Retirement Benefit Plans - Weighted Average Assumptions used to Determine Net Periodic Benefit Cost (Details)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2033	Dec. 31, 2030
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return on Plan Assets	5.50%
Forecast
Defined Benefit Plan Disclosure [Line Items]
Cost trend rate				4.75%	4.40%
Pension | Webster Bank Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.65%	2.29%	3.07%
Expected Long-Term Rate of Return on Plan Assets	5.50%	5.50%	5.75%
SERP | Webster Bank Supplemental Defined Benefit Plan for Executive Officers
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.45%	1.91%	2.82%
SERP | Astoria Bank Excess Benefit and Supplemental Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.58%
SERP | Astoria Bank Directors' Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.23%
SERP | Retirement Plan of the Greater New York Savings Bank for Non-Employee Directors
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.37%
SERP | Supplemental Executive Retirement Plan of Provident Bank
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.76%
SERP | Supplemental Executive Retirement Plan of Provident Bank - Other
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.38%
OPEB | Webster Bank Postretirement Medical Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	1.99%	1.40%	2.50%
Assumed Healthcare Cost Trend Rate	6.25%	6.50%	6.50%
OPEB | Sterling Bancorp Supplemental Postretirement Life Insurance Plan
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.35%
OPEB | Astoria Bank Postretirement Welfare Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.93%
Assumed Healthcare Cost Trend Rate	6.60%
OPEB | Split Dollar Life Insurance Arrangement
Defined Benefit Plan Disclosure [Line Items]
Discount Rate	2.20%