Note 5 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Less than 12 months, fair value	$ 11,484	$ 118,916
Less than 12 months, gross unrealized losses	123	2,036
12 months or greater, fair value	143,026	97,987
12 months or greater, gross unrealized losses	2,197	3,063
Total, fair value	154,510	216,903
Total, gross unrealized losses	2,320	5,099
US Government Agencies Debt Securities [Member]
Less than 12 months, fair value		4,399
Less than 12 months, gross unrealized losses		28
12 months or greater, fair value	4,347	4,610
12 months or greater, gross unrealized losses	37	116
Total, fair value	4,347	9,009
Total, gross unrealized losses	37	144
Corporate Debt Securities [Member]
Less than 12 months, fair value	3,938	6,274
Less than 12 months, gross unrealized losses	92	260
12 months or greater, fair value	2,360	2,324
12 months or greater, gross unrealized losses	140	176
Total, fair value	6,298	8,598
Total, gross unrealized losses	232	436
Collateralized Mortgage Backed Securities [Member]
Less than 12 months, fair value	17	67,770
Less than 12 months, gross unrealized losses		1,264
12 months or greater, fair value	109,574	61,271
12 months or greater, gross unrealized losses	1,816	2,300
Total, fair value	109,591	129,041
Total, gross unrealized losses	1,816	3,564
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	7,529	40,473
Less than 12 months, gross unrealized losses	31	484
12 months or greater, fair value	26,745	29,782
12 months or greater, gross unrealized losses	204	471
Total, fair value	34,274	70,255
Total, gross unrealized losses	$ 235	$ 955