Loans (Troubled Debt Restructurings) (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
TDRs, Recorded Investment	$ 10,897		$ 10,897		$ 15,763
Specific Reserves on Troubled Debt Restructurings	233		233		159
TDRs, Commitment to Lend	$ 0		$ 0		0
Number of loans modified as a troubled debt restructuring	0	12	0	12
Pre-modifications TDR	$ 0	$ 5,615	$ 0	$ 5,615
Post-modifications TDR	$ 0	$ 5,615	$ 0	$ 5,615
Commercial Real Estate
Number of loans modified as a troubled debt restructuring	0	1	0	1
Pre-modifications TDR	$ 0	$ 841	$ 0	$ 841
Post-modifications TDR	$ 0	$ 841	$ 0	$ 841
Commercial & Industrial
Number of loans modified as a troubled debt restructuring	0	2	0	2
Pre-modifications TDR	$ 0	$ 460	$ 0	$ 460
Post-modifications TDR	$ 0	$ 460	$ 0	$ 460
Total Commercial
Number of loans modified as a troubled debt restructuring	0	3	0	3
Pre-modifications TDR	$ 0	$ 1,301	$ 0	$ 1,301
Post-modifications TDR	$ 0	$ 1,301	$ 0	$ 1,301
Residential Real Estate
Number of loans modified as a troubled debt restructuring	0	6	0	6
Pre-modifications TDR	$ 0	$ 3,512	$ 0	$ 3,512
Post-modifications TDR	$ 0	$ 3,512	$ 0	$ 3,512
Home Equity
Number of loans modified as a troubled debt restructuring	0	3	0	3
Pre-modifications TDR	$ 0	$ 802	$ 0	$ 802
Post-modifications TDR	$ 0	$ 802	$ 0	$ 802
Other
Number of loans modified as a troubled debt restructuring	0	0	0	0
Pre-modifications TDR	$ 0	$ 0	$ 0	$ 0
Post-modifications TDR	$ 0	$ 0	$ 0	$ 0
Total Consumer
Number of loans modified as a troubled debt restructuring	0	3	0	3
Pre-modifications TDR	$ 0	$ 802	$ 0	$ 802
Post-modifications TDR	0	$ 802	0	$ 802
Performing Financial Instruments
TDRs, Recorded Investment	8,619		8,619		13,418
Nonperforming Financial Instruments
TDRs, Recorded Investment	$ 2,278		$ 2,278		$ 2,345

Number of financing receivables that have been modified by troubled debt restructurings.

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount, before troubled debt restructuring, of financing receivable to be modified.

+ References

+ Details

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554

+ Details

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

- Definition

Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18794-111554

+ Details

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

- Definition

The amount of specific reserves on troubled debt restructurings.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wash_CommercialOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wash_HomeequityDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=wash_OtherconsumerDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: