Subsequent Events (Details) shares in Thousands	Mar. 31, 2022 shares
Subsequent Events [Abstract]
Maximum shares under 2022 Incentive Plan	600

The maximum number of shares that can be issued under the 2022 Washington Trust Bancorp, Inc. Long Term Incentive Plan

No definition available.

Name:	wash_MaximumSharesUnder2022IncentivePlan
Namespace Prefix:	wash_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant