Note 24 - Quarterly Results of Operations (Unaudited) (Details) - Selected Unaudited Quarterly Financial Data - 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
Selected Unaudited Quarterly Financial Data [Abstract]
Interest income	$ 119,519	$ 116,867	$ 112,386	$ 104,934	$ 106,043	$ 106,335	$ 105,062	$ 101,207
Interest expense	20,103	19,221	17,632	17,008	18,292	19,580	19,445	18,549	$ 73,964	$ 75,866	$ 82,300
Net interest income	99,416	97,646	94,754	87,926	87,751	86,755	85,617	82,658	379,742	342,781	324,696
Reversal for credit losses	(3,000)	(1,250)	(2,150)	(5,000)	(2,000)	(5,100)	(3,700)		(11,400)	(11,172)	(3,000)
Net-interest income after provision for loan losses	102,416	98,896	96,904	92,926	89,751	91,855	89,317	82,658	391,142	353,581	327,696
Non-interest income	9,350	9,156	5,619	8,549	7,973	8,974	9,021	14,559	32,674	40,527	60,307
Non-interest expense	53,533	57,471	47,585	44,131	41,125	42,607	42,513	48,068	202,720	174,313	193,833
Income before income tax expense	58,233	50,581	54,938	57,344	56,599	58,222	55,825	49,149	221,096	219,795	194,170
Income tax expense	16,787	12,098	9,738	21,364	21,021	22,313	20,741	17,890	59,987	81,965	70,435
Net income	$ 41,446	$ 38,483	$ 45,200	$ 35,980	$ 35,578	$ 35,909	$ 35,084	$ 31,259	$ 161,109	$ 137,830	$ 123,143
Net income per common share
Basic (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
Diluted (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