Condensed Parent Company Only Financial Statements (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 95,916	$ 66,593	$ 53,091
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred costs	9,021	15,794	16,762
Net cash provided by operating activities	134,076	232,664	187,413
Cash flows from investing activities:
Redemption of Astoria Capital Trust I common securities	0	3,866	0
Net cash provided by investing activities	197,948	488,662	377,632
Cash flows from financing activities:
Proceeds from borrowings with original terms greater than three months	0	0	950,000
Repayments of borrowings with original terms greater than three months	(150,000)	(553,866)	(1,144,000)
Cash payments for debt issuance costs	0	0	(2,653)
Cash payments for preferred stock issuance costs	0	(5,204)	0
Cash dividends paid to stockholders	(24,643)	(20,688)	(24,104)
Net cash used in financing activities	(310,789)	(720,849)	(576,276)
Net increase (decrease) in cash and cash equivalents	21,235	477	(11,231)
Cash and cash equivalents at beginning of year	121,950	121,473	132,704
Cash and cash equivalents at end of year	143,185	121,950	121,473
Supplemental disclosure:
Interest paid	150,026	180,871	258,503
Astoria Financial Corporation
Cash flows from operating activities:
Net income	95,916	66,593	53,091
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiaries	(67,852)	(39,528)	(35,015)
Amortization of deferred costs	531	531	837
(Increase) decrease in other assets, net of other liabilities and amounts due to subsidiaries	(484)	(998)	846
Net cash provided by operating activities	28,111	26,598	19,759
Cash flows from investing activities:
Principal payments on ESOP loans receivable		5,908	6,235
Redemption of Astoria Capital Trust I common securities		3,866
Net cash provided by investing activities		9,774	6,235
Cash flows from financing activities:
Proceeds from borrowings with original terms greater than three months			250,000
Repayments of borrowings with original terms greater than three months		(128,866)	(250,000)
Cash payments for debt issuance costs			(2,653)
Proceeds from issuance of common and preferred stock	8,121	135,000
Cash payments for preferred stock issuance costs		(5,204)
Cash dividends paid to stockholders	(24,643)	(20,688)	(24,104)
Net tax benefit excess (shortfall) from stock-based compensation	192	(800)	(4,123)
Net cash used in financing activities	(16,330)	(20,558)	(30,880)
Net increase (decrease) in cash and cash equivalents	11,781	15,814	(4,886)
Cash and cash equivalents at beginning of year	63,418	47,604	52,490
Cash and cash equivalents at end of year	75,199	63,418	47,604
Supplemental disclosure:
Interest paid	$ 12,500	$ 18,898	$ 31,535