Derivative Financial Instruments (Fair Value of Derivatives by Balance Sheet Location) (Details) - USD ($) $ in Thousands		Dec. 31, 2021	Dec. 31, 2020
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		$ 182	$ 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		5,301	1,958
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		32,361	75,804
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		2,015	68
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		2,001	67
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		32,480	76,248
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		1	22
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		2	2
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		1,256	7,202
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	0
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		54	0
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		905	2,914
Derivative assets [Member]
Derivatives, Fair Value [Line Items]
Gross derivative assets		35,855	83,095
Less amounts offset in Consolidated Balance Sheets, derivative liabilities	[1]	2,167	67
Net amounts presented in Consolidated Balance Sheets, derivative assets		33,688	83,028
Less collateral pledged, derivatives assets	[2]	0	0
Net amounts		33,688	83,028
Derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross derivative liabilities		40,703	81,190
Less amounts offset in Consolidated Balance Sheets, derivative assets	[1]	2,167	67
Net amounts presented in Consolidated Balance Sheets, derivative liabilities		38,536	81,123
Less collateral pledged, derivative liabilities	[2]	34,539	74,698
Net amounts		$ 3,997	$ 6,425

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

[2] Collateral 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.