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			9 Months Ended
		Sep. 30, 2021		Sep. 30, 2020	Sep. 30, 2021		Sep. 30, 2020	Dec. 31, 2020
Assets, fair value disclosure		$ 1,105,861			$ 1,105,861			$ 1,068,382
Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		27,418			27,418			41,920
Total Losses		(47)		$ 6,953	2,172		$ 7,774
Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		20,914			20,914			35,398
Total Losses		0		6,950	2,037		6,950
Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure		5,497	[1]		5,497	[1]		5,141	[2]
Total Losses	[1]	(55)		0	(8)		717
Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		1,007			1,007			1,381
Total Losses		8		3	143		107
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure		60,328			60,328			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		0	[1]		0	[1]		0	[2]
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		1,045,511			1,045,511			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		0	[1]		0	[1]		0	[2]
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		27,468			27,468			41,920
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		20,964			20,964			35,398
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure		5,497	[1]		5,497	[1]		5,141	[2]
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		1,007			1,007			1,381
Commercial Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		5,355			5,355			5,342
Total Losses		0		6,950	2,037		6,950
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		5,355			5,355			5,342
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		13,332			13,332			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		13,332			13,332			25,749
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		2,227			2,227			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		$ 2,277			$ 2,277			$ 4,307

[1] Other real estate owned balance of $5.3 million in the Consolidated Balance Sheets is net of estimated disposal costs.

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