CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
CONSOLIDATED BALANCE SHEETS
Securities available-for-sale, cost (in dollars)	$ 7,610,489	$ 9,057,238
Securities held-to-maturity, fair value (in dollars)	1,434,836	1,446,599
Other real estate owned, covered by FDIC loss share (in dollars)	$ 43,751	$ 58,276
Preferred stock, par value (in dollars per share)	$ 1.00	$ 1.00
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	175,000	175,000
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	54,133,065	53,885,886
Treasury shares	495,447	669,454