Note 3 - Securities - Securities Available-for-sale With Unrealized Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Less than 12 Months - Fair Value	$ 54,619	$ 44,331
Less than 12 Months - Unrealized Loss	(1,544)	(531)
12 Months or More - Fair Value	33,655	38,326
12 Months or More - Unrealized Loss	(1,866)	(1,099)
Fair Value	88,274	82,657
Unrealized Loss	(3,410)	(1,630)
US Government-sponsored Enterprises Debt Securities [Member]
Less than 12 Months - Fair Value	5,843	6,910
Less than 12 Months - Unrealized Loss	(145)	(97)
12 Months or More - Fair Value	4,779	6,563
12 Months or More - Unrealized Loss	(161)	(52)
Fair Value	10,622	13,473
Unrealized Loss	(306)	(149)
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Less than 12 Months - Fair Value	48,776	37,421
Less than 12 Months - Unrealized Loss	(1,399)	(434)
12 Months or More - Fair Value	28,876	31,763
12 Months or More - Unrealized Loss	(1,705)	(1,047)
Fair Value	77,652	69,184
Unrealized Loss	$ (3,104)	$ (1,481)