Loans (Narrative - Troubled Debt Restructurings) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014
Receivables [Abstract]
Troubled debt restructured loans, management determination of loans on nonaccrual status to return to accrual status, period	6 months
Time loan is reported as TDR from date of restructuring	1 year
Recorded investment	$ 18.5	$ 18.4
Specific reserves on troubled debt restructurings	$ 1.8	$ 1.2

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

+ Details

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Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

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- Definition

The number of months for which loans which are already on nonaccrual status at the time of the restructuring, continue to remain on nonaccrual status before management will consider such loans for returning to accruing status.

+ References

No definition available.

+ Details

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Namespace Prefix:	wash_
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Period Type:	duration

- Definition

The amount of specific reserves on troubled debt restructurings.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This represents the amount of time that a troubled debt restructured loan is reported as such from the date of restructuring

+ References

No definition available.

+ Details

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Period Type:	duration