Borrowings - Schedule of Capital Debt Securities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Junior subordinated debentures	$ 130,093	$ 129,834
Trust Preferred Securities Subject to Mandatory Redemption
Debt Instrument [Line Items]
Capital debt securities	128,875
Junior subordinated debentures	$ 130,093	129,834
Trust Preferred Securities Subject to Mandatory Redemption \| Northwest Bancorp Capital Trust III
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.38%
Capital debt securities	$ 50,000
Junior subordinated debentures	$ 51,547	51,547
Trust Preferred Securities Subject to Mandatory Redemption \| Northwest Bancorp Statutory Trust IV
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.38%
Capital debt securities	$ 50,000
Junior subordinated debentures	$ 51,547	51,547
Trust Preferred Securities Subject to Mandatory Redemption \| LNB Trust II
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.48%
Capital debt securities	$ 7,875
Junior subordinated debentures	$ 8,119	8,119
Trust Preferred Securities Subject to Mandatory Redemption \| Union National Capital Trust I
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.85%
Capital debt securities	$ 8,000
Junior subordinated debentures	$ 8,049	8,024
Trust Preferred Securities Subject to Mandatory Redemption \| Union National Capital Trust II
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.00%
Capital debt securities	$ 3,000
Junior subordinated debentures	$ 2,850	2,823
Trust Preferred Securities Subject to Mandatory Redemption \| M F B C Statutory Trust I
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.70%
Capital debt securities	$ 5,000
Junior subordinated debentures	$ 3,995	3,891
Trust Preferred Securities Subject to Mandatory Redemption \| Universal Preferred Trust
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.69%
Capital debt securities	$ 5,000
Junior subordinated debentures	$ 3,986	$ 3,883

Northwest Bancshares, Inc. 10-K