Summary of Significant Accounting Policies	6 Months Ended
Jun. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Significant Accounting Policies [Text Block]	Summary of Significant Accounting Policies Nature of Operations Webster Financial Corporation (the Holding Company) is a bank holding company and financial holding company under the Bank Holding Company Act, incorporated under the laws of Delaware in 1986 and headquartered in Waterbury, Connecticut. The Holding Company's principal asset is all of the outstanding capital stock of Webster Bank, National Association (Webster Bank). Webster delivers financial services to individuals, families, and businesses primarily within its regional footprint from New York to Massachusetts. Webster provides business and consumer banking, mortgage lending, financial planning, trust, and investment services through banking offices, ATMs, mobile banking, and its internet website (www.websterbank.com or www.wbst.com). Webster also offers equipment financing, commercial real estate lending, and asset-based lending primarily across the Northeast. On a nationwide basis, through its HSA Bank division, Webster Bank offers and administers health savings accounts, flexible spending accounts, health reimbursement accounts, and commuter benefits. Basis of Presentation The accounting and reporting policies of the Company that materially affect its financial statements conform with GAAP. The accompanying unaudited Condensed Consolidated Financial Statements of the Company have been prepared in conformity with the instructions for Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all the information and notes required by GAAP for complete financial statements and should be read in conjunction with the Company's Consolidated Financial Statements, and related Notes, for the year ended December 31, 2018, included in our Form 10-K filed with the SEC. Certain prior period amounts have been reclassified to conform to the current year's presentation. These reclassifications had an immaterial effect on the Company's consolidated financial statements. Use of Estimates The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities as well as income and expense during the reporting period. Actual results could differ from those estimates. Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for the full year or any future period. Accounting Standards Adopted During 2019 Effective January 1, 2019, the following ASUs were adopted by the Company: ASU No. 2018-16, Derivatives and Hedging (Topic 815) - Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes. The Update permits the use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under Topic 815 in addition to the interest rates on direct U.S. Treasury obligations, the London Interbank Offered Rate swap rate, the OIS rate based on the Fed Funds Effective Rate, and the Securities Industry and Financial Markets Association Municipal Swap Rate. The Company adopted the Update during the first quarter of 2019 on a prospective basis. The adoption of this guidance did not have a material effect on the Company's consolidated financial statements. ASU No. 2017-12, Derivatives and Hedging (Topic 815) - Targeted Improvements to Accounting for Hedging Activities. The purpose of the Update is to better align a company’s risk management and financial reporting for hedging activities with the economic objectives of those activities. The Update expands an entity's ability to hedge non-financial and financial risk components and reduce complexity in hedges of interest rate risk. The guidance eliminates the requirement to separately measure and report hedge ineffectiveness, and generally requires the entire change in fair value of a hedging instrument to be presented in the same income statement line in which the earnings effect of the hedged item is reported. The Company adopted the Update during the first quarter of 2019 on a modified retrospective basis. The adoption of this guidance did not have a material effect on the Company's consolidated financial statements. The Company has provided enhanced disclosures in Note 13: Derivative Financial Instruments as a result of adopting this Update. ASU No. 2016-02, Leases (Topic 842) and subsequent ASUs issued to amend this Topic. The Updates introduce a lessee model that requires substantially all leases to be recorded as assets and liabilities on the balance sheet and requires expanded quantitative and qualitative disclosures regarding key information about leasing arrangements. The lessor model remains substantially the same with targeted improvements that do not materially impact the Company. The Company adopted the Updates during the first quarter of 2019 using the new transition method option that allows the use of effective date, January 1, 2019, as the date of initial application of the new lease accounting standard and to recognize a cumulative-effect adjustment to the opening balance of retained earnings upon adoption. The Company elected the transition relief package of practical expedients which forgoes the requirement to reassess the existence of leases in existing contracts, their lease classification and the accounting treatment of their initial direct costs. As a practical expedient, the Company has also made a policy election to not separate non-lease components from lease components for its real estate leases and instead account for each separate lease components and non-lease components associated with that lease component as a single lease component. The Company will separately account for the lease and non-lease components in its equipment leases. The Company determines whether a contract contains a lease based on whether a contract, or a part of a contract, conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The discount rate used is either the rate implicit in the lease, or when a rate cannot be readily determined an incremental borrowing rate. The incremental borrowing rate is the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term and amount equal to the lease payments, in a similar economic environment. As a result of adopting this Update, the Company recognized $157.2 million of right-of-use asset (ROU) and $178.2 million of lease liability, as of January 1, 2019. The Company also recorded a $0.5 million cumulative-effect adjustment directly to retained earnings as of January 1, 2019 for abandoned leased properties and the remaining deferred gains on sale-leaseback transactions which occurred prior to the date of adoption. See Note 9: Leasing for further information. Accounting Standards Issued But Not Yet Adopted The following list identifies ASUs applicable to the Company that have been issued by the Financial Accounting Standards Board (FASB) but are not yet effective: ASU No. 2019-04, Codification Improvements to Topic 326, Financial Instruments - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments. The Update amends guidance on credit losses, hedge accounting, and recognition and measurement of financial instruments. The changes provide clarifications and codification improvements in relation to recently issued accounting updates. The amendments to the guidance on credit losses are considered in the paragraphs below related to our adoption of ASU 2016-13, and will be adopted concurrently with those Updates. The clarifications and amendments to the guidance on hedge accounting and recognition and measurement of financial instruments will be effective for the Company on January 1, 2020. The Company does not expect these changes to have a material impact on its consolidated financial statements. ASU No. 