Benefit Plans - Schedule of Carrying Values of Assets (Details) - Pension Benefits - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Benefit Plans
Total	$ 182,770	$ 180,387	$ 187,074
Astoria Bank | Recurring basis
Benefit Plans
Total	182,770	180,387
Astoria Bank | Recurring basis | Level 1
Benefit Plans
Total	173,624	170,099
Astoria Bank | Recurring basis | Level 2
Benefit Plans
Total	0	0
Astoria Bank | Recurring basis | Level 3
Benefit Plans
Total	9,146	10,288
Astoria Bank | Cash and cash equivalents | Recurring basis
Benefit Plans
Total	4	4
Astoria Bank | Cash and cash equivalents | Recurring basis | Level 1
Benefit Plans
Total	4	4
Astoria Bank | Cash and cash equivalents | Recurring basis | Level 2
Benefit Plans
Total	0	0
Astoria Bank | Cash and cash equivalents | Recurring basis | Level 3
Benefit Plans
Total	0	0
Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis
Benefit Plans
Total	155,925	155,215
Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis | Level 1
Benefit Plans
Total	155,925	155,215
Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis | Level 2
Benefit Plans
Total	0	0
Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis | Level 3
Benefit Plans
Total	$ 0	$ 0
Astoria Bank | PRIAC Pooled Separate Accounts | Debt securities | Recurring basis
Benefit Plans
Components of PRIAC Pooled Separate Accounts (as a percent)	34.00%	33.00%
Astoria Bank | Astoria Financial Corporation common stock | Recurring basis
Benefit Plans
Total	$ 17,695	$ 14,880
Astoria Bank | Astoria Financial Corporation common stock | Recurring basis | Level 1
Benefit Plans
Total	17,695	14,880
Astoria Bank | Astoria Financial Corporation common stock | Recurring basis | Level 2
Benefit Plans
Total	0	0
Astoria Bank | Astoria Financial Corporation common stock | Recurring basis | Level 3
Benefit Plans
Total	0	0
Astoria Bank | PRIAC Guaranteed Deposit Account | Recurring basis
Benefit Plans
Total	9,146	10,288
Astoria Bank | PRIAC Guaranteed Deposit Account | Recurring basis | Level 1
Benefit Plans
Total	0	0
Astoria Bank | PRIAC Guaranteed Deposit Account | Recurring basis | Level 2
Benefit Plans
Total	0	0
Astoria Bank | PRIAC Guaranteed Deposit Account | Recurring basis | Level 3
Benefit Plans
Total	$ 9,146	$ 10,288
Large-cap equity securities | Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis
Benefit Plans
Components of PRIAC Pooled Separate Accounts (as a percent)	42.00%	44.00%
Small-cap equity securities | Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis
Benefit Plans
Components of PRIAC Pooled Separate Accounts (as a percent)	8.00%	7.00%
Mid-cap equity securities | Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis
Benefit Plans
Components of PRIAC Pooled Separate Accounts (as a percent)	6.00%	5.00%
International equities | Astoria Bank | PRIAC Pooled Separate Accounts | Recurring basis
Benefit Plans
Components of PRIAC Pooled Separate Accounts (as a percent)	10.00%	11.00%