Note 15 - Fair Value Measurements - Changes in Level 3 Assets (Details) - Fair Value, Inputs, Level 3 [Member] - Fair Value, Recurring [Member] $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Balance at Beginning of Period	$ 0
Transfers Into Level 3	1,540	[1]
Purchases	7,372
Unrealized	0
Total	8,912
Corporate Debt Securities [Member]
Balance at Beginning of Period	0
Transfers Into Level 3	1,540	[1]
Purchases	1,000
Unrealized	0
Total	2,540
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Balance at Beginning of Period	0
Transfers Into Level 3	0	[1]
Purchases	6,372
Unrealized	0
Total	$ 6,372

[1] Transferred from Level 2 to Level 3 because of a lack of observable market data, resulting from little to no market activity for the securities.