Borrowings (Long Term Debt) (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Notes and subordinated debt	$ 568,808,000	$ 571,484,000
Debt issuance cost on senior fixed-rates	(2,427,000)	(2,628,000)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	341,488,000	344,164,000
Long-term debt	$ 565,297,000	$ 567,663,000
Variable interest rate	3.07%	3.18%
London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	2.95%
Long-term Debt [Member]
Debt Instrument [Line Items]
Discount on senior fixed-rate notes	$ (1,084,000)	$ (1,193,000)
Junior subordinated debt Webster Statutory Trust I floating-rate notes due September 17, 2033 [Member]
Debt Instrument [Line Items]
Notes and subordinated debt	$ 77,320,000	77,320,000
Debt Instrument, Redemption, Period One [Member] \| 4.375% Senior fixed-rate notes due February 15, 2024 [Member]
Debt Instrument [Line Items]
Senior notes, interest rate (as a percent)	4.375%
Notes and subordinated debt	$ 150,000,000	150,000,000
Debt Instrument, Redemption, Period Two [Member] \| 4.375% Senior fixed-rate notes due February 15, 2024 [Member]
Debt Instrument [Line Items]
Senior notes, interest rate (as a percent)	4.10%
Notes and subordinated debt	$ 341,488,000	344,164,000
Long-term Debt [Member]
Debt Instrument [Line Items]
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	$ 41,488,000	$ 44,164,000

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Contractual interest rate for funds borrowed, under the debt agreement.

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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.

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Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

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Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

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