Note 13 - Fair Value Measurements - Financial Assets and Liabilities Measured on a Non-recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Mar. 31, 2019		Mar. 31, 2018		Dec. 31, 2018		Dec. 31, 2017
Assets, fair value disclosure	$ 1,344,234				$ 1,275,998
Total Losses	74		$ 206		(289)		$ 874
Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	41,238				53,297
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	178,501				149,849
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	1,165,552				1,125,965
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	8,850				9,023
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	181				184
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	32,388				44,274
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Total Losses
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,973				6,850
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,973				6,850
Impaired Loans [Member]
Total Losses							25
Impaired Loans [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	25,984				37,769
Impaired Loans [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	25,984				37,769
Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Total Losses							25
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	440				4,733
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	440				4,733
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Total Losses
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	19,571				26,186
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	19,571				26,186
Other Real Estate Owned [Member]
Total Losses	72	[1]	33	[1]	(619)	[2]	457	[2]
Other Real Estate Owned [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	13,193	[1]			13,366	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		[1]				[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	8,850	[1]			9,023	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	4,343	[1]			4,343	[2]
Investments in Venture Capital [Member]
Total Losses	2		$ 173		330		$ 392
Investments in Venture Capital [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	2,061				2,162
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	$ 2,061				$ 2,162

[1] Other real estate owned balance of $12.5 million in the condensed consolidated balance sheet is net of estimated disposal costs.

[2] Other real estate owned balance of $12.7 million in the condensed consolidated balance sheet is net of estimated disposal costs.