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40) - Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. The Update aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The updated guidance also requires an entity to amortize the capitalized implementation costs as an expense over the term of the hosting arrangement and to present in the same income statement line item as the fees associated with the hosting arrangement. The Update is effective for the Company on January 1, 2020. Early adoption is permitted, although the Company does not intend to early adopt. The Company will apply the amendments in this update prospectively to all implementation costs incurred after the date of adoption. The Company does not expect this Update to have a material impact on its consolidated financial statements. ASU No. 2018-14, Compensation-Retirement Benefits - Defined Benefit Plan - General (Subtopic 715-20) - Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans. The Update modifies the disclosure requirements for employers that sponsor defined benefit pension plans and other postretirement plans. The updated guidance will be effective for the Company on January 1, 2021. The Company does not expect this Update to have a material impact on its consolidated financial statements. ASU No. 2018-13, Fair Value Measurement (Topic 820) - Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement. The Update modifies the disclosure requirements on fair value measurements. The updated guidance will no longer require entities to disclose the amount and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy. However, it will require public companies to disclose changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average of significant unobservable inputs used to develop Level 3 measurements. The Update is effective for the Company on January 1, 2020, and earlier adoption is permitted. The Company does not expect this Update to have a material impact on its consolidated financial statements. ASU No. 2017-04, Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment. The Update simplifies quantitative goodwill impairment testing by requiring entities to compare the fair value of a reporting unit with its carrying amount and recognize an impairment charge for any amount by which the carrying amount exceeds the reporting unit's fair value, to the extent that the loss recognized does not exceed the amount of goodwill allocated to that reporting unit. This changes current guidance by eliminating the second step of the goodwill impairment analysis which involves calculating the implied fair value of goodwill determined in the same manner as the amount of goodwill recognized in a business combination upon acquisition. Entities will still have the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The Update must be applied prospectively and is effective for the Company on January 1, 2020. Early adoption is permitted. The Company does not expect this new guidance to have a material impact on its consolidated financial statements. ASU No. 2016-13, Financial Instruments - Credit Losses (Topic 326) - Measurement of Credit Losses on Financial Instruments and subsequent ASUs issued to clarify this Topic. Current GAAP requires an incurred loss methodology for recognizing credit losses. This approach requires recognition of credit losses when it is probable a loss has been incurred. The main objective of this Update is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. To achieve this objective, the amendments in this Update will replace today's incurred loss approach with a new credit loss methodology known as the Current Expected Credit Loss (CECL) model which requires earlier recognition of credit losses using a lifetime credit loss measurement approach for financial assets carried at amortized cost. The CECL model requires consideration of a broader range of reasonable and supportable information to determine credit loss estimates. The change from an incurred loss method to an expected loss method represents a fundamental shift from existing GAAP and may result in a material increase to the Company's accounting for credit losses on financial instruments. To prepare for implementation of the new standard the Company has established a project lead and has empowered a steering committee comprised of members from different disciplines including Credit, Accounting, Finance, IT, and Treasury, as well as specific working groups to focus on key components of the development process. Through these working groups, the Company has begun to evaluate the effect that this Update, including the subsequent ASUs issued to clarify this Topic, will have on its financial statements and related disclosures. An implementation project plan has been created and is made up of targeted work streams focused on credit models, data management, treasury, and accounting. These work streams are collectively assessing required resources, use of existing and new models, and data availability. The new credit models will include additional assumptions used to calculate credit losses over the estimated life of the financial assets and will include the impact of forecasted macroeconomic conditions. The Company has contracted with system solution providers and is in the process of implementing the selected solutions. During 2019, the Company is focused on model validations as well as the development of processes and related controls. The Company will conduct a parallel run in the second half of 2019. These Updates are effective for the Company on January 1, 2020. The adoption of these Updates is expected to increase the Company's allowance for loan and lease losses. The magnitude of the increase will depend on the composition, characteristics, and credit quality of our loan and securities portfolios as well as the economic conditions in effect at the adoption date.

