Note 3 - Investment Securities - Securities in a Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Available-for-sale, less than 12 months, fair value	$ 58,440	$ 142,723
Available-for-sale, less than 12 months, unrealized losses	(260)	(2,936)
Available-for-sale, 12 months or more, fair value	51,641	12,625
Available-for-sale, 12 months or more, unrealized losses	(763)	(368)
Held-to-maturity, less than 12 months, fair value	12,860	22,361
Held-to-maturity, less than 12 months, unrealized losses	(85)	(416)
Held-to-maturity, 12 months or more, fair value	5,311
Held-to-maturity, 12 months or more, unrealized losses	(58)
Residential Mortgage Backed Securities [Member]
Available-for-sale, less than 12 months, fair value	38,784	85,741
Available-for-sale, less than 12 months, unrealized losses	(115)	(1,976)
Available-for-sale, 12 months or more, fair value	14,350	1,904
Available-for-sale, 12 months or more, unrealized losses	(203)	(27)
Commercial Mortgage Backed Securities [Member]
Available-for-sale, less than 12 months, fair value	19,576	54,475
Available-for-sale, less than 12 months, unrealized losses	(145)	(946)
Available-for-sale, 12 months or more, fair value	37,291	10,721
Available-for-sale, 12 months or more, unrealized losses	(560)	(341)
Held-to-maturity, less than 12 months, fair value	9,643	12,776
Held-to-maturity, less than 12 months, unrealized losses	(58)	(148)
Held-to-maturity, 12 months or more, fair value	423
Held-to-maturity, 12 months or more, unrealized losses	(3)
US Government Agencies Debt Securities [Member]
Available-for-sale, less than 12 months, fair value		1,993
Available-for-sale, less than 12 months, unrealized losses		(7)
Available-for-sale, 12 months or more, fair value
Available-for-sale, 12 months or more, unrealized losses
Held-to-maturity, less than 12 months, fair value	3,217	7,957
Held-to-maturity, less than 12 months, unrealized losses	(27)	(222)
Held-to-maturity, 12 months or more, fair value	4,345
Held-to-maturity, 12 months or more, unrealized losses	(52)
US Treasury Securities [Member]
Available-for-sale, less than 12 months, fair value	80	80
Available-for-sale, less than 12 months, unrealized losses
Available-for-sale, 12 months or more, fair value
Available-for-sale, 12 months or more, unrealized losses
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale, less than 12 months, fair value		434
Available-for-sale, less than 12 months, unrealized losses		(7)
Available-for-sale, 12 months or more, fair value
Available-for-sale, 12 months or more, unrealized losses
Held-to-maturity, less than 12 months, fair value		1,628
Held-to-maturity, less than 12 months, unrealized losses		(46)
Held-to-maturity, 12 months or more, fair value	543
Held-to-maturity, 12 months or more, unrealized losses	$ (3)