Note 13 - Stockholders' Equity and Earnings per Share (Details) - Earnings per Share (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share [Abstract]
Net income	$ 35,578	$ 35,909	$ 35,084	$ 31,259	$ 32,042	$ 32,629	$ 30,066	$ 28,998	$ 137,830	$ 123,143	$ 117,438
Dividends on preferred stock						2,434	2,067	5,184		(9,685)	(16,488)
Basic EPS, income/(loss)	35,578	35,909	35,084	31,259	31,902	30,044	27,849	23,663	137,830	113,458	100,950
Basic EPS, income/(loss) (in Shares)									79,661,571	78,954,898	78,719,133
Basic EPS, income/(loss) (in Dollars per share)	$ 0.45	$ 0.45	$ 0.44	$ 0.39	$ 0.40	$ 0.38	$ 0.35	$ 0.30	$ 1.73	$ 1.44	$ 1.28
Effect of dilutive stock options (in Shares)									445,324	183,085	4,164
Diluted EPS, income/(loss)									$ 137,830	$ 113,458	$ 100,950
Diluted EPS, income/(loss) (in Shares)									80,106,895	79,137,983	78,723,297
Diluted EPS, income/(loss) (in Dollars per share)	$ 0.44	$ 0.45	$ 0.44	$ 0.39	$ 0.40	$ 0.38	$ 0.35	$ 0.30	$ 1.72	$ 1.43	$ 1.28