Note 3 - U.S. Treasury Securities, Available-for-sale - Available-for-sale- Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
U.S. Treasury securities, available for sale, amortized cost	$ 125,154	$ 100,412
Pledged assets, available for sale	125,543	100,551
U.S. Treasury Note, 4.625%, 6/30/2026 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost	100,343	100,412
Gross unrealized gains	389	139
Gross unrealized losses	0	0
Pledged assets, available for sale	100,732	100,551
U.S. Treasury Bill maturing 6/5/2025 [Member]
U.S. Treasury securities, available for sale, amortized cost	24,811
Gross unrealized gains	0
Gross unrealized losses	0
Pledged assets, available for sale	24,811
US Treasury Securities [Member]
U.S. Treasury securities, available for sale, amortized cost	125,154	100,412
Gross unrealized gains	389	139
Gross unrealized losses	0	0
Pledged assets, available for sale	$ 125,543	$ 100,551