Retirement Benefit Plans - Weighted Average Assumptions used to Determine Benefit Obligations (Details)	Dec. 31, 2022	Dec. 31, 2021
Pension | Webster Bank Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.96%	2.65%
SERP | Webster Bank Supplemental Defined Benefit Plan for Executive Officers
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.88%	2.45%
SERP | Astoria Bank Excess Benefit and Supplemental Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.77%
SERP | Astoria Bank Directors' Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.70%
SERP | Retirement Plan of the Greater New York Savings Bank for Non-Employee Directors
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.70%
SERP | Supplemental Executive Retirement Plan of Provident Bank
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	5.04%
SERP | Supplemental Executive Retirement Plan of Provident Bank - Other
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.90%
OPEB | Webster Bank Postretirement Medical Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.72%	1.99%
OPEB | Sterling Bancorp Supplemental Postretirement Life Insurance Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.70%
OPEB | Astoria Bank Postretirement Welfare Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.94%
OPEB | Split Dollar Life Insurance Arrangement
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	4.63%