Note 6 - Investment Securities (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Investment Securities	$ 2,200,000,000		$ 2,100,000,000
Held-to-maturity Securities, Transferred Security, at Carrying Value	722,500,000
Held-to-maturity Securities, Transferred Security, Unrealized Gain (Loss)	40,500,000
Proceeds from Sale of Mortgage Backed Securities (MBS) categorized as Available-for-sale	0	117,600,000
Proceeds from Maturities, Prepayments and Calls of Mortgage Backed Securities (MBS)	98,400,000	94,200,000
Proceeds From Sales and Repayments of Other Investment Securities	320,200,000	30,600,000
Proceeds From Maturities Repayments And Calls Of Held For Investment	10,100,000	200,000,000
Realized Gain From Sale and Call of Investment Securities	6,300,000	2,800,000
Realized Loss From Sale and Call of Investment Securities	0	595,000
Temporarily Impaired Securities As Percentage of Investment Securities	24.20%
Percentage of Unrealized Losses for Securities with Unrealized Losses for Less Than Twelve Months			0.50%
Percentage of Unrealized Losses for Securities with Unrealized Losses for Greater than Twelve Months			4.40%
Pledged Investment Securities	$ 1,360,000,000		$ 1,450,000,000
Corporate Bonds Issued By Financial Institutions [Member]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	27