Note 13 - Fair Value Measurements and Fair Value of Financial Instruments - Financial Assets and Liabilities Measured on a Non-recurring Basis (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Assets, fair value disclosure		$ 1,031,221		$ 1,031,221		$ 1,068,382
Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		23,418		23,418		41,920
Total Losses		111	$ 452	182	$ 821
Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		17,312		17,312		35,398
Total Losses		0	0	0	0
Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	5,091		5,091		5,141
Total Losses	[1]	47	381	47	717
Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		1,015		1,015		1,381
Total Losses		64	71	135	104
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure		60,580		60,580		104,692
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		0		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	0		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		0		0		0
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure		970,619		970,619		963,669
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		0		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	0		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		0		0		0
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure		22		22		21
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		23,418		23,418		41,920
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		17,312		17,312		35,398
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	5,091		5,091		5,141
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		1,015		1,015		1,381
Commercial Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		2,059		2,059		5,342
Total Losses		0	0	0	0
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		2,059		2,059		5,342
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		11,742		11,742		25,749
Total Losses		0	0	0	0
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		11,742		11,742		25,749
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		3,511		3,511		4,307
Total Losses		0	$ 0	0	$ 0
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0		0
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		$ 3,511		$ 3,511		$ 4,307

[1] Other real estate owned balance of $4.9 million in the Consolidated Balance Sheets is net of estimated disposal costs.