Note 7 - Fair Value Measurements - Carrying Value and Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands		Mar. 31, 2021	Dec. 31, 2020
Restricted equity securities		$ 5,089	$ 5,089
Reported Value Measurement [Member]
Cash and cash equivalents		456,529	338,856
Loans, net		2,294,999	2,282,766
Restricted equity securities		5,089	5,089
Accrued interest receivable		7,933	7,516
Deposits		3,140,826	2,960,595
Federal Home Loan Bank borrowings		0	3,638
Accrued interest payable		2,236	3,051
Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	[1]	456,529	338,856
Loans, net	[1]	2,296,988	2,302,530
Accrued interest receivable	[1]	7,933	7,516
Deposits	[1]	2,896,171	2,796,339
Federal Home Loan Bank borrowings	[1]	0	3,755
Accrued interest payable	[1]	2,236	3,051
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents		456,529	338,856
Loans, net		0	0
Accrued interest receivable		1	1
Deposits		0	0
Federal Home Loan Bank borrowings		0	0
Accrued interest payable		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Cash and cash equivalents		0	0
Loans, net		0	0
Accrued interest receivable		2,099	2,210
Deposits		0	0
Federal Home Loan Bank borrowings		0	0
Accrued interest payable		0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Cash and cash equivalents		0	0
Loans, net		2,296,988	2,302,530
Accrued interest receivable		5,833	5,305
Deposits		2,896,171	2,796,339
Federal Home Loan Bank borrowings		0	3,755
Accrued interest payable		$ 2,236	$ 3,051

[1] Estimated fair values are consistent with an exit-price concept. The assumptions used to estimate the fair values are intended to approximate those that a market-participant would realize in a hypothetical orderly transaction.