Note 9 - Securities Sold Under Agreements to Repurchase (Detail) (USD $)	Sep. 30, 2012	Jul. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	May 31, 2011	Sep. 30, 2012 Modifications [Member]	Jun. 30, 2012 Modifications [Member]	Sep. 30, 2012 First Agreement Modified [Member]	Sep. 30, 2012 Second Agreement Modified [Member]	Sep. 30, 2012 Callable Securities [Member]	Sep. 30, 2012 Securities Sold Under Agreements to Repurchase Minimum [Member]	May 31, 2018 Securities Sold Under Agreements to Repurchase Maximum Initial Rate [Member]	Sep. 30, 2012 Securities Sold Under Agreements to Repurchase Maximum Initial Rate [Member]	May 31, 2018 Securities Sold Under Agreements to Repurchase Minimum Interest Rate [Member]	May 31, 2018 Minimum [Member]	Sep. 30, 2012 Minimum [Member]	May 31, 2018 Maximum [Member]	Sep. 30, 2012 Maximum [Member]
Securities Sold under Agreements to Repurchase (in Dollars)	$ 1,350,000,000			$ 1,400,000,000		$ 50,000,000	$ 100,000,000			$ 1,150,000,000
Weighted Average Rate Of Securities Sold Under Agreements	3.89%			4.14%
Prepaid Security Sold Under Repurchase Agreement (in Dollars)		50,000,000			50,000,000
Rate of Prepaid Security Sold Under Repurchase Agreements		4.43%			4.83%
Prepayment Penalty Security Sold Under Agreements To Repurchase (in Dollars)		3,500,000			1,700,000
Extended Term on Securities Sold Under Agreements to Resell			4 years					2 years	3 years
Adjustment to Rate on Securities Sold Under Agreements to Repurchase (in Basis Points)	1.85%		1.50%
Number Of Floating-To-Fixed Rate Agreements	9
Total Floating To Fixed Rate (in Dollars)	500,000,000
Initial Floating Rate Period On Floating-To-Fixed Rate Agreements, Months																6
Initial Floating Rate Period On Floating-To-Fixed Rate Agreements Years																		1
LIBOR Minus Hundred Basis Point	100
LIBOR Minus Three Hundred and Forty Basis Points	three-month LIBOR minus 340 basis points
Current Lowest Rate Long Term Initial Floating To Fix Security Sold Under Agreements To Repurchase																4.35%
Current Highest Rate Long Term Initial Floating To Fix Security Sold Under Agreements To Repurchase																		5.07%
Number Of Fixed-To-Floating Security Sold Under Agreements To Repurchase	13
Total Fixed To Floating Rate Agreements (in Dollars)	650,000,000
Debt Instrument, Interest Rate, Stated Percentage											1.00%		3.50%
Initial Fixed Rate Period																6		18
Remainder Of Long Term Securities	7
Debt Instrument Interest Float Rate At Stated Percentage Minus 3 Mons Libor												8.00%
Debt Instrument, Basis Spread on Variable Rate															3.25%		3.79%
Long-term Debt, Weighted Average Interest Rate														0.00%
Pledged Mortgage Backed Securities for Securities Sold Under Agreements to Repurchase (in Dollars)	$ 1,500,000,000			$ 1,600,000,000