Note 11 - Borrowing Arrangements (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	May 03, 2023	Dec. 31, 2022
Financing Receivable, before Allowance for Credit Loss	$ 3,120,952,000		$ 3,120,952,000			$ 3,336,449,000
Long-Term Federal Home Loan Bank Advances	$ 150,000,000		$ 150,000,000
Federal Home Loan Bank, Advances, Activity for Year, Average Interest Rate at Period End	1.18%		1.18%
Advances from Federal Home Loan Banks, Total	$ 150,000,000		$ 150,000,000			220,000,000
State of California [Member]
Interest-Bearing Domestic Deposit, Certificates of Deposits					$ 30,000,000
Federal Home Loan Bank Advances [Member]
Debt Instrument, Term (Year)			5 years
Interest Paid, Including Capitalized Interest, Operating and Investing Activities	440,000	$ 1,000,000	$ 2,400,000	$ 2,000,000
Federal Reserve Bank of San Francisco Secured Line of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity	41,900,000		41,900,000
Federal Reserve Bank of San Francisco Secured Line of Credit [Member] | Asset Pledged as Collateral [Member]
Financing Receivable, before Allowance for Credit Loss	63,300,000		63,300,000
Federal Home Loan Bank Secured Line of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity	1,100,000,000		1,100,000,000
Federal Home Loan Bank Secured Line of Credit [Member] | Asset Pledged as Collateral [Member]
Financing Receivable, before Allowance for Credit Loss	1,500,000,000		1,500,000,000
Federal Home Loan Bank Overnight Advances [Member]
Long-Term Federal Home Loan Bank Advances	0		0
Advances from Federal Home Loan Banks, Total	0		0			$ 0
Letters of Credit Outstanding, Amount					$ 30,000,000
Other Financial Institutions [Member]
Line of Credit Facility, Maximum Borrowing Capacity	92,000,000		92,000,000
Wells Fargo Bank [Member] | Line of Credit [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,000,000		$ 2,000,000