Derivative Financial Instruments (Fair Value of Derivatives by Balance Sheet Location) (Details) - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Accrued interest receivable		$ 22,900	$ 17,600
Interest rate swaps [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount	[1]	120,000	320,000
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]	802	548
Accrued interest receivable		239	24
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]	1,119	31,178
Accrued interest payable		0	856
Interest rate swaps with customers [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		938,872	935,099
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		6,594	32
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		52,102	68,137
Mirror swaps with counterparties [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		938,872	935,099
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		51,859	67,797
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		6,757	61
Risk participation agreements [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		321,055	282,191
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		66	0
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		1	2
Interest rate lock commitments [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		20,980	12,201
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		504	144
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		1	4
Forward sale commitments [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		50,117	23,150
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		18	58
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		711	150
Derivative assets [Member]
Derivatives, Fair Value [Line Items]
Gross derivative assets		59,843	68,579
Less amounts offset in Consolidated Balance Sheets, derivative liabilities	[2]	7,877	23,524
Net amounts presented in Consolidated Balance Sheets, derivative assets		51,966	45,055
Less collateral pledged, derivatives assets	[3]	0	0
Net amounts		51,966	45,055
Derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross derivative liabilities		60,691	99,532
Less amounts offset in Consolidated Balance Sheets, derivative assets	[2]	7,877	23,524
Net amounts presented in Consolidated Balance Sheets, derivative liabilities		52,814	76,008
Less collateral pledged, derivative liabilities	[3]	0	7,716
Net amounts		$ 52,814	$ 68,292

[1] The fair value of derivative assets includes accrued interest receivable of $239 thousand and $24 thousand, respectively, at December 31, 2023 and 2022. There was no accrued interest payable included in the fair value of derivative liabilities at December 31, 2023, compared to $856 thousand of accrued interest payable at December 31, 2022.

[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.