Merger Agreement with New York Community Bancorp, Inc. (Details) $ / shares in Units, $ in Millions	Oct. 28, 2015 USD ($) $ / shares shares	Jun. 30, 2016 $ / shares shares	Dec. 31, 2015 $ / shares shares
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)		$ 0.01	$ 0.01
Preferred stock, par value (in dollars per share)		$ 1.00	$ 1.00
Common stock, shares authorized (in shares) | shares		200,000,000	200,000,000
Contract termination fee | $	$ 69.5
Series C Preferred Stock
Business Acquisition [Line Items]
Dividend rate	6.50%
Preferred stock, par value (in dollars per share)	$ 1.00
Liquidation preference (in dollars per share)	$ 1,000
New York Community Bancorp, Inc | Astoria Financial Corporation
Business Acquisition [Line Items]
Conversion of preferred shares of acquiree to acquirer	1
Common stock, par value (in dollars per share)	$ 0.01
Share price for acquisition (in dollars per share)	$ 0.50
New York Community Bancorp, Inc | Astoria Financial Corporation | Minimum
Business Acquisition [Line Items]
Common stock, shares authorized (in shares) | shares	600,000,000
New York Community Bancorp, Inc | Astoria Financial Corporation | Maximum
Business Acquisition [Line Items]
Common stock, shares authorized (in shares) | shares	900,000,000
New York Community Bancorp, Inc | Astoria Financial Corporation | Series A Preferred Stock
Business Acquisition [Line Items]
Dividend rate	6.50%
Preferred stock, par value (in dollars per share)	$ 0.01
Liquidation preference (in dollars per share)	$ 1,000