Time Certificates of Deposit (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Time Certificates of Deposit [Abstract]
Time deposits greater than FDIC limit	$ 53.4	$ 45.1

Time deposits that meet or exceed the $250,000 FDIC limit

No definition available.

Name:	wash_TimedepositsgreaterthanFDIClimit
Namespace Prefix:	wash_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant