Benefit Plans - Schedule of Discount Rates Used to Determine Benefit Obligations (Details)	Dec. 31, 2016	Dec. 31, 2015
Astoria Bank | Pension Plan
Benefit Plans
Discount rate	3.92%	4.09%
Astoria Bank | Astoria Excess and Supplemental Benefit Plans
Benefit Plans
Discount rate	3.70%	3.86%
Astoria Bank | Directors' Retirement Plan
Benefit Plans
Discount rate	3.51%	3.67%
Astoria Bank | Astoria Bank Retiree Health Care Plan
Benefit Plans
Discount rate	4.05%	4.25%
Greater Directors’ Retirement Plan | Directors' Retirement Plan
Benefit Plans
Discount rate	3.20%	3.30%
LIB Directors’ Retirement Plan | Directors' Retirement Plan
Benefit Plans
Discount rate		0.95%