Webster Financial Corporation (the Holding Company) is a bank holding company and financial holding company under the Bank Holding Company Act, incorporated under the laws of Delaware in 1986 and headquartered in Waterbury, Connecticut. The Holding Company's principal asset is all of the outstanding capital stock of Webster Bank, National Association (Webster Bank).

Webster delivers financial services to individuals, families, and businesses primarily within its regional footprint from New York to Massachusetts. Webster provides business and consumer banking, mortgage lending, financial planning, trust, and investment services through banking offices, ATMs, mobile banking, and its internet website (www.websterbank.com or www.wbst.com). Webster also offers equipment financing, commercial real estate lending, and asset-based lending primarily across the Northeast. On a nationwide basis, through its HSA Bank division, Webster Bank offers and administers health savings accounts, flexible spending accounts, health reimbursement accounts, and commuter benefits.

The accounting and reporting policies of the Company that materially affect its financial statements conform with GAAP. The accompanying unaudited Condensed Consolidated Financial Statements of the Company have been prepared in conformity with the instructions for Form 10-Q and Rule 10-01 of Regulation S-X. Accordingly, they do not include all the information and notes required by GAAP for complete financial statements and should be read in conjunction with the Company's Consolidated Financial Statements, and related Notes, for the year ended December 31, 2018, included in our Form 10-K filed with the SEC.

The preparation of financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities as well as income and expense during the reporting period. Actual results could differ from those estimates. Operating results for the interim periods disclosed herein are not necessarily indicative of the results that may be expected for the full year or any future period.

The Update permits the use of the OIS rate based on SOFR as a U.S. benchmark interest rate for hedge accounting purposes under Topic 815 in addition to the interest rates on direct U.S. Treasury obligations, the London Interbank Offered Rate swap rate, the OIS rate based on the Fed Funds Effective Rate, and the Securities Industry and Financial Markets Association Municipal Swap Rate.

The purpose of the Update is to better align a company’s risk management and financial reporting for hedging activities with the economic objectives of those activities. The Update expands an entity's ability to hedge non-financial and financial risk components and reduce complexity in hedges of interest rate risk. The guidance eliminates the requirement to separately measure and report hedge ineffectiveness, and generally requires the entire change in fair value of a hedging instrument to be presented in the same income statement line in which the earnings effect of the hedged item is reported.

The Company adopted the Update during the first quarter of 2019 on a modified retrospective basis. The adoption of this guidance did not have a material effect on the Company's consolidated financial statements. The Company has provided enhanced disclosures in Note 13: Derivative Financial Instruments as a result of adopting this Update.

The Updates introduce a lessee model that requires substantially all leases to be recorded as assets and liabilities on the balance sheet and requires expanded quantitative and qualitative disclosures regarding key information about leasing arrangements. The lessor model remains substantially the same with targeted improvements that do not materially impact the Company.

The Company adopted the Updates during the first quarter of 2019 using the new transition method option that allows the use of effective date, January 1, 2019, as the date of initial application of the new lease accounting standard and to recognize a cumulative-effect adjustment to the opening balance of retained earnings upon adoption. The Company elected the transition relief package of practical expedients which forgoes the requirement to reassess the existence of leases in existing contracts, their lease classification and the accounting treatment of their initial direct costs. As a practical expedient, the Company has also made a policy election to not separate non-lease components from lease components for its real estate leases and instead account for each separate lease components and non-lease components associated with that lease component as a single lease component. The Company will separately account for the lease and non-lease components in its equipment leases. The Company determines whether a contract contains a lease based on whether a contract, or a part of a contract, conveys the right to control the use of an identified asset for a period of time in exchange for consideration. The discount rate used is either the rate implicit in the lease, or when a rate cannot be readily determined an incremental borrowing rate. The incremental borrowing rate is the rate of interest that the Company would have to pay to borrow on a collateralized basis over a similar term and amount equal to the lease payments, in a similar economic environment.

