Note 12 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017
Debt Securities, Available-for-sale, Total	$ 1,241,105,000	$ 1,333,626,000	$ 1,300,000,000
Equity Securities, FV-NI	24,154,000	28,100,000
Assets, fair value disclosure	1,278,667,000	1,340,767,000
Liabilities, fair value disclosure	927,000	3,161,000
Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	124,595,000	277,622,000
Equity Securities, FV-NI	24,154,000
Assets, fair value disclosure	148,749,000	277,622,000
Liabilities, fair value disclosure
Fair Value, Inputs, Level 2 [Member]
Debt Securities, Available-for-sale, Total	1,116,510,000	1,056,004,000
Equity Securities, FV-NI
Assets, fair value disclosure	1,129,723,000	1,063,054,000
Liabilities, fair value disclosure	927,000	3,161,000
Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Equity Securities, FV-NI
Assets, fair value disclosure	195,000	91,000
Liabilities, fair value disclosure
US Treasury Securities [Member]
Debt Securities, Available-for-sale, Total	124,595,000	249,520,000
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total	124,595,000	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	8,695,000	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	8,695,000	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	385,920,000	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	385,920,000	390,336,000
US Government-sponsored Enterprises Debt 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	904,000	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	904,000	1,914,000
US States and Political Subdivisions 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	638,359,000	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	638,359,000	571,969,000
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale, Total
Collateralized Mortgage Obligations [Member]
Debt Securities, Available-for-sale, Total	1,371,000	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	1,371,000	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	81,261,000	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	81,261,000	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	6,129,000
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total		6,230,000
Equity Securities, FV-NI	6,129,000
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	6,691,000
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	6,691,000
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	11,334,000
Other Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Debt Securities, Available-for-sale, Total		11,770,000
Equity Securities, FV-NI	11,334,000
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	195,000	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	195,000	91,000
Interest Rate Swap [Member]
Assets, fair value disclosure	11,674,000	5,218,000
Liabilities, fair value disclosure		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	11,674,000	5,218,000
Liabilities, fair value disclosure		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	1,539,000	1,832,000
Liabilities, fair value disclosure	924,000	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	1,539,000	1,832,000
Liabilities, fair value disclosure	924,000	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	3,000	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	3,000	9,000
Option Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities, fair value disclosure