Note 1 - Summary of Significant Accounting Policies - Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income available to common shareholders	$ 96,790	$ 74,107	$ 35,688
Average common shares outstanding (in shares)	30,646	28,084	16,879
Average potential dilutive common shares (in shares)	318	126	43
Average diluted common shares (in shares)	30,964	28,210	16,922
Basic earnings per share (in dollars per share)	$ 3.16	$ 2.64	$ 2.11
Diluted earnings per share (in dollars per share)	$ 3.13	$ 2.63	$ 2.11