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Note 4 - Loans and Allowance for Credit Losses (Details Textual) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Jun. 30, 2025	Dec. 31, 2024	Dec. 21, 2024	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Unamortized Loan Cost (Fee)	$ 400		$ 400			$ 1,100
Interest Receivable	21,602		21,602			20,075
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss	4,102,075		4,102,075			3,992,534
Off-Balance-Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	1,100	$ 549	3,900	$ 31
Debt Securities, Held-to-Maturity, Credit Loss Expense (Reversal)	2	14	6	76
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	62,127	39,142	62,127	39,142	$ 59,278	59,929		$ 38,332	$ 35,843
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Period Increase (Decrease)			$ 2,200
Percentage of Increase in Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest			3.70%
Loans and Leases Receivables, Impaired, Troubled Debt, Interest Income	1,500	1,900
Financing Receivable, Nonaccrual, Interest Income	0	0
Financing Receivable, Excluding Accrued Interest, Modified in Period, Amount	0	0		0
Financing Receivable, Excluding Accrued Interest, Modified, Subsequent Default	0	$ 0	$ 0	$ 0
Asset Pledged as Collateral [Member] | FHLB Borrowings, Deposits, and Other [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss	2,600,000		2,600,000			2,900,000
Loans Receivable [Member]
Interest Receivable	18,300		18,300			$ 16,400
Non-mortgage Loans [Member]
Financing Receivable, Excluding Accrued Interest, Transfer out, Allowance for Credit Loss, Expense Reversal			78
Metro Phoenix Bank and HMN Financial Inc. [Member]
Financing Receivable, Unamortized Purchase Premium (Discount)	$ 47,300		$ 47,300				$ 70,600

X

- Definition

The gross interest income that would have been recorded in the period on troubled debt restructurings, if the loans had been current in accordance with their original terms and had been outstanding throughout the period or since origination, if held for part of the period.

+ References

No definition available.

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- Definition

The percentage of increase in amount, excluding accrued interest, of allowance for credit loss on financing receivable.

+ References

No definition available.

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- Definition

Amount of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
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+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Amortized cost excluding accrued interest, of financing receivable modified during period for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
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Amortized cost excluding accrued interest, of financing receivable with payment default in current period and modified within previous 12 months preceding payment default for debtor experiencing financial difficulty.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
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- Definition

Amount, excluding accrued interest, of reversal of credit loss expense on financing receivable transferred out of held-for-investment into held-for-sale classification. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Amount of interest income on financing receivable on nonaccrual status.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
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- Definition

Amount of unamortized loan commitment, origination, and other costs (fees) on financing receivable recognized as adjustment to yield. Excludes financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Amount of unamortized purchase premium (discount) on financing receivable. Excludes financing receivable covered under loss sharing agreement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 310
-SubTopic 20
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-URI https://asc.fasb.org/1943274/2147481598/310-20-45-1

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- Definition

Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
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-Paragraph 1
-Subparagraph (SX 210.5-02(3)(a)(4))
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- Definition

Amount of expense (reversal of expense) for expected credit loss for off-balance sheet credit exposure. Excludes off-balance sheet credit exposure accounted for as insurance and instrument accounted for under derivatives and hedging.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
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