Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)(1)(i)

-URI http://asc.fasb.org/extlink&oid=7523297&loc=SL6224234-111729

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

-Number FAS140-4/FIN46(R)-8

-Paragraph B6

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 140

-Paragraph 17

-Subparagraph a(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6467456&loc=d3e113888-111728

+ Details

Name:	us-gaap_SecurityOwnedAndPledgedAsCollateralFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Companies Issuing Securities

+ References

No definition available.

+ Details

Name:	wash_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfCompaniesIssuingSecurities
Namespace Prefix:	wash_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

This represents the amortized cost for callable debt securities.

+ References

No definition available.

+ Details

Name:	wash_CallableDebtSecuritiesAmortizedCost
Namespace Prefix:	wash_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This represents the fair value for callable debt securities.

+ References

No definition available.

+ Details

Name:	wash_CallableDebtSecuritiesFairValue
Namespace Prefix:	wash_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Callable Debt Securities, Maturity Period

+ References

No definition available.

+ Details

Name:	wash_CallableDebtSecuritiesMaturityPeriod
Namespace Prefix:	wash_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

This represents the amortized cost for trust preferred securities for individual name issuers that are below investment grade.

+ References

No definition available.

+ Details

Name:	wash_TrustPreferredSecuritiesIndividualNameIssuerAmortizedCostBelowInvestmentGrade
Namespace Prefix:	wash_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This represents the unrealized losses for trust preferred securities for individual name issuers that are below investment grade.

+ References

No definition available.

+ Details

Name:	wash_TrustPreferredSecuritiesIndividualNameIssuerUnrealizedLossesBelowInvestmentGrade
Namespace Prefix:	wash_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Securities (Narrative) (Details) (USD $) In Millions, unless otherwise specified			6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Minimum [Member]	Jun. 30, 2013 Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities in unrealized loss position, number of companies issuing securities	7
Fair Value of Available for Sale and Held to Maturity securities pledged as collateral	$ 333.2	$ 386.5
Amortized cost of trust preferred securities of individual name issuers that are below investment grade	11.9
Unrealized losses of trust preferred securities of individual name issuers that are below investment grade	2.2
Amortized cost of callable debt securities	86.4
Fair value of callable debt securities	$ 82.1
Callable Debt Securities, Maturity Period			2 years	24 years