Note 12 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale, Total	$ 1,475,949,000	$ 1,333,626,000
Equity Securities, FV-NI	23,131,000	28,100,000
Assets, fair value disclosure	1,514,446,000	1,340,767,000
Liabilities, fair value disclosure	2,249,000	3,161,000
Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	348,544,000	277,622,000
Equity Securities, FV-NI	23,131,000
Assets, fair value disclosure	371,675,000	277,622,000
Liabilities, fair value disclosure
Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	1,127,405,000	1,056,004,000
Equity Securities, FV-NI
Assets, fair value disclosure	1,142,595,000	1,063,054,000
Liabilities, fair value disclosure	2,249,000	3,161,000
Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Equity Securities, FV-NI
Assets, fair value disclosure	176,000	91,000
Liabilities, fair value disclosure
US Treasury Securities [Member]
Debt Securities, Available-for-sale, Total	348,544,000	249,520,000
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	348,544,000	249,520,000
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
US Government Corporations and Agencies Securities [Member]
Debt Securities, Available-for-sale, Total	8,189,000	8,988,000
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	8,189,000	8,988,000
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
US Government-sponsored Enterprises Debt Securities [Member]
Debt Securities, Available-for-sale, Total	383,959,000	390,336,000
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	383,959,000	390,336,000
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale, Total	658,288,000	571,969,000
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	658,288,000	571,969,000
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
US States and Political Subdivisions Debt Securities [Member]
Debt Securities, Available-for-sale, Total		1,914,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total		1,914,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale, Total	1,203,000	1,516,000
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	1,203,000	1,516,000
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Corporate Debt Securities [Member]
Debt Securities, Available-for-sale, Total	75,766,000	81,281,000
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	75,766,000	81,281,000
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Mutual Funds [Member]
Debt Securities, Available-for-sale, Total		6,230,000
Equity Securities, FV-NI	6,082,000
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total		6,230,000
Equity Securities, FV-NI	6,082,000
Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total
Equity Securities, FV-NI
Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Equity Securities, FV-NI
Preferred Stock of Government Sponsored Entities [Member]
Debt Securities, Available-for-sale, Total		10,102,000
Equity Securities, FV-NI	7,480,000
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total		10,102,000
Equity Securities, FV-NI	7,480,000
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total
Equity Securities, FV-NI
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Equity Securities, FV-NI
Other Equity Securities [Member]
Debt Securities, Available-for-sale, Total		11,770,000
Equity Securities, FV-NI	9,569,000
Other Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total		11,770,000
Equity Securities, FV-NI	9,569,000
Other Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total
Equity Securities, FV-NI
Other Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Equity Securities, FV-NI
Warrant [Member]
Assets, fair value disclosure	176,000	91,000
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	176,000	91,000
Interest Rate Swap [Member]
Assets, fair value disclosure	14,801,000	5,218,000
Liabilities, fair value disclosure	157,000	2,699,000
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	14,801,000	5,218,000
Liabilities, fair value disclosure	157,000	2,699,000
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	389,000	1,832,000
Liabilities, fair value disclosure	2,083,000	453,000
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	389,000	1,832,000
Liabilities, fair value disclosure	2,083,000	453,000
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	9,000	9,000
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	9,000	9,000
Option Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities, fair value disclosure