Note 3 - Debt and Equity Securities - Gross Unrealized Losses and Fair Value of Company's Investments (Details) $ in Thousands	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Available-for-Sale Securities, Less than 12 Months, Fair Value	$ 65,284	$ 110,599
Available-for-Sale Securities, Less than 12 Months, Unrealized Losses	$ 1,603	$ 1,240
Available-for-Sale Securities, Less than 12 Months, Number of Securities Included	52	62
Available-for-Sale Securities, 12 Months or More, Fair Value	$ 6,336	$ 92,750
Available-for-Sale Securities, 12 Months or More, Unrealized Losses	$ 94	$ 730
Available-for-Sale Securities, 12 Months or More, Number of Securities Included	17	75
Available-for-Sale Securities, Total, Fair Value	$ 71,620	$ 203,349
Available-for-Sale Securities, Total, Unrealized Losses	1,697	1,970
US Government-sponsored Enterprises Debt Securities [Member]
Available-for-Sale Securities, Less than 12 Months, Fair Value	7,093	16,507
Available-for-Sale Securities, Less than 12 Months, Unrealized Losses	$ 121	$ 114
Available-for-Sale Securities, Less than 12 Months, Number of Securities Included	3	5
Available-for-Sale Securities, 12 Months or More, Fair Value	$ 0	$ 24,658
Available-for-Sale Securities, 12 Months or More, Unrealized Losses	$ 0	$ 90
Available-for-Sale Securities, 12 Months or More, Number of Securities Included	0	9
Available-for-Sale Securities, Total, Fair Value	$ 7,093	$ 41,165
Available-for-Sale Securities, Total, Unrealized Losses	121	204
Collateralized Mortgage Backed Securities [Member]
Available-for-Sale Securities, Less than 12 Months, Fair Value	17,935	45,862
Available-for-Sale Securities, Less than 12 Months, Unrealized Losses	$ 206	$ 182
Available-for-Sale Securities, Less than 12 Months, Number of Securities Included	9	21
Available-for-Sale Securities, 12 Months or More, Fair Value	$ 5,163	$ 56,917
Available-for-Sale Securities, 12 Months or More, Unrealized Losses	$ 52	$ 453
Available-for-Sale Securities, 12 Months or More, Number of Securities Included	14	52
Available-for-Sale Securities, Total, Fair Value	$ 23,098	$ 102,779
Available-for-Sale Securities, Total, Unrealized Losses	258	635
Asset-backed Securities [Member]
Available-for-Sale Securities, Less than 12 Months, Fair Value	9,664	17,807
Available-for-Sale Securities, Less than 12 Months, Unrealized Losses	$ 403	$ 161
Available-for-Sale Securities, Less than 12 Months, Number of Securities Included	2	10
Available-for-Sale Securities, 12 Months or More, Fair Value	$ 0	$ 7,317
Available-for-Sale Securities, 12 Months or More, Unrealized Losses	$ 0	$ 142
Available-for-Sale Securities, 12 Months or More, Number of Securities Included	0	4
Available-for-Sale Securities, Total, Fair Value	$ 9,664	$ 25,124
Available-for-Sale Securities, Total, Unrealized Losses	403	303
US States and Political Subdivisions Debt Securities [Member]
Available-for-Sale Securities, Less than 12 Months, Fair Value	30,592	30,423
Available-for-Sale Securities, Less than 12 Months, Unrealized Losses	$ 873	$ 783
Available-for-Sale Securities, Less than 12 Months, Number of Securities Included	38	26
Available-for-Sale Securities, 12 Months or More, Fair Value	$ 1,173	$ 3,858
Available-for-Sale Securities, 12 Months or More, Unrealized Losses	$ 42	$ 45
Available-for-Sale Securities, 12 Months or More, Number of Securities Included	3	10
Available-for-Sale Securities, Total, Fair Value	$ 31,765	$ 34,281
Available-for-Sale Securities, Total, Unrealized Losses	$ 915	$ 828

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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