Note 20 - Fair Value Measurements (Details) - Fair Value of Financial Assets Measured on a Recurring Basis - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale securities
Available-for-sale securities	$ 703,347	$ 305,283
Assets held in trading accounts	6,292	6,987
US Treasury Securities [Member]
Available-for-sale securities
Available-for-sale securities	4,008	3,992
US Government Agencies Debt Securities [Member]
Available-for-sale securities
Available-for-sale securities	153,576	272,816
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities
Available-for-sale securities	502,344	1,572
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities
Available-for-sale securities	10,976	6,540
Other Securities [Member]
Available-for-sale securities
Available-for-sale securities	32,443	20,363
Other securities	32,443	20,363
Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities
Assets held in trading accounts	2,409	3,320
Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities
Assets held in trading accounts	3,883	3,667
Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Available-for-sale securities
Available-for-sale securities	4,008	3,992
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities
Available-for-sale securities	153,576	272,816
Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities
Available-for-sale securities	502,344	1,572
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities
Available-for-sale securities	10,976	6,540
Fair Value, Inputs, Level 2 [Member] | Other Securities [Member]
Available-for-sale securities
Other securities	$ 32,443	$ 20,363