Note 4 - Fair Value Measurements - Assets Measured at Fair Value on Nonrecurring Basis (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2020	Dec. 31, 2019
Loans held for sale, Total gains (losses)		$ 64	$ (40)
Real estate, net(2), Total gains (losses)	[1]	0	0
Total, Total gains (losses)		93	(68)
Fair Value, Nonrecurring [Member]
Loans held for sale		4,884	3,606
Mortgage servicing rights, net		2,206	2,172
Mortgage servicing rights, net, Total gains (losses)		0	0
Impaired loans(1)	[2]	2,990	3,126
Impaired loans(1), Total gains (losses)	[2]	29	(28)
Real estate, net(2)	[1]	683	580
Total		10,763	9,484
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Loans held for sale		0	0
Mortgage servicing rights, net		0	0
Impaired loans(1)	[2]	0	0
Real estate, net(2)	[1]	0	0
Total		0	0
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Loans held for sale		4,884	3,606
Mortgage servicing rights, net		2,206	2,172
Impaired loans(1)	[2]	2,990	3,126
Real estate, net(2)	[1]	683	580
Total		10,763	9,484
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Loans held for sale		0	0
Mortgage servicing rights, net		0	0
Impaired loans(1)	[2]	0	0
Real estate, net(2)	[1]	0	0
Total		$ 0	$ 0

[1] Represents the fair value and related losses of foreclosed real estate and other collateral owned that were measured at fair value subsequent to their initial classification as foreclosed assets.

[2] Represents carrying value and related write-downs of loans for which adjustments are based on the appraised value of the collateral. The carrying value of loans fully charged-off is zero.