As a result of adopting this Update, the Company recognized $157.2 million of right-of-use asset (ROU) and $178.2 million of lease liability, as of January 1, 2019. The Company also recorded a $0.5 million cumulative-effect adjustment directly to retained earnings as of January 1, 2019 for abandoned leased properties and the remaining deferred gains on sale-leaseback transactions which occurred prior to the date of adoption. See Note 9: Leasing for further information.

The Update amends guidance on credit losses, hedge accounting, and recognition and measurement of financial instruments. The changes provide clarifications and codification improvements in relation to recently issued accounting updates. The amendments to the guidance on credit losses are considered in the paragraphs below related to our adoption of ASU 2016-13, and will be adopted concurrently with those Updates. The clarifications and amendments to the guidance on hedge accounting and recognition and measurement of financial instruments will be effective for the Company on January 1, 2020. The Company does not expect these changes to have a material impact on its consolidated financial statements.

The Update aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The updated guidance also requires an entity to amortize the capitalized implementation costs as an expense over the term of the hosting arrangement and to present in the same income statement line item as the fees associated with the hosting arrangement.

The Update is effective for the Company on January 1, 2020. Early adoption is permitted, although the Company does not intend to early adopt. The Company will apply the amendments in this update prospectively to all implementation costs incurred after the date of adoption. The Company does not expect this Update to have a material impact on its consolidated financial statements.

The Update modifies the disclosure requirements on fair value measurements. The updated guidance will no longer require entities to disclose the amount and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy. However, it will require public companies to disclose changes in unrealized gains and losses for the period included in other comprehensive income for recurring Level 3 fair value measurements held at the end of the reporting period and the range and weighted average of significant unobservable inputs used to develop Level 3 measurements.

The Update simplifies quantitative goodwill impairment testing by requiring entities to compare the fair value of a reporting unit with its carrying amount and recognize an impairment charge for any amount by which the carrying amount exceeds the reporting unit's fair value, to the extent that the loss recognized does not exceed the amount of goodwill allocated to that reporting unit.

This changes current guidance by eliminating the second step of the goodwill impairment analysis which involves calculating the implied fair value of goodwill determined in the same manner as the amount of goodwill recognized in a business combination upon acquisition. Entities will still have the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary.

Current GAAP requires an incurred loss methodology for recognizing credit losses. This approach requires recognition of credit losses when it is probable a loss has been incurred. The main objective of this Update is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. To achieve this objective, the amendments in this Update will replace today's incurred loss approach with a new credit loss methodology known as the Current Expected Credit Loss (CECL) model which requires earlier recognition of credit losses using a lifetime credit loss measurement approach for financial assets carried at amortized cost. The CECL model requires consideration of a broader range of reasonable and supportable information to determine credit loss estimates.

The change from an incurred loss method to an expected loss method represents a fundamental shift from existing GAAP and may result in a material increase to the Company's accounting for credit losses on financial instruments. To prepare for implementation of the new standard the Company has established a project lead and has empowered a steering committee comprised of members from different disciplines including Credit, Accounting, Finance, IT, and Treasury, as well as specific working groups to focus on key components of the development process. Through these working groups, the Company has begun to evaluate the effect that this Update, including the subsequent ASUs issued to clarify this Topic, will have on its financial statements and related disclosures. An implementation project plan has been created and is made up of targeted work streams focused on credit models, data management, treasury, and accounting. These work streams are collectively assessing required resources, use of existing and new models, and data availability. The new credit models will include additional assumptions used to calculate credit losses over the estimated life of the financial assets and will include the impact of forecasted macroeconomic conditions. The Company has contracted with system solution providers and is in the process of implementing the selected solutions. During 2019, the Company is focused on model validations as well as the development of processes and related controls. The Company will conduct a parallel run in the second half of 2019.