Note 13 - Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Securities available-for-sale	$ 1,471,584	$ 1,242,509
Equity securities	32,498	25,098
Assets, fair value disclosure	1,506,204	1,275,998
Liabilities, fair value disclosure	14,669	3,312
Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	49,791	124,751
Equity securities	32,498	25,098
Assets, fair value disclosure	82,289	149,849
Liabilities, fair value disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	1,421,793	1,117,758
Equity securities	0	0
Assets, fair value disclosure	1,423,871	1,125,965
Liabilities, fair value disclosure	14,669	3,312
Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Equity securities	0	0
Assets, fair value disclosure	44	184
Liabilities, fair value disclosure	0	0
US Treasury Securities [Member]
Securities available-for-sale	49,791	124,751
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	49,791	124,751
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	0	0
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
US Government Corporations and Agencies Securities [Member]
Securities available-for-sale	77,252
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	77,252
US Government Corporations and Agencies Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0
US Government Agencies Debt Securities [Member]
Securities available-for-sale		5,871
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale		0
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale		5,871
US Government Agencies Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale		0
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale	398,340	388,363
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	398,340	388,363
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Commercial Mortgage Backed Securities [Member]
Securities available-for-sale	846,105	656,744
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	846,105	656,744
Commercial Mortgage Backed Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Collateralized Mortgage Obligations [Member]
Securities available-for-sale	777	977
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	777	977
Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Corporate Debt Securities [Member]
Securities available-for-sale	99,319	65,803
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	0	0
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	99,319	65,803
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	0	0
Mutual Funds [Member]
Equity securities	6,259	6,094
Mutual Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Equity securities	6,259	6,094
Mutual Funds [Member] | Fair Value, Inputs, Level 2 [Member]
Equity securities	0	0
Mutual Funds [Member] | Fair Value, Inputs, Level 3 [Member]
Equity securities	0	0
Preferred Stock of Government Sponsored Entities [Member]
Equity securities	14,183	7,822
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 1 [Member]
Equity securities	14,183	7,822
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 2 [Member]
Equity securities	0	0
Preferred Stock of Government Sponsored Entities [Member] | Fair Value, Inputs, Level 3 [Member]
Equity securities	0	0
Other Equity Securities [Member]
Equity securities	12,056	11,182
Other Equity Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Equity securities	12,056	11,182
Other Equity Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Equity securities	0	0
Other Equity Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Equity securities	0	0
Warrant [Member]
Assets, fair value disclosure	44	184
Warrant [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	0	0
Warrant [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	0	0
Warrant [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	44	184
Interest Rate Swap [Member]
Assets, fair value disclosure	1,440	7,810
Liabilities, fair value disclosure	13,779	1,543
Interest Rate Swap [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	0	0
Liabilities, fair value disclosure	0	0
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	1,440	7,810
Liabilities, fair value disclosure	13,779	1,543
Interest Rate Swap [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	0	0
Liabilities, fair value disclosure	0	0
Foreign Exchange Contract [Member]
Assets, fair value disclosure	638	397
Liabilities, fair value disclosure	876	1,763
Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	0	0
Liabilities, fair value disclosure	0	0
Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	638	397
Liabilities, fair value disclosure	876	1,763
Foreign Exchange Contract [Member] | Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	0	0
Liabilities, fair value disclosure	0	0
Option Contracts [Member]
Liabilities, fair value disclosure	14	6
Option Contracts [Member] | Fair Value, Inputs, Level 1 [Member]
Liabilities, fair value disclosure	0	0
Option Contracts [Member] | Fair Value, Inputs, Level 2 [Member]
Liabilities, fair value disclosure	14	6
Option Contracts [Member] | Fair Value, Inputs, Level 3 [Member]
Liabilities, fair value disclosure	$ 0	$ 0