Note 10 - Borrowed Funds (Details) - Comparative Data for Securities Sold Under Agreements to Repurchase (Securities Sold under Agreements to Repurchase [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Securities Sold under Agreements to Repurchase [Member]
Note 10 - Borrowed Funds (Details) - Comparative Data for Securities Sold Under Agreements to Repurchase [Line Items]
Average amount outstanding during the year (1)	$ 629,315	[1]	$ 972,329	[1]	$ 1,361,475	[1]
Maximum amount outstanding at month-end (2)	700,000	[2]	1,200,000	[2]	1,400,000	[2]
Balance, December 31	$ 450,000		$ 800,000		$ 1,250,000
Rate, December 31	3.85%		3.87%		3.84%
Weighted average interest rate for the year	3.92%		3.88%		4.09%

[1] Average balances were computed using daily averages.

[2] Highest month-end balances were January 2014, January 2013, and January 2012.