Note 22 - Parent Company Only Financial Information - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net income, as reported	$ 14,286	$ 10,634	$ 30,435	$ 9,561	$ 11,634	$ 11,008	$ 14,834	$ 8,733	$ 64,916	$ 46,209	$ 44,239
Deferred income tax (benefit) provision									(1,540)	(5,210)	4,154
Fair value adjustments for financial assets and financial liabilities									3,434	1,841	2,568
Stock-based compensation expense									5,884	4,845	4,263
Purchases of securities available for sale									(139,186)	(313,822)	(162,830)
Proceeds from sales and calls of securities available for sale									143,819	163,158	115,294
Net cash (used in) provided by investing activities									(322,232)	(600,516)	(339,576)
Proceeds from Issuance of Subordinated Long-term Debt									73,402	0	0
Purchase of treasury stock									(9,858)	(15,605)	(18,872)
Proceeds from stock options exercised									328	145	565
Net cash provided by (used in) financing activities									273,331	563,884	282,980
Net decrease in cash and cash equivalents									(6,506)	8,098	780
Cash and cash equivalents, beginning of year				42,363				34,265	42,363	34,265	33,485
Cash and cash equivalents, end of year	35,857				42,363				35,857	42,363	34,265
Holding Company [Member]
Net income, as reported									64,916	46,209	44,239
Equity in undistributed earnings of the Bank									(45,167)	(21,884)	(24,105)
Deferred income tax (benefit) provision									(2,316)	575	17
Fair value adjustments for financial assets and financial liabilities									4,761	231	(779)
Stock-based compensation expense									5,120	4,676	4,246
Net change in operating assets and liabilities									3,318	2,174	2,088
Net cash provided by operating activities									30,632	31,981	25,706
Investment in Bank									(66,497)	0	0
Purchases of securities available for sale									0	0	(22)
Proceeds from sales and calls of securities available for sale									0	0	1,699
Net cash (used in) provided by investing activities									(66,497)	0	1,677
Proceeds from Issuance of Subordinated Long-term Debt									73,402	0	0
Purchase of treasury stock									(9,858)	(15,605)	(18,872)
Cash dividends paid									(19,689)	(18,616)	(17,852)
Proceeds from stock options exercised									328	145	565
Net cash provided by (used in) financing activities									44,183	(34,076)	(36,159)
Net decrease in cash and cash equivalents									8,318	(2,095)	(8,776)
Cash and cash equivalents, beginning of year				$ 5,654				$ 7,749	5,654	7,749	16,525
Cash and cash equivalents, end of year	$ 13,972				$ 5,654				$ 13,972	$ 5,654	$ 7,749