Note 4 - Loans and Allowance for Credit Losses (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Mar. 31, 2025	Dec. 31, 2024	Dec. 21, 2024	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Unamortized Loan Cost (Fee)	$ 300		$ 300			$ 1,100
Interest Receivable	20,884		20,884			20,075
Proceeds from Sale of Notes Receivable			12,331	$ 0
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss	4,044,657		4,044,657			3,992,534
Off-Balance-Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)	1,200	$ 275,000	2,700	500
Debt Securities, Held-to-Maturity, Credit Loss Expense (Reversal)	2	56	4	62
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest	59,278	38,332	59,278	38,332	$ 61,929	59,929		$ 36,584	$ 35,843
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Period Increase (Decrease)			$ 600
Percentage of Increase in Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest			1.10%
Loans and Leases Receivables, Impaired, Troubled Debt, Interest Income	1,100	200
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
Asset Pledged as Collateral [Member] | FHLB Borrowings, Deposits, and Other [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss	2,900,000		2,900,000			2,900,000
Loans Receivable [Member]
Interest Receivable	17,500		17,500			16,400
Non-mortgage Loans [Member]
Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance	50,160		50,160			$ 0
Financing Receivable, Transfer to Held-for-Sale, Valuation Allowance, Expense	78
Proceeds from Sale of Notes Receivable	12,300
Financing Receivable, Excluding Accrued Interest, Transfer out, Allowance for Credit Loss, Expense Reversal	78		78
Metro Phoenix Bank and HMN Financial Inc. [Member]
Financing Receivable, Unamortized Purchase Premium (Discount)	$ 52,700		$ 52,700				$ 70,600