Note 10 - Borrowed Funds (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2005	Dec. 31, 2004	May 31, 2011
Federal Funds Purchased		$ 27,000
Securities Sold under Agreements to Repurchase	1,250,000,000	1,400,000,000
Prepaid Security Sold Under Repurchase Agreement	150,000,000	50,000,000
Rate of Prepaid Security Sold Under Repurchase Agreements	4.43%	4.83%
Prepayment Penalty Security Sold Under Agreements To Repurchase	9,400,000					1,700,000
Average Rate Reduction on Modified Repurchase Agreements (in Basis Points)	1.68%
Number Of Fixed-To-Floating Security Sold Under Agreements To Repurchase	13
Total Fixed To Floating Rate Agreements	650,000,000
Minimum Initial Fixed Rate	1.00%
Maximum Initial Fixed Rate	3.50%
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	0.00%
Advances from Federal Home Loan Banks	146,200,000	225,000,000
Federal Home Loan Bank Prepaid Advances	100,000,000	450,000,000
Weighted Average Rate for Prepaying Federal Home Loan Bank Advances	4.60%	4.39%
Prepayment Fees on Advances, Net	2,800,000	18,500,000
Other Borrowings		880,000
Weighted Average Rate for Borrowing From Other Financial Institutions		0.55%
Threshold for Deferred Bonus				225,000
AmountOfDeferredBonusAccruedInOtherLiabilities					610,000
Accrued Interest On Deferred Bonus	7.00%
Debt Instrument Basis Spread (in Basis Points)	2.75%
Interest Expense, Other	71,000	67,000	62,000
Accrued Bonuses	1,100,000	995,000
Federal Funds Purchased [Member]
Debt Instrument, Interest Rate, Stated Percentage		1.29%
Securities Sold under Agreements to Repurchase [Member]
Line of Credit Facility, Interest Rate at Period End	3.84%	4.14%	4.18%
Investment Securities Pledged As Collateral	1,400,000,000	1,600,000,000
Terms Modified in Current Year [Member]
Securities Sold under Agreements to Repurchase						200,000,000
Floating to Fixed Rate Agreements Totaling $400 Million [Member] | Minimum [Member]
Debt Instrument, Interest Rate, Stated Percentage	4.52%
Floating to Fixed Rate Agreements Totaling $400 Million [Member] | Maximum [Member]
Debt Instrument, Interest Rate, Stated Percentage	5.07%
Floating to Fixed Rate Agreements Totaling $400 Million [Member]
Number Of Floating-To-Fixed Rate Agreements	7
Total Floating To Fixed Rate	400,000,000
LIBOR Minus Three Hundred and Forty Basis Points	LIBOR minus 340
Federal Home Loan Bank Advances [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Weighted Average Interest Rate	0.44%	2.08%
Floating to Fixed Rate Agreements Totaling $400 Million [Member]
LIBOR Minus Hundred Basis Point	LIBOR minus 200
Callable Securities [Member]
Securities Sold under Agreements to Repurchase	$ 1,050,000,000
Minimum [Member]
Debt Instrument, Interest Rate, Stated Percentage	8.00%
Debt Instrument, Basis Spread on Variable Rate (in Basis Points)	3.25%
Maximum [Member]
Debt Instrument, Basis Spread on Variable Rate (in Basis Points)	3.79%