Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Security held-to-maturity, fair value	$ 3,961,534	$ 3,948,706
Preferred stock, par value (in usd per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	3,000,000	3,000,000
Common stock par value (in usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	93,651,601	93,623,090
Treasury stock, shares	2,090,409	3,241,555
Series A Preferred Stock [Member]
Preferred stock, shares issued	0	28,939
Preferred Stock, Shares Outstanding	0	28,939
Series E Preferred Stock [Member]
Preferred stock, shares issued	5,060	5,060
Preferred Stock, Shares Outstanding	5,060	5,060