Note 12 - Fair Value Measurements - Financial Assets and Liabilities Measured on a Non-recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2018		Jun. 30, 2017		Jun. 30, 2018		Jun. 30, 2017		Dec. 31, 2017		Dec. 31, 2016
Assets, fair value disclosure	$ 1,514,446				$ 1,514,446				$ 1,340,767
Total Losses	58		$ 875		264		$ 2,124		874		$ 1,307
Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	45,858				45,858				73,493
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	371,675				371,675				277,622
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	1,142,595				1,142,595				1,063,054
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	4,363				4,363				5,677
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	176				176				91
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	41,495				41,495				67,816
Impaired Loans [Member]
Total Losses			497				1,523		25		322
Impaired Loans [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	34,769				34,769				60,911
Impaired Loans [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	34,769				34,769				60,911
Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Total Losses			497				1,273		25		322
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	755				755				18,097
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	755				755				18,097
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Total Losses							250
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	26,409				26,409				31,459
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	26,409				26,409				31,459
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Total Losses
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	7,605				7,605				11,355
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	7,605				7,605				11,355
Other Real Estate Owned [Member]
Total Losses	(33)	[1]	212	[1]		[1]	249	[1]	457	[2]	9	[2]
Other Real Estate Owned [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	8,706	[1]			8,706	[1]			9,999	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure		[1]				[1]				[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	4,363	[1]			4,363	[1]			5,677	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	4,343	[1]			4,343	[1]			4,322	[2]
Equity Investments [Member]
Total Losses	91		$ 166		264		$ 352		392		$ 976
Equity Investments [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	2,383				2,383				2,583
Equity Investments [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Equity Investments [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure
Equity Investments [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Assets, fair value disclosure	$ 2,383				$ 2,383				$ 2,583

[1] Other real estate owned balance of $8.2 million in the condensed consolidated balance sheet is net of estimated disposal costs.

[2] Other real estate owned balance of $9.4 million in the Consolidated Balance Sheets is net of estimated disposal costs.