Borrowings (Long Term Debt) (Details) - USD ($)		Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Notes and subordinated debt		$ 575,499,000	$ 544,806,000
Debt issuance cost on senior fixed-rates		(2,930,000)	(3,030,000)
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)		17,486,000
Long-term debt		$ 571,212,000	$ 540,364,000
Variable interest rate		3.79%	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		$ (1,357,000)	$ (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	[1]	$ 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		$ 348,179,000	$ 317,486,000
Long-term Debt [Member]
Debt Instrument [Line Items]
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)		$ 48,179,000

[1] The interest rate on Webster Statutory Trust I floating-rate notes, which varies quarterly based on 3-month London Interbank Offered Rate plus 2.95%, was 3.79% at March 31, 2020 and 4.85% at December 31, 2019