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		12 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Assets, fair value disclosure		$ 936,359		$ 1,068,382
Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		31,522		41,920
Total Losses		71	$ 369	7,836	$ 848
Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		25,287		35,398
Total Losses		0	0	7,012	0
Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	5,141		5,141
Total Losses	[1]	0	336	717	681
Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		1,094		1,381
Total Losses		71	33	107	167
Fair Value, Inputs, Level 1 [Member]
Assets, fair value disclosure		61,713		104,692
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0
Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	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
Fair Value, Inputs, Level 2 [Member]
Assets, fair value disclosure		874,630		963,669
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		905		905
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		0		0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	905		905
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
Fair Value, Inputs, Level 3 [Member]
Assets, fair value disclosure		16		21
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member]
Assets, fair value disclosure		30,617		41,015
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		25,287		35,398
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Other Real Estate Owned [Member]
Assets, fair value disclosure	[1]	4,236		4,236
Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Investments in Venture Capital and Private Company Stock [Member]
Assets, fair value disclosure		1,094		1,381
Commercial Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		14,258		5,342
Total Losses		0	0	7,012	0
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		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
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		14,258		5,342
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		11,029		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
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
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure		$ 11,029		25,749
Residential Mortgage and Equity Lines Portfolio Segment [Member] | Fair Value, Nonrecurring [Member] | Loans Receivable [Member]
Assets, fair value disclosure				4,307
Total Losses				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
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
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				$ 4,307

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