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Investment securities pledged as collateral.

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Note 10 - Borrowed Funds (Details Textual) - USD ($)					3 Months Ended
Note 10 - Borrowed Funds (Details Textual) - USD ($)	Nov. 14, 2017	Nov. 04, 2017	Oct. 12, 2017	Jul. 14, 2017	Mar. 31, 2018	Dec. 31, 2017
Securities Sold under Agreements to Repurchase, Total					$ 100,000,000	$ 100,000,000
Weighted Average Rate Of Securities Sold Under Agreements					2.86%
Advances from Federal Home Loan Banks, Total					$ 325,000,000	430,000,000
SinoPac Bancorp [Member]
Payments to Acquire Businesses, Gross	$ 100,000,000	$ 100,000,000		$ 284,984,000
Business Combination, Deferred Payments	$ 35,400,000				$ 35,200,000
Business Combination, Deferred Payments, Disbursed Rate, In Next Twelve Months					50.00%
Business Combination, Deferred Payments, Disbursed Rate, In Year Two					30.00%
Business Combination, Deferred Payments, Disbursed Rate, In Year Three					20.00%
Debt Instrument, Face Amount					$ 35,700,000	$ 35,200,000
Mature in April 2018 [Member]
Advances from Federal Home Loan Banks, Total					15,000,000
Mature in July 2018 [Member]
Advances from Federal Home Loan Banks, Total					5,000,000
Mature in October 2018 [Member]
Advances from Federal Home Loan Banks, Total					5,000,000
Mature in December 2019 [Member]
Advances from Federal Home Loan Banks, Total					$ 50,000,000
Business Combination, Deferred Payments [Member]
Debt Instrument, Interest Rate, Effective Percentage					2.80%
Business Combination, Deferred Payments [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate					1.50%
Term Loan [Member] \| US Bank [Member]
Debt Instrument, Interest Rate, Effective Percentage					3.438%	3.125%
Debt Instrument, Face Amount			$ 75,000,000
Debt Instrument, Periodic Payment, Principal			$ 4,700,000
Term Loan [Member] \| London Interbank Offered Rate (LIBOR) [Member] \| US Bank [Member]
Debt Instrument, Basis Spread on Variable Rate			1.75%
Over-night Borrowings [Member]
Advances from Federal Home Loan Banks, Total					$ 250,000,000	$ 325,000,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate					1.87%	1.41%
Non Overnight Borrowings [Member]
Advances from Federal Home Loan Banks, Total					$ 75,000,000	$ 105,000,000
Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate					1.53%	1.41%
Securities Sold under Agreements to Repurchase [Member]
Investment Securities Pledged As Collateral					$ 107,600,000	$ 108,400,000
Non Callable Fixed Rate Securities [Member]
Number Of Securities Sold Under Agreements To Repurchase					2
Fixed Rate Non-callable Securities Sold Under Agreements to Repurchase [Member]
Securities Sold under Agreements to Repurchase, Total						$ 100,000,000
Weighted Average Rate Of Securities Sold Under Agreements						2.86%
Fixed Rate Non-callable Securities Sold Under Agreements to Repurchase [Member] \| Mature in June 2018 [Member]
Securities Sold under Agreements to Repurchase, Total					$ 50,000,000
Fixed Rate Non-callable Securities Sold Under Agreements to Repurchase [Member] \| Mature in July 2018 [Member]
Securities Sold under Agreements to Repurchase, Total					$ 50,000,000