Summary of Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements of Webster have been prepared in accordance with GAAP for interim financial information and Article 10 of Regulation S-X. Certain information and footnote disclosures required by GAAP for complete financial statements have been omitted or condensed. Therefore, the condensed consolidated financial statements should be read in conjunction with Webster's Annual Report on Form 10-K for the year ended December 31, 2021. The results of operations for the three months ended March 31, 2022 are not necessarily indicative of the future results that may be attained for the entire year or other interim periods. In the opinion of management, all necessary adjustments have been reflected to present fairly the financial position, results of operations, and cash flows for the reporting periods presented. Intercompany transactions and balances have been eliminated in consolidation. Assets under administration or assets under management that Webster holds or manages in a fiduciary or agency capacity for customers are not included in the consolidated financial statements.
Reclassifications	ReclassificationsCertain prior period amounts have been reclassified to conform to the current period presentation. These reclassifications did not have a significant impact on the Company's consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Business Combinations	Business Combinations Business combinations are accounted for under the acquisition method, in which the identifiable assets acquired and liabilities assumed are generally measured and recognized at fair value as of the acquisition date, with the excess of the purchase price over the fair value of the net assets acquired capitalized as goodwill. Items such as acquired right-of-use (ROU) lease assets and operating lease liabilities as lessee, employee benefit plans, and income-tax related balances are recognized in accordance with other applicable GAAP, which may result in measurements that differ from fair value. Business combinations are included in the consolidated financial statements from the respective dates of acquisition. Historical reporting periods reflect only the results of legacy Webster operations. Merger-related costs are expensed in their applicable non-interest expense categories in the period incurred. Additional information regarding Webster's mergers and acquisitions can be found within Note 2: Mergers and Acquisitions.
Purchased Credit-Deteriorated Loans and Leases	Purchased Credit-Deteriorated Loans and Leases Purchased credit-deteriorated (PCD) loans and leases are defined as those that have experienced a more-than-insignificant deterioration in credit quality since origination. Webster considers a variety of factors to evaluate and identify whether acquired loans are PCD, including but not limited to, nonaccrual status, delinquency, TDR classification, partial charge-offs, decreases in FICO scores, risk rating downgrades, and other factors. Upon acquisition, expected credit losses are added to the fair value of individual PCD loans and leases to determine the amortized cost basis. After initial recognition, any changes to the estimate of expected credit losses, favorable or unfavorable, are recorded as a provision for credit loss during the period of change. PCD accounting is also applied to loans and leases previously charged-off by the acquiree if Webster has contractual rights to the cash flows at the acquisition date. Webster recognizes an additional allowance for credit loss for these amounts previously charged-off by the acquiree with a corresponding increase to the amortized costs basis. Balances deemed to be uncollectible are immediately charged-off in accordance with Webster’s charge-off policies, resulting in the establishment of the initial allowance for credit losses for PCD loans and leases to be recorded net of these uncollectible balances.
Relevant Accounting Standards Issued But Not Yet Adopted	Relevant Accounting Standards Issued But Not Yet Adopted In March 2022, the FASB issued ASU No. 2022-02—Financial Instruments—Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures, which eliminates the accounting guidance for TDRs by creditors in Subtopic 310-40, Receivables—Troubled Debt Restructurings by Creditors, while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty. Specifically, rather than applying the recognition and measurement guidance for TDRs, an entity must apply the loan refinancing and restructuring guidance in paragraphs 310-20-35-9 through 35-11 to determine whether a modification results in a new loan or a continuation of an existing loan. In addition, ASU No. 2022-02 requires that an entity disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases within the scope of Subtopic 326-20, Financial Instruments—Credit Losses—Measured at Amortized Cost in the vintage disclosures required by paragraph 326-20-50-6. ASU No. 2022-02 is effective for fiscal years beginning after December 15, 2022, with early adoption permitted. The amendments should be applied prospectively, however, an entity has the option to apply a modified retrospective transition method related to the recognition and measurement of TDRs, which would result in a cumulative effect adjustment to retained earnings in the period of adoption. The Company is in the early assessment stage of evaluating the amendments, as well as determining under which transition method it plans to adopt for TDRs. Therefore, the Company is currently unable to reasonably estimate the impact of adoption on the consolidated financial statements.

