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, 2020		Mar. 31, 2019		Dec. 31, 2019		Dec. 31, 2018
Assets, fair value disclosure	$ 1,378,354				$ 1,484,478
Total Losses	369		$ 74		848		$ (289)
Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	42,908				49,519
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure	18,790				102,941
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure	1,359,540				1,381,498
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,225				6,490
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure	24				39
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	37,683				43,029
Impaired Loans [Member]
Total Losses	0		0		0		0
Impaired Loans [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	31,926				37,082
Impaired Loans [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Impaired Loans [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Impaired Loans [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	31,926				37,082
Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Total Losses	0		0		0		0
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	6,325				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
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Impaired Loans [Member] | Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	6,325				6,196
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Total Losses	0		0		0		0
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	20,015				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
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
Impaired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	20,015				25,566
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member]
Total Losses	0		0		0		0
Impaired Loans [Member] | Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,586				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
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
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	5,586				5,320
Other Real Estate Owned [Member]
Total Losses	336	[1]	72	[1]	681	[2]	(619)	[2]
Other Real Estate Owned [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	9,463	[1]			10,833	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0	[1]			0	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	5,225	[1]			6,490	[2]
Other Real Estate Owned [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	4,238	[1]			4,343	[2]
Investments in Venture Capital [Member]
Total Losses	33		$ 2		167		$ 330
Investments in Venture Capital [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	1,519				1,604
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	0				0
Investments in Venture Capital [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure	$ 1,519				$ 1,604

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

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