Derivative Financial Instruments (Fair Value of Derivatives by Balance Sheet Location) (Details) - USD ($) $ in Thousands		Dec. 31, 2022	Dec. 31, 2021
Derivatives, Fair Value [Line Items]
Accrued interest receivable		$ 17,600	$ 10,300
Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional amount		320,000	320,000
Interest rate swaps [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount	[1]	320,000	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]	548	182
Accrued interest receivable		24	182
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]	31,178	5,301
Accrued interest payable		856	19
Interest rate swaps with customers [Member]
Derivatives, Fair Value [Line Items]
Notional amount		935,099	1,022,388
Interest rate swaps with customers [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		935,099	1,022,388
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	32,361
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		68,137	2,015
Mirror swaps with counterparties [Member]
Derivatives, Fair Value [Line Items]
Notional amount		935,099	1,022,388
Mirror swaps with counterparties [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		935,099	1,022,388
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		67,797	2,001
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		61	32,480
Risk participation agreements [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		282,191	237,446
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		0	1
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]
Derivatives, Fair Value [Line Items]
Notional amount		12,201	49,800
Interest rate lock commitments [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		12,201	49,800
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		144	1,256
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		4	0
Forward sale commitments [Member]
Derivatives, Fair Value [Line Items]
Notional amount		23,150	103,626
Forward sale commitments [Member] | Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Notional amount		23,150	103,626
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		58	54
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		150	905
Derivative assets [Member]
Derivatives, Fair Value [Line Items]
Gross derivative assets		68,579	35,855
Less amounts offset in Consolidated Balance Sheets, derivative liabilities	[2]	23,524	2,167
Net amounts presented in Consolidated Balance Sheets, derivative assets		45,055	33,688
Less collateral pledged, derivatives assets	[3]	0	0
Net amounts		45,055	33,688
Derivative liabilities [Member]
Derivatives, Fair Value [Line Items]
Gross derivative liabilities		99,532	40,703
Less amounts offset in Consolidated Balance Sheets, derivative assets	[2]	23,524	2,167
Net amounts presented in Consolidated Balance Sheets, derivative liabilities		76,008	38,536
Less collateral pledged, derivative liabilities	[3]	7,716	34,539
Net amounts		$ 68,292	$ 3,997

[1] The fair value of derivative assets includes accrued interest receivable of $24 thousand and $182 thousand, respectively, at December 31, 2022 and 2021. The fair value of derivative liabilities includes accrued interest payable of $856 thousand and $19 thousand, respectively, at December 31, 2022 and 2021.

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

[3] 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.