Note 4 - Investment Securities (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Proceeds from Sale of Mortgage Backed Securities (MBS) categorized as Available-for-sale	$ 501,100,000	$ 759,700,000	$ 1,040,000,000
Proceeds from Maturities, Prepayments and Calls of Mortgage Backed Securities (MBS)	118,100,000	108,400,000	308,200,000
Proceeds From Sales and Repayments of Other Investment Securities	61,000,000	525,000,000	65,100,000
Proceeds From Maturities Repayments And Calls Of Held For Investment	552,100,000	435,000,000	2,880,000,000
Realized Gain From Sale and Call of Investment Securities	18,600,000	21,100,000	19,300,000
Realized Loss From Sale and Call of Investment Securities	607,000	0	67,000
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Other, Percentage of Nonperforming Assets	16.90%
Percentage of Unrealized Losses for Securities with Unrealized Losses for Less Than Twelve Months	2.40%
Percentage of Unrealized Losses for Securities with Unrealized Losses for Greater than Twelve Months	4.40%
Pledged Investment Securities	$ 1,450,000,000	$ 1,680,000,000
Twelve Months or Longer [Member]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	34
Less than Twelve Months [Member]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	7