Note 20 - Quarterly Financial Data (Unaudited) - Summary of Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income	$ 19,409		$ 17,922		$ 17,331		$ 16,187		$ 14,636		$ 13,620		$ 13,209		$ 12,762		$ 70,849	$ 54,227	$ 45,436
Interest expense	2,542		2,210		2,064		1,968		1,946		1,834		1,612		1,471		8,784	6,863	5,381
Interest income	16,867		15,712		15,267		14,219		12,690		11,786		11,597		11,291		62,065	47,364	40,055
Provision for loan losses	400				500						607		650		300		900	1,557	500
Non-interest income	5,012		5,778		4,969		4,338		4,727		5,142		3,031		2,412		20,097	15,312	9,943
Non-interest expense	21,622		19,165		17,685		16,804		15,970		15,013		12,967		12,343		75,276	56,293	47,091
Benefit for income taxes	(2,881)		4		(8)		(34)		(50)		(32)		(12)		(25)		(2,919)	(119)	(26)
Net income	$ 2,738		$ 2,321		$ 2,059		$ 1,787		$ 1,497		$ 1,340		$ 1,023		$ 1,085		$ 8,905	$ 4,945	$ 2,433
Basic (in dollars per share)	$ 0.05	[1]	$ 0.04	[1]	$ 0.04	[1]	$ 0.03	[1]	$ 0.03	[1]	$ 0.04	[1]	$ 0.03	[1]	$ 0.03	[1]	$ 0.16	$ 0.13	$ 0.06
Diluted (in dollars per share)	$ 0.05	[1]	$ 0.04	[1]	$ 0.04	[1]	$ 0.03	[1]	$ 0.03	[1]	$ 0.03	[1]	$ 0.03	[1]	$ 0.03	[1]	$ 0.15	$ 0.12	$ 0.06

[1] Quarterly net income per share does not add to full year net income per share due to rounding.