Derivative Financial Instruments (Narrative) (Details) $ in Thousands	Dec. 31, 2015 USD ($) derivative_instrument	Dec. 31, 2014 USD ($) derivative_instrument
Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 0	$ 22,681
Interest rate swaps with customers [Member]
Derivatives, Fair Value [Line Items]
Notional amount	302,142	165,795
Mirror swaps with counterparties [Member]
Derivatives, Fair Value [Line Items]
Notional amount	302,142	165,795
Risk participation-in agreement [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 21,474	$ 0
Designated as Hedging Instrument [Member] \| Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Number of derivative instruments held \| derivative_instrument		2
Notional amount		$ 22,681
Designated as Hedging Instrument [Member] \| Interest rate caps [Member]
Derivatives, Fair Value [Line Items]
Number of derivative instruments held \| derivative_instrument	2
Notional amount	$ 22,681
Interest rate cap premium	$ 257
Interest rate cap strike	4.50%
Not Designated as Hedging Instrument [Member] \| Interest rate swaps with customers [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 302,142	$ 165,795
Not Designated as Hedging Instrument [Member] \| Risk participation-out agreement [Member]
Derivatives, Fair Value [Line Items]
Notional amount	25,296
Not Designated as Hedging Instrument [Member] \| Risk participation-in agreement [Member]
Derivatives, Fair Value [Line Items]
Notional amount	$ 21,474

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

+ Details

Name:	invest_DerivativeNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Definition

Cap rate on an interest rate derivative such as an interest rate cap or collar. If market rates exceed the cap rate, a payment or receipt is triggered on the contract.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeCapInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5579245-113959

+ Details

Name:	us-gaap_DerivativeNumberOfInstrumentsHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The premium paid to enter into an interest rate cap agreement that will be amortized over the life of the contract.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=wash_InterestRateSwapwithcustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=wash_InterestRateMirrorSwapsWithCounterpartiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=wash_RiskparticipationinagreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_DesignatedAsHedgingInstrumentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateCapMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_HedgingDesignationAxis=us-gaap_NondesignatedMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=wash_RiskparticipationoutagreementMember
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