Note 6 - Summary of Earnings and Weighted Average Number of Common Shares Used in Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Employee Stock Option [Member]
Dilutive effect of options (in shares)	22,545	158,387	23,406	155,972
Restricted Stock [Member]
Dilutive effect of options (in shares)				2,366
Basic (in shares)	15,266,559	13,772,873	15,091,732	13,767,248
Net income	$ 11,866	$ 12,358	$ 25,565	$ 25,600
Dividends to preferred stockholders		(2,167)		(4,335)
Net income available to common stockholders	$ 11,866	$ 10,191	$ 25,565	$ 21,265
Basic (in dollars per share)	$ 0.78	$ 0.74	$ 1.69	$ 1.54
Dilutive effect of contingent issuable stock (in shares)		450,486	97,137	410,441
Diluted (in shares)	15,289,104	14,381,746	15,212,275	14,336,027
Diluted (in dollars per share)	$ 0.78	$ 0.71	$ 1.68	$ 1.48