Loans Loans (Narrative - Credit Quality Indicators) (Details)	Dec. 31, 2014 rating	Dec. 31, 2013 rating
Receivables [Abstract]
Weighted Average Risk Rating, Commercial Loans	4.67	4.64

The represents the weighted average risk rating for commercial loans.

No definition available.

Name:	wash_WeightedAverageRiskRatingCommercialLoans
Namespace Prefix:	wash_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant