Loans and Leases (Nonaccrual) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	$ 282,841	$ 208,525
Non-accrual with No Allowance	28,129	39,037
Commercial Portfolio Segment [Member]
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	251,118	179,134
Non-accrual with No Allowance	14,855	25,661
Commercial Portfolio Segment [Member] \| Commercial non-mortgage
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	193,294	122,855
Non-accrual with No Allowance	12,367	20,066
Commercial Portfolio Segment [Member] \| Asset-based
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	34,893	35,068
Non-accrual with No Allowance	1,155	1,330
Commercial Portfolio Segment [Member] \| Commercial real estate
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	3,815	11,383
Non-accrual with No Allowance	0	2,681
Commercial Portfolio Segment [Member] \| Multi-family
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	10,439	0
Non-accrual with No Allowance	957	0
Commercial Portfolio Segment [Member] \| Equipment financing
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	8,677	9,828
Non-accrual with No Allowance	376	1,584
Consumer Portfolio Segment [Member]
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	31,723	29,391
Non-accrual with No Allowance	13,274	13,376
Consumer Portfolio Segment [Member] \| Residential
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	8,589	5,704
Non-accrual with No Allowance	1,690	856
Consumer Portfolio Segment [Member] \| Home equity
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	22,934	23,545
Non-accrual with No Allowance	11,546	12,471
Consumer Portfolio Segment [Member] \| Other consumer
Financing Receivable, Nonaccrual [Line Items]
Non-accrual	200	142
Non-accrual with No Allowance	$ 38	$ 49

Amortized cost of financing receivable on nonaccrual status with no allowance for credit loss. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

+ Details

Name:	us-gaap_FinancingReceivableNonaccrualNoAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

+ Details

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

- Definition

Amortized cost of financing receivable on nonaccrual status. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)
-Publisher SEC

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (2)
-Publisher SEC

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481962/310-10-50-7

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=naics_ZZ522291
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: