Benefit Plans (Details 7)	Dec. 31, 2012	Dec. 31, 2011
Astoria Federal | Pension Benefits
Assumptions used to determine the benefit obligations
Discount Rate (as a percent)	3.77%	4.44%
Rate of Compensation Increase (as a percent)		5.10%
Astoria Federal | Excess and Supplemental Benefit Plans
Assumptions used to determine the benefit obligations
Discount Rate (as a percent)	3.49%	4.16%
Rate of Compensation Increase (as a percent)		6.10%
Astoria Federal | Directors' Retirement Plan
Assumptions used to determine the benefit obligations
Discount Rate (as a percent)	3.21%	4.09%
Rate of Compensation Increase (as a percent)		4.00%
Astoria Federal | Retiree Health Care Plan
Assumptions used to determine the benefit obligations
Discount Rate (as a percent)	3.98%	4.50%
Greater | Directors' Retirement Plan
Assumptions used to determine the benefit obligations
Discount Rate (as a percent)	2.77%	3.78%
LIB | Directors' Retirement Plan
Assumptions used to determine the benefit obligations
Discount Rate (as a percent)	0.63%	1.74%