Benefit Plans (Details 3)	Dec. 31, 2014	Dec. 31, 2013
Astoria Bank | Pension benefits
Benefit Plans
Discount rate (as a percent)	3.77%	4.66%
Astoria Bank | Excess and supplemental benefit plans
Benefit Plans
Discount rate (as a percent)	3.60%	4.39%
Astoria Bank | Directors' retirement plan
Benefit Plans
Discount rate (as a percent)	3.47%	4.23%
Astoria Bank | Retiree health care plan
Benefit Plans
Discount rate (as a percent)	3.89%	4.80%
Greater | Directors' retirement plan
Benefit Plans
Discount rate (as a percent)	3.12%	3.64%
LIB | Directors' retirement plan
Benefit Plans
Discount rate (as a percent)	0.59%	0.50%