Note 22 - Parent Company Only Financial Information (Details) - Condensed Statements of Cash Flows for the Holding Company: (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net income	$ 44,239	$ 37,752	$ 34,331
Adjustments to reconcile net income to net cash provided by operating activities:
Net gain on sale of securities	(2,875)	(3,021)	(47)
Deferred income tax (benefit) provision	4,154	(682)	(804)
Fair value adjustments for financial assets and financial liabilities	2,568	2,521	(55)
Stock based compensation expense	4,263	3,412	3,260
Net cash provided by operating activities	57,376	74,435	71,097
Investing activities:
Purchases of securities available for sale	(162,830)	(458,596)	(311,654)
Proceeds from sales and calls of securities available for sale	115,294	194,009	12,637
Net cash provided by (used in) investing activities	(339,576)	(326,024)	(197,988)
Financing activities:
Purchase of treasury stock	(18,872)	(14,151)	(5,551)
Cash dividends paid	(17,852)	(15,618)	(15,817)
Stock options exercised	565	533	885
Net cash used in financing activities	282,980	244,649	111,595
Net (decrease) increase in cash and cash equivalents	780	(6,940)	(15,296)
Cash and cash equivalents, beginning of year	33,485	40,425	55,721
Cash and cash equivalents, end of year	34,265	33,485	40,425
Holding Company [Member]
Operating activities:
Net income	44,239	37,752	34,331
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of the Bank	(24,105)	(21,450)	(14,835)
Net gain on sale of securities		(17)
Deferred income tax (benefit) provision	17	(2,348)	858
Fair value adjustments for financial assets and financial liabilities	(779)	5,475	(1,991)
Stock based compensation expense	4,246	3,068	3,105
Net change in operating assets and liabilities	2,088	1,746	1,287
Net cash provided by operating activities	25,706	24,226	22,755
Investing activities:
Purchases of securities available for sale	(22)	(23)	(29)
Proceeds from sales and calls of securities available for sale	1,699	517
Net cash provided by (used in) investing activities	1,677	494	(29)
Financing activities:
Purchase of treasury stock	(18,872)	(14,151)	(5,622)
Cash dividends paid	(17,852)	(15,618)	(15,817)
Stock options exercised	565	533	956
Net cash used in financing activities	(36,159)	(29,236)	(20,483)
Net (decrease) increase in cash and cash equivalents	(8,776)	(4,516)	2,243
Cash and cash equivalents, beginning of year	16,525	21,041	18,798
Cash and cash equivalents, end of year	$ 7,749	$ 16,525	$ 21,041