Derivative Financial Instruments (Fair Value of Derivatives by Balance Sheet Location) (Details) - USD ($) $ in Thousands		Dec. 31, 2025	Dec. 31, 2024
Derivatives, Fair Value [Line Items]
Accrued interest receivable		$ 20,100	$ 22,100
Interest rate swaps | Derivatives Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount	[1]	120,000	120,000
Interest rate swaps | Derivatives Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value	[1]	126	1,529
Interest rate fair value hedge asset at fair value		335	1,477
Accrued interest receivable		35	120
Interest rate swaps | Derivatives Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value	[1]	979	229
Interest rate fair value hedge liability at fair value		0	0
Accrued interest payable		23	0
Interest rate swaps | Derivatives Designated as Hedging Instruments | Fair Value Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		100,000	100,000
Interest rate collars | Derivatives Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value		0	0
Interest rate collars | Derivatives Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value		17	30
Interest rate collars | Derivatives Designated as Hedging Instruments | Cash Flow Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		100,000	50,000
Interest rate floors | Derivatives Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value		125	0
Interest rate floors | Derivatives Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value		0	0
Interest rate floors | Derivatives Designated as Hedging Instruments | Cash Flow Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		200,000	0
Interest rate contracts with customers | Derivatives not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		882,941	886,912
Interest rate contracts with customers | Derivatives not Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		6,326	2,468
Interest rate contracts with customers | Derivatives not Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		27,959	51,372
Mirror interest rate contracts with counterparties | Derivatives not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		882,941	886,912
Mirror interest rate contracts with counterparties | Derivatives not Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		27,857	51,176
Mirror interest rate contracts with counterparties | Derivatives not Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		6,392	2,529
Risk participation agreements | Derivatives not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		304,854	343,935
Risk participation agreements | Derivatives not Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		28	29
Risk participation agreements | Derivatives not Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		1	0
Interest rate lock commitments | Derivatives not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		30,373	20,238
Interest rate lock commitments | Derivatives not Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		603	248
Interest rate lock commitments | Derivatives not Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		12	0
Forward sale commitments | Derivatives not Designated as Hedging Instruments
Derivatives, Fair Value [Line Items]
Notional amount		90,813	52,100
Forward sale commitments | Derivatives not Designated as Hedging Instruments | Other assets
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		13	163
Forward sale commitments | Derivatives not Designated as Hedging Instruments | Other liabilities
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		828	291
Derivative assets
Derivatives, Fair Value [Line Items]
Gross derivative assets		35,413	57,090
Less: derivative asset amounts offset	[2]	6,643	2,788
Derivative asset balances, net of offset		28,770	54,302
Less collateral pledged, derivative assets	[3]	0	0
Net amounts		28,770	54,302
Derivative liabilities
Derivatives, Fair Value [Line Items]
Gross derivative liabilities		36,188	54,451
Less: derivative liability amounts offset	[2]	6,643	2,788
Derivative liability balances, net of offset		29,545	51,663
Less collateral pledged, derivative liabilities	[3]	0	0
Net amounts		$ 29,545	$ 51,663

[1] The fair value of derivative assets includes accrued interest receivable of $35 thousand and $120 thousand, respectively, at December 31, 2025 and 2024. The fair value of derivative liabilities includes accrued interest payable of $23 thousand at December 31, 2025. There was no accrued interest payable included in the fair value of derivative liabilities at December 31, 2024.

[2] Interest rate risk management contracts and loan related derivative contracts with counterparties are subject to master netting arrangements.

[3] Collateral contractually required to be pledged to derivative counterparties is in the form of cash. Washington Trust may need to post additional collateral in the future in proportion to potential increases in unrealized loss positions.