Note 5 - Loans - Loans Acquired in King Acquisition (Details) - USD ($) $ in Thousands		12 Months Ended
	May 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Non-accretable amount	$ 0	$ 0	$ 0	$ 0
Transfers between non-accretable and accretable	0	$ 0	$ 0	$ 0
Acquisition-day Fair Value	0
King Bancorp Inc. [Member]
Contractual receivable	165,744
Non-accretable amount	(1,579)
Accretable amount	(136)
Acquisition-day Fair Value	164,029
Contractual receivable	165,744
Transfers between non-accretable and accretable	(1,579)
Accretable amount	(136)
Acquisition-day Fair Value	164,029
King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	164,165
Non-accretable amount	0
Accretable amount	(136)
Acquisition-day Fair Value	164,029
Contractual receivable	164,165
Transfers between non-accretable and accretable	0
Accretable amount	(136)
Acquisition-day Fair Value	164,029
King Bancorp Inc. [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	1,579
Non-accretable amount	(1,579)
Accretable amount	0
Contractual receivable	1,579
Transfers between non-accretable and accretable	(1,579)
Accretable amount	0
Acquisition-day Fair Value	0
Commercial and Industrial Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	8,249
Non-accretable amount	0
Accretable amount	(23)
Acquisition-day Fair Value	8,226
Contractual receivable	8,249
Transfers between non-accretable and accretable	0
Accretable amount	(23)
Acquisition-day Fair Value	8,226
Construction and Development [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	18,738
Non-accretable amount	0
Accretable amount	86
Acquisition-day Fair Value	18,824
Contractual receivable	18,738
Transfers between non-accretable and accretable	0
Accretable amount	86
Acquisition-day Fair Value	18,824
Construction and Development [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	0
Accretable amount	0
Contractual receivable	0
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	135,650
Non-accretable amount	0
Accretable amount	(126)
Acquisition-day Fair Value	135,524
Contractual receivable	135,650
Transfers between non-accretable and accretable	0
Accretable amount	(126)
Acquisition-day Fair Value	135,524
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member] | Commercial Real Estate [Member]
Contractual receivable	84,219
Non-accretable amount	0
Accretable amount	(456)
Acquisition-day Fair Value	83,763
Contractual receivable	84,219
Transfers between non-accretable and accretable	0
Accretable amount	(456)
Acquisition-day Fair Value	83,763
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member] | Residential Loans [Member]
Contractual receivable	50,556
Non-accretable amount	0
Accretable amount	322
Acquisition-day Fair Value	50,878
Contractual receivable	50,556
Transfers between non-accretable and accretable	0
Accretable amount	322
Acquisition-day Fair Value	50,878
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member] | Home Equity Line of Credit [Member]
Contractual receivable	875
Non-accretable amount	0
Accretable amount	8
Acquisition-day Fair Value	883
Contractual receivable	875
Transfers between non-accretable and accretable	0
Accretable amount	8
Acquisition-day Fair Value	883
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	1,579
Non-accretable amount	(1,579)
Accretable amount	0
Contractual receivable	1,579
Transfers between non-accretable and accretable	(1,579)
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired with Credit Deterioration [Member] | Commercial Real Estate [Member]
Contractual receivable	1,351
Non-accretable amount	(1,351)
Accretable amount	0
Contractual receivable	1,351
Transfers between non-accretable and accretable	(1,351)
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired with Credit Deterioration [Member] | Residential Loans [Member]
Contractual receivable	228
Non-accretable amount	(228)
Accretable amount	0
Contractual receivable	228
Transfers between non-accretable and accretable	(228)
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired with Credit Deterioration [Member] | Home Equity Line of Credit [Member]
Contractual receivable	0
Non-accretable amount	0
Accretable amount	0
Contractual receivable	0
Transfers between non-accretable and accretable	0
Accretable amount	0
Acquisition-day Fair Value	0
Consumer Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	1,528
Non-accretable amount	0
Accretable amount	(73)
Acquisition-day Fair Value	1,455
Contractual receivable	1,528
Transfers between non-accretable and accretable	0
Accretable amount	(73)
Acquisition-day Fair Value	1,455
Consumer Portfolio Segment [Member] | King Bancorp Inc. [Member] | Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	0
Non-accretable amount	0
Accretable amount	0
Contractual receivable	0
Transfers between non-accretable and accretable	0
Accretable amount	0
Acquisition-day Fair Value	$ 0