Note 3 - Securities - Securities in a Continuous Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Securities in a Continuours Loss Position, Less Than 12 Months, Fair Value	$ 295,295	$ 96,678
Securities in a Continuours Loss Position, Less Than 12 Months, Unrealized Loss	7,232	2,116
Securities in a Continuours Loss Position, 12 Months or More, Fair Value	2,475	95,447
Securities in a Continuours Loss Position, 12 Months or More, Unrealized Loss	178	3,698
US Government Agencies Debt Securities [Member]
Securities in a Continuours Loss Position, Less Than 12 Months, Fair Value	260,150	88,255
Securities in a Continuours Loss Position, Less Than 12 Months, Unrealized Loss	6,161	1,800
Securities in a Continuours Loss Position, 12 Months or More, Fair Value	996	84,959
Securities in a Continuours Loss Position, 12 Months or More, Unrealized Loss	4	3,329
US States and Political Subdivisions Debt Securities [Member]
Securities in a Continuours Loss Position, Less Than 12 Months, Fair Value	31,257	3,449
Securities in a Continuours Loss Position, Less Than 12 Months, Unrealized Loss	934	24
Securities in a Continuours Loss Position, 12 Months or More, Fair Value	1,316	10,161
Securities in a Continuours Loss Position, 12 Months or More, Unrealized Loss	148	306
Corporate Debt Securities [Member]
Securities in a Continuours Loss Position, Less Than 12 Months, Fair Value	3,888	4,974
Securities in a Continuours Loss Position, Less Than 12 Months, Unrealized Loss	137	292
Securities in a Continuours Loss Position, 12 Months or More, Fair Value	0	200
Securities in a Continuours Loss Position, 12 Months or More, Unrealized Loss	0	1
Other Securities [Member]
Securities in a Continuours Loss Position, Less Than 12 Months, Fair Value	0	0
Securities in a Continuours Loss Position, Less Than 12 Months, Unrealized Loss	0	0
Securities in a Continuours Loss Position, 12 Months or More, Fair Value	163	127
Securities in a Continuours Loss Position, 12 Months or More, Unrealized Loss	$ 26	$ 62