Face (par) amount of debt instrument at time of issuance.

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

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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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Borrowings (Long Term Debt) (Details) - USD ($)	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Notes and subordinated debt	$ 572,822,000		$ 544,806,000
Debt issuance cost on senior fixed-rates	(2,729,000)		(3,030,000)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	345,502,000		317,486,000
Long-term debt	$ 568,846,000		$ 540,364,000
Variable interest rate	3.20%		4.85%
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	$ (1,247,000)		$ (1,412,000)
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	$ 345,502,000		317,486,000
Long-term Debt [Member]
Debt Instrument [Line Items]
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	$ 45,502,000	$ 48,200,000	$ 17,486,000