Summary of Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2022

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The unaudited condensed consolidated financial statements of Webster have been prepared in accordance with GAAP for interim financial information and Article 10 of Regulation S-X. Certain information and footnote disclosures required by GAAP for complete financial statements have been omitted or condensed. Therefore, the condensed consolidated financial statements should be read in conjunction with Webster's Annual Report on Form 10-K for the year ended December 31, 2021. The results of operations for the three months ended March 31, 2022 are not necessarily indicative of the future results that may be attained for the entire year or other interim periods.

In the opinion of management, all necessary adjustments have been reflected to present fairly the financial position, results of operations, and cash flows for the reporting periods presented. Intercompany transactions and balances have been eliminated in consolidation. Assets under administration or assets under management that Webster holds or manages in a fiduciary or agency capacity for customers are not included in the consolidated financial statements.

Reclassifications

ReclassificationsCertain prior period amounts have been reclassified to conform to the current period presentation. These reclassifications did not have a significant impact on the Company's consolidated financial statements.

Use of Estimates

The preparation of the consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Business Combinations

Business combinations are accounted for under the acquisition method, in which the identifiable assets acquired and liabilities assumed are generally measured and recognized at fair value as of the acquisition date, with the excess of the purchase price over the fair value of the net assets acquired capitalized as goodwill. Items such as acquired right-of-use (ROU) lease assets and operating lease liabilities as lessee, employee benefit plans, and income-tax related balances are recognized in accordance with other applicable GAAP, which may result in measurements that differ from fair value. Business combinations are included in the consolidated financial statements from the respective dates of acquisition. Historical reporting periods reflect only the results of legacy Webster operations. Merger-related costs are expensed in their applicable non-interest expense categories in the period incurred. Additional information regarding Webster's mergers and acquisitions can be found within Note 2: Mergers and Acquisitions.

Purchased Credit-Deteriorated Loans and Leases

Purchased credit-deteriorated (PCD) loans and leases are defined as those that have experienced a more-than-insignificant deterioration in credit quality since origination. Webster considers a variety of factors to evaluate and identify whether acquired loans are PCD, including but not limited to, nonaccrual status, delinquency, TDR classification, partial charge-offs, decreases in FICO scores, risk rating downgrades, and other factors. Upon acquisition, expected credit losses are added to the fair value of individual PCD loans and leases to determine the amortized cost basis. After initial recognition, any changes to the estimate of expected credit losses, favorable or unfavorable, are recorded as a provision for credit loss during the period of change.

PCD accounting is also applied to loans and leases previously charged-off by the acquiree if Webster has contractual rights to the cash flows at the acquisition date. Webster recognizes an additional allowance for credit loss for these amounts previously charged-off by the acquiree with a corresponding increase to the amortized costs basis. Balances deemed to be uncollectible are immediately charged-off in accordance with Webster’s charge-off policies, resulting in the establishment of the initial allowance for credit losses for PCD loans and leases to be recorded net of these uncollectible balances.

Relevant Accounting Standards Issued But Not Yet Adopted

In March 2022, the FASB issued ASU No. 2022-02—Financial Instruments—Credit Losses (Topic 326): Troubled Debt Restructurings and Vintage Disclosures, which eliminates the accounting guidance for TDRs by creditors in Subtopic 310-40, Receivables—Troubled Debt Restructurings by Creditors, while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty. Specifically, rather than applying the recognition and measurement guidance for TDRs, an entity must apply the loan refinancing and restructuring guidance in paragraphs 310-20-35-9 through 35-11 to determine whether a modification results in a new loan or a continuation of an existing loan. In addition, ASU No. 2022-02 requires that an entity disclose current-period gross write-offs by year of origination for financing receivables and net investments in leases within the scope of Subtopic 326-20, Financial Instruments—Credit Losses—Measured at Amortized Cost in the vintage disclosures required by paragraph 326-20-50-6.

ASU No. 2022-02 is effective for fiscal years beginning after December 15, 2022, with early adoption permitted. The amendments should be applied prospectively, however, an entity has the option to apply a modified retrospective transition method related to the recognition and measurement of TDRs, which would result in a cumulative effect adjustment to retained earnings in the period of adoption. The Company is in the early assessment stage of evaluating the amendments, as well as determining under which transition method it plans to adopt for TDRs. Therefore, the Company is currently unable to reasonably estimate the impact of adoption on the consolidated financial statements.