Note 3 - Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Less than 12 months, fair value	$ 6,500	$ 31,421
Less than 12 months, unrealized loss	(19)	(437)
12 months or more, fair value	51,296	50,394
12 months or more, unrealized loss	(1,004)	(1,570)
Total, fair value	57,796	81,815
Total, unrealized loss	(1,023)	(2,007)
US Treasury and Government [Member]
Less than 12 months, fair value
Less than 12 months, unrealized loss
12 months or more, fair value	4,472	4,445
12 months or more, unrealized loss	(57)	(87)
Total, fair value	4,472	4,445
Total, unrealized loss	(57)	(87)
US Government Agencies Debt Securities [Member]
Less than 12 months, fair value		2,472
Less than 12 months, unrealized loss		(30)
12 months or more, fair value	10,434	10,337
12 months or more, unrealized loss	(164)	(269)
Total, fair value	10,434	12,809
Total, unrealized loss	(164)	(299)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Less than 12 months, fair value	3,922	19,483
Less than 12 months, unrealized loss	(5)	(297)
12 months or more, fair value	15,066	7,693
12 months or more, unrealized loss	(137)	(193)
Total, fair value	18,988	27,176
Total, unrealized loss	(142)	(490)
Collateralized Mortgage Obligations [Member]
Less than 12 months, fair value	1,784	1,443
Less than 12 months, unrealized loss	(14)	(5)
12 months or more, fair value	16,392	15,388
12 months or more, unrealized loss	(599)	(805)
Total, fair value	18,176	16,831
Total, unrealized loss	(613)	(810)
US States and Political Subdivisions Debt Securities [Member]
Less than 12 months, fair value	794	7,061
Less than 12 months, unrealized loss		(67)
12 months or more, fair value	1,959	10,083
12 months or more, unrealized loss	(15)	(157)
Total, fair value	2,753	17,144
Total, unrealized loss	(15)	(224)
Corporate Debt Securities [Member]
Less than 12 months, fair value		962
Less than 12 months, unrealized loss		(38)
12 months or more, fair value	2,973	2,448
12 months or more, unrealized loss	(32)	(59)
Total, fair value	2,973	3,410
Total, unrealized loss	$ (32)	$ (97)