Note 3 - U.S. Treasury Securities, Available-for-sale - Available-for-sale Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
U.S. Treasury securities, available for sale, amortized cost	$ 208,279	$ 134,715
Pledged assets, available for sale	207,861	135,133
U.S. Treasury Note, 4.125%, 10/31/2026 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost	20,008
Gross unrealized gains	0
Gross unrealized losses	(10)
Pledged assets, available for sale	19,998
U.S. Treasury Note, 0.5%, 4/30/2027 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost	98,015
Gross unrealized gains	0
Gross unrealized losses	(204)
Pledged assets, available for sale	97,811
U.S. Treasury Note, 4.5%, 5/15/2027 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost	65,726
Gross unrealized gains	0
Gross unrealized losses	(188)
Pledged assets, available for sale	65,538
U.S. Treasury Note, 2.25%, 8/15/2027 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost	24,530
Gross unrealized gains	0
Gross unrealized losses	(16)
Pledged assets, available for sale	24,514
US Treasury Securities [Member]
U.S. Treasury securities, available for sale, amortized cost	208,279	134,715
Gross unrealized gains	0	418
Gross unrealized losses	(418)	0
Pledged assets, available for sale	$ 207,861	135,133
U.S. Treasury Note, 0.75%, 5/31/2026 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost		34,579
Gross unrealized gains		23
Gross unrealized losses
Pledged assets, available for sale		34,602
U.S. Treasury Note, 4.625%, 6/30/2026 Maturity [Member]
U.S. Treasury securities, available for sale, amortized cost		100,136
Gross unrealized gains		395
Gross unrealized losses		0
Pledged assets, available for sale		$ 100,531

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).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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Amount, before tax, of unrealized loss 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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

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Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477657/942-210-S45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478478/942-210-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

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