Cover Page - shares	6 Months Ended
	Jun. 30, 2021	Jul. 31, 2021
Cover [Abstract]
Entity Address, Address Line One	23 Broad Street
Entity Address, City or Town	Westerly,
Entity Address, State or Province	RI
Entity Incorporation, State or Country Code	RI
Document Transition Report	false
Document Quarterly Report	true
Entity Registrant Name	Washington Trust Bancorp Inc
Entity Central Index Key	0000737468
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-Q
Entity File Number	001-32991
City Area Code	401
Local Phone Number	348-1200
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Title of 12(g) Security	COMMON STOCK, $.0625 PAR VALUE PER SHARE
Trading Symbol	WASH
Security Exchange Name	NASDAQ
Entity Common Stock, Shares Outstanding		17,320,449
Entity Tax Identification Number	05-0404671
Entity Address, Postal Zip Code	02891