Line Items]
Loans to participants, interest rate	9.50%
Discretionary Contribution
EBP, Description of Plan [Line Items]
Employer contributions	$ 0	$ 0

EBP, Dividend Payment To Participant

No definition available.

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Namespace Prefix:	nwbi_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

EBP, Employer Contribution, Requisite Service Hours

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Company contribution and/ or investment earning percentage vesting to the participant in Company Matching Contributions, Fixed Rate Contributions, Discretionary Profit-Sharing Contributions, Qualified Non-Elective Contributions, and Disability Contributions, upon completion of minimum service period or attainment of maximum vesting age

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum Vesting service period for company contribution and/ or investment earning to the participant in Company Matching Contributions, Fixed Rate Contributions, Discretionary Profit-Sharing Contributions, Qualified Non-Elective Contributions, and Disability Contributions.

+ References

No definition available.

+ Details

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Namespace Prefix:	nwbi_
Data Type:	xbrli:durationItemType
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- Definition

EBP, Note Receivable From Participant, General Loan, Maximum Borrowing Term

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

EBP, Note Receivable From Participant, Number Of Eligible Loans

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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Period Type:	instant

- Definition

EBP, Participant Loan, Basis Spread On Variable Rate

+ References

No definition available.

+ Details

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Namespace Prefix:	nwbi_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

EBP, Participant Voting Rights, Number

+ References

No definition available.

+ Details

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Namespace Prefix:	nwbi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

EBP, Requisite Service Period

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount of increase in net asset available for benefit from cash contribution from employer of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase in net asset available for benefit from contribution transferred from another qualified plan or from individual retirement account of participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Excludes contribution for participant transmitted by employer of participant in EBP.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478873/962-325-55-17

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(4)(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(4)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 4: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 962
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule III))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

Reference 5: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 962
-SubTopic 325
-Name Accounting Standards Codification
-Section 50
-Paragraph 2B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477783/962-325-50-2B

Reference 6: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477063/962-205-45-7

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

+ Details

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Data Type:	xbrli:stringItemType
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Period Type:	duration

- Definition

Percentage of employer matching contribution on eligible participant contribution to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Namespace Prefix:	us-gaap-ebp_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of participant compensation eligible for employer matching contribution for participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from administrative expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (j)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478416/962-205-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-04(5)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	duration

- Definition

Amount of decrease in forfeited nonvested account of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from employer contribution.

+ References

+ Details

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Namespace Prefix:	us-gaap-ebp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of maximum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow to total participant account balance.

+ References

+ Details

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Period Type:	instant

- Definition

Amount of minimum account balance that participant in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) can borrow.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Interest rate on participant loan in schedule of asset held for investment of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Employee Retirement Income Security Act of 1974
-Number 2520
-Section 103
-Subsection 10
-Paragraph b
-Subparagraph (1)(i)(D)
-Publisher DOL-EBSA

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 962
-SubTopic 205
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6A-05(a)(Schedule I))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477804/962-205-S99-1

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Balance Type:	na
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- Details

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- Details

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- Details

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