Benefit Plans (Details 9) (Pension benefits, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Benefit Plans
Pension plan assets	$ 187,074	$ 189,367	$ 160,683
Astoria Bank | Recurring basis
Benefit Plans
Pension plan assets	187,074	189,367
Astoria Bank | Recurring basis | Level 1
Benefit Plans
Pension plan assets	12,408	12,691
Astoria Bank | Recurring basis | Level 2
Benefit Plans
Pension plan assets	162,808	170,377
Astoria Bank | Recurring basis | Level 3
Benefit Plans
Pension plan assets	11,858	6,299
Astoria Bank | Cash and cash equivalents | Recurring basis
Benefit Plans
Pension plan assets	4	4
Astoria Bank | Cash and cash equivalents | Recurring basis | Level 1
Benefit Plans
Pension plan assets	4	4
Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis
Benefit Plans
Pension plan assets	162,808	170,377
Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis | Level 2
Benefit Plans
Pension plan assets	162,808	170,377
Astoria Bank | Astoria Financial Corporation common stock | Recurring basis
Benefit Plans
Pension plan assets	12,404	12,687
Astoria Bank | Astoria Financial Corporation common stock | Recurring basis | Level 1
Benefit Plans
Pension plan assets	12,404	12,687
Astoria Bank | PRIAC Guaranteed Deposit Account | Recurring basis
Benefit Plans
Pension plan assets	11,858	6,299
Astoria Bank | PRIAC Guaranteed Deposit Account | Recurring basis | Level 3
Benefit Plans
Pension plan assets	$ 11,858	$ 6,299