Consolidated Balance Sheet (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Pledged securities that can be sold or repledged	$ 1,611,069	$ 1,631,267
Investment securities, available for sale, amortized cost	10,425,720	8,919,324
Investment securities, held to maturity, fair value	3,411,834	3,538,282
Other, fair value	$ 328,958	$ 328,742
Preferred stock, par value	$ 1.00	$ 1.00
Preferred stock, shares authorized	1,000,000	1,000,000
Common stock, par value	$ 0.50	$ 0.50
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	132,909,718	132,312,931
Common stock issuable, shares	36,360	41,330
Series A and Series C [Member]
Preferred stock, shares issued	731,500	731,500
Preferred stock, shares outstanding	731,500	731,500
Preferred stock, liquidation preference per share	$ 1,000	$ 1,000
Series D Preferred Stock [Member]
Preferred stock, shares issued	50,000	50,000
Preferred stock, shares outstanding	50,000	50,000
Preferred stock, liquidation preference per share	$ 10,000	$ 10,000