Benefit Plans - Assumptions Used to Determine Net Periodic (Benefit) Cost (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Astoria Bank | Pension Benefits
Assumptions used to determine net periodic cost
Discount Rate	3.77%	4.66%
Expected Return on Plan Assets	8.00%	8.00%
Astoria Bank | Excess and supplemental benefit plans
Assumptions used to determine net periodic cost
Discount Rate	3.60%	4.39%
Astoria Bank | Directors' retirement plan
Assumptions used to determine net periodic cost
Discount Rate	3.47%	4.23%
Astoria Bank | Retiree health care plan
Assumptions used to determine net periodic cost
Discount Rate	3.89%	4.80%
Greater | Directors' retirement plan
Assumptions used to determine net periodic cost
Discount Rate	3.12%	3.64%
LIB | Directors' retirement plan
Assumptions used to determine net periodic cost
Discount Rate	0.59%	0.50%