Note 3 - U.S. Treasury Securities, Available-for-sale - Available-for-sale- Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
U.S. Treasury securities, available for sale, amortized cost	$ 98,092	$ 148,803
Pledged assets, available for sale	98,099	148,820
Treasury Bill 10/24/2024 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost	49,176
Gross unrealized gains	0
Gross unrealized losses	(4)
Pledged assets, available for sale	49,172
Gross unrealized losses	4
Treasury Bill 11/29/2024 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost	48,916
Gross unrealized gains	11
Gross unrealized losses	0
Pledged assets, available for sale	48,927
Gross unrealized losses	0
US Treasury Securities [Member]
U.S. Treasury securities, available for sale, amortized cost	98,092	148,803
Gross unrealized gains	11	17
Gross unrealized losses	(4)	0
Pledged assets, available for sale	98,099	148,820
Gross unrealized losses	$ 4	0
Treasury Bill 1/2/2024 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost		49,671
Gross unrealized gains		9
Gross unrealized losses		0
Pledged assets, available for sale		49,680
Gross unrealized losses		0
Treasury Bill 2/15/2024 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost		49,992
Gross unrealized gains		8
Gross unrealized losses		0
Pledged assets, available for sale		50,000
Gross unrealized losses		0
Treasury Bill 4/30/2024 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost		49,140
Gross unrealized gains		0
Gross unrealized losses		0
Pledged assets, available for sale		49,140
Gross unrealized losses		$ 0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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