Note 13 - Fair Value Measurements - Financial Assets and Liabilities Measured on a Non-recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2020		Sep. 30, 2019		Sep. 30, 2020		Sep. 30, 2019		Dec. 31, 2019		Dec. 31, 2018
Assets, fair value disclosure	$ 1,110,752				$ 1,110,752				$ 1,484,478
Total Losses	6,953		$ 203		7,774		$ 715		848		$ (289)
Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	55,833				55,833				49,519
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	122,944				122,944				102,941
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	987,788				987,788				1,381,498
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	905				905				6,490
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	20				20				39
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	54,928				54,928				43,029
Impaired Loans [Member]
Total Losses	6,950		0		6,950		0		0		0
Impaired Loans [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	49,309				49,309				37,082
Impaired Loans [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	49,309				49,309				37,082
Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Total Losses	6,950		0		6,950		0		0		0
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	13,167				13,167				6,196
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	13,167				13,167				6,196
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Total Losses	0		0		0		0		0		0
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	30,437				30,437				25,566
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	30,437				30,437				25,566
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Total Losses	0		0		0		0		0		0
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,705				5,705				5,320
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,705				5,705				5,320
Loans Held-for-sale [Member]
Total Losses	0		120		0		120
Loans Held-for-sale [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Loans Held-for-sale [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Loans Held-for-sale [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Loans Held-for-sale [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Other Real Estate Owned [Member]
Total Losses	0	[1],[2]	0	[1],[2]	717	[1],[2]	494	[1],[2]	681	[3]	(619)	[3]
Other Real Estate Owned [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,143	[1]			5,143	[1]			10,833	[3]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0	[1]			0	[1]			0	[3]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	905	[1]			905	[1]			6,490	[3]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	4,238	[1]			4,238	[1]			4,343	[3]
Investments in Venture Capital [Member]
Total Losses	3		$ 83		107		$ 101		167		$ 330
Investments in Venture Capital [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	1,381				1,381				1,604
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0				0
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	$ 1,381				$ 1,381				$ 1,604

[1] Other real estate owned balance of $4.9 million in the condensed consolidated balance sheet is net of estimated disposal costs.

[2] Other real estate owned balance of $9.0 million in the condensed consolidated balance sheet is net of estimated disposal costs.

[3] Other real estate owned balance of $10.2 million in the Consolidated Balance Sheets is net of estimated disposal costs.