Merger Agreement with New York Community Bancorp, Inc. (Details) $ / shares in Units, $ in Millions			12 Months Ended
	Oct. 28, 2015 USD ($) $ / shares shares	Mar. 19, 2013 $ / shares	Dec. 31, 2015 $ / shares shares	Dec. 31, 2014 $ / shares shares
Business Acquisition [Line Items]
Common stock, shares authorized | shares			200,000,000	200,000,000
Par value (in dollars per share)			$ 1.00	$ 1.00
Contract termination fee | $	$ 69.5
Series C Preferred Stock
Business Acquisition [Line Items]
Dividend rate	6.50%	6.50%	6.50%
Par value (in dollars per share)	$ 1.00	$ 1.00
Liquidation preference (in dollars per share)	1,000	$ 1,000	$ 1,000
Astoria | NYCB
Business Acquisition [Line Items]
Share price for acquisition (in dollars per share)	0.01
Equity interest issued or issuable for each share	$ 0.50
Conversion of preferred shares of acquiree to acquirer	1
Astoria | NYCB | Minimum
Business Acquisition [Line Items]
Common stock, shares authorized | shares	600,000,000
Astoria | NYCB | Maximum
Business Acquisition [Line Items]
Common stock, shares authorized | shares	900,000,000
Astoria | Series A Preferred Stock | NYCB
Business Acquisition [Line Items]
Dividend rate	6.50%
Par value (in dollars per share)	$ 0.01
Liquidation preference (in dollars per share)	$ 1,000