Note 13 - Stockholders' Equity and Earnings Per Share (Details) - Earnings per Share - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net income	$ 41,446	$ 38,483	$ 45,200	$ 35,980	$ 35,578	$ 35,909	$ 35,084	$ 31,259	$ 161,109	$ 137,830	$ 123,143
Dividends on preferred stock											(9,685)
Basic EPS, income									$ 161,109	$ 137,830	$ 113,458
Basic EPS, income (in Shares)									80,563,577	79,661,571	78,954,898
Basic EPS, income (in Dollars per share)	$ 0.51	$ 0.47	$ 0.57	$ 0.45	$ 0.45	$ 0.45	$ 0.44	$ 0.39	$ 2.00	$ 1.73	$ 1.44
Effect of dilutive stock options (in Shares)									731,219	445,324	183,085
Diluted EPS, income									$ 161,109	$ 137,830	$ 113,458
Diluted EPS, income (in Shares)									81,294,796	80,106,895	79,137,983
Diluted EPS, income (in Dollars per share)	$ 0.51	$ 0.47	$ 0.56	$ 0.45	$ 0.44	$ 0.45	$ 0.44	$ 0.39	$ 1.98	$ 1.72	$ 1.43