Stockholders' Equity (Details) (USD $)	0 Months Ended	12 Months Ended			0 Months Ended
	Jan. 07, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 19, 2013	Apr. 18, 2007
Stockholders' Equity
Par value (in dollars per share)		$ 1.00	$ 1.00
Issuance of preferred stock, series C			$ 129,796,000
Dividend reinvestment and stock purchase plan, shares of authorized and unissued reserved for the plan		1,500,000
Maximum optional cash purchases amount per month of additional shares of common stock through the dividend reinvestment and stock purchase plan	10,000
Sale of treasury stock, in shares		615,340
Proceeds from sales of treasury stock		8,121,000	0	0
Stock repurchase program approved						10,000,000
Percentage of common stock outstanding						10.00%
The remaining number of shares authorized to be purchased		8,107,300
Astoria Bank
Stockholders' Equity
Minimum notice period required for declaring dividend		30 days
Dividend paid by Astoria Bank		39,400,000
Series C Preferred Stock
Stockholders' Equity
Shares issued (in shares)			135,000		135,000
Depository shares representing percentage in non cumulative perpetual preferred stock, Series C					2.50%
Dividend rate (as a percent)		6.50%			6.50%
Par value (in dollars per share)					$ 1.00
Liquidation preference (in dollars per share)		$ 1,000			$ 1,000
Issuance of preferred stock, series C			$ 129,796,000		$ 129,800,000
Redemption price (in dollars per share)					$ 1,000
Depositary share
Stockholders' Equity
Shares issued (in shares)					5,400,000
Liquidation preference (in dollars per share)					$ 25
Redemption price (in dollars per share)					$ 25