Derivative Financial Instruments (Fair Value of Derivatives by Balance Sheet Location) (Details) - USD ($) $ in Thousands		Dec. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Accrued interest receivable		$ 22,100	$ 22,900
Interest rate swaps [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount	[1]	120,000	120,000
Interest rate swaps [Member] | Designated as Hedging Instrument [Member] | Fair Value Hedging
Derivatives, Fair Value [Line Items]
Notional amount		100,000	0
Interest rate swaps [Member] | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value	[1]	1,529	802
Accrued interest receivable		120	239
Interest Rate Fair Value Hedge Asset at Fair Value		1,477	0
Interest rate swaps [Member] | Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value	[1]	229	1,119
Accrued interest payable		0
Interest Rate Fair Value Hedge Liability at Fair Value		0	0
Interest rate swaps with customers [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		886,912	938,872
Interest rate swaps with customers [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		2,468	6,594
Interest rate swaps with customers [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		51,372	52,102
Mirror swaps with counterparties [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		886,912	938,872
Mirror swaps with counterparties [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		51,176	51,859
Mirror swaps with counterparties [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		2,529	6,757
Risk participation agreements [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		343,935	321,055
Risk participation agreements [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		29	66
Risk participation agreements [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		0	1
Interest rate lock commitments [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		20,238	20,980
Interest rate lock commitments [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		248	504
Interest rate lock commitments [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		0	1
Forward sale commitments [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		52,100	50,117
Forward sale commitments [Member] | Not Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Derivative asset not designated as hedging instruments		163	18
Forward sale commitments [Member] | Not Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liability not designated as hedging instruments		291	711
Derivative assets [Member]
Derivatives, Fair Value [Line Items]
Gross derivative assets		57,090	59,843
Less amounts offset in Consolidated Balance Sheets, derivative liabilities	[2]	2,788	7,877
Net amounts presented in Consolidated Balance Sheets, derivative assets		54,302	51,966
Less collateral pledged, derivatives assets	[3]	0	0
Net amounts		54,302	51,966
Derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross derivative liabilities		54,451	60,691
Less amounts offset in Consolidated Balance Sheets, derivative assets	[2]	2,788	7,877
Net amounts presented in Consolidated Balance Sheets, derivative liabilities		51,663	52,814
Less collateral pledged, derivative liabilities	[3]	0	0
Net amounts		51,663	52,814
Interest Rate Collar | Designated as Hedging Instrument [Member] | Cash Flow Hedge [Member]
Derivatives, Fair Value [Line Items]
Notional amount		50,000	0
Interest Rate Collar | Designated as Hedging Instrument [Member] | Other assets [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge asset at fair value		0	0
Interest Rate Collar | Designated as Hedging Instrument [Member] | Other liabilities [Member]
Derivatives, Fair Value [Line Items]
Interest rate cash flow hedge liability at fair value		$ 30	$ 0

[1] The fair value of derivative assets includes accrued interest receivable of $120 thousand and $239 thousand, respectively, at December 31, 2024 and 2023. There was no accrued interest payable included in the fair value of derivative liabilities at December 31, 2024 and December 31, 2023.

[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.