Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Series A Preferred Stock [Member]	Dec. 31, 2011 Series A Preferred Stock [Member]	Dec. 31, 2012 Series E Preferred Stock [Member]	Dec. 31, 2011 Series E Preferred Stock [Member]
Securities held-to-maturity ,fair value	$ 3,264,718	$ 3,130,546
Preferred stock, par value			$ 0.01	$ 0.01	$ 0.01	$ 0.01
Preferred stock, shares authorized			3,000,000	3,000,000	3,000,000	3,000,000
Preferred stock, shares issued			28,939	28,939	5,060	5,060
Preferred stock, shares outstanding			28,939	28,939	5,060	5,060
Common stock par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	90,735,596	90,709,350
Treasury stock ,shares	5,772,006	3,493,915