Note 12 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Securities available-for-sale	$ 1,368,487	$ 1,314,345
Assets, fair value disclosure	1,372,623	1,316,664
Liabilities, fair value disclosure	6,366	6,997
Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	434,453	513,376
Assets, fair value disclosure	434,453	513,376
Liabilities, fair value disclosure
Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	934,034	800,969
Assets, fair value disclosure	938,073	803,209
Liabilities, fair value disclosure	6,366	6,997
Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Assets, fair value disclosure	97	79
Liabilities, fair value disclosure
US Treasury Securities [Member]
Securities available-for-sale	399,436	489,017
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	399,436	489,017
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
US Government Corporations and Agencies Securities [Member]
Securities available-for-sale	9,700
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	9,700
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale	393,722	390,331
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	393,722	390,331
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Commercial Mortgage Backed Securities [Member]
Securities available-for-sale	446,065	336,260
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	446,065	336,260
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale	1,931
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	1,931
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Collateralized Mortgage Obligations [Member]
Securities available-for-sale	1,710	28
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	1,710	28
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Corporate Debt Securities [Member]
Securities available-for-sale	80,906	74,350
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	80,906	74,350
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Mutual Funds [Member]
Securities available-for-sale	6,271	6,230
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	6,271	6,230
Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Preferred Stock of Government Sponsored Entities [Member]
Securities available-for-sale	8,087	7,308
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	8,087	7,308
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Other Equity Securities [Member]
Securities available-for-sale	20,659	10,821
Other Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	20,659	10,821
Other Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale
Other Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale
Warrant [Member]
Assets, fair value disclosure	97	79
Warrant [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure
Warrant [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure
Warrant [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	97	79
Interest Rate Swap [Member]
Assets, fair value disclosure	2,314	938
Liabilities, fair value disclosure	5,049	3,744
Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure
Liabilities, fair value disclosure
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	2,314	938
Liabilities, fair value disclosure	5,049	3,744
Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure
Liabilities, fair value disclosure
Foreign Exchange Contract [Member]
Assets, fair value disclosure	1,725	1,302
Liabilities, fair value disclosure	1,083	3,132
Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure
Liabilities, fair value disclosure
Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	1,725	1,302
Liabilities, fair value disclosure	1,083	3,132
Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure
Liabilities, fair value disclosure
Option Contracts [Member]
Liabilities, fair value disclosure	234	121
Option Contracts [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities, fair value disclosure
Option Contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities, fair value disclosure	234	121
Option Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities, fair value disclosure