Note 4 - Acquisition - Fair Value of Assets and Liabilities Acquired (Details) - USD ($)				3 Months Ended
	Nov. 14, 2017	Nov. 04, 2017	Jul. 14, 2017	Mar. 31, 2018	Mar. 31, 2017
Liabilities assumed:
Gain from acquisition				$ 340,000
SinoPac Bancorp [Member]
Assets acquired:
Cash and cash equivalents			$ 166,932,000
Short-term investments			122,000,000
Securities available-for-sale			88,044,000
FHLB and FRB stock			19,890,000
Loans			705,792,000
Premises and equipment			6,239,000
Cash surrender value of life insurance			46,083,000
Deferred tax assets, net			40,690,000
Core deposit intangible			6,122,000
Accrued interest receivable and other assets			10,689,000
Total assets acquired			1,212,481,000
Liabilities assumed:
Deposits			813,888,000
Advances from the Federal Home Loan Bank			30,000,000
Accrued interest payable and other liabilities			8,512,000
Total liabilities assumed			852,400,000
Net assets acquired			360,081,000
Cash paid	$ 100,000,000	$ 100,000,000	284,984,000
Fair value of common stock issued			34,862,000
Total consideration paid			319,846,000
Purchase price payable to SinoPac			34,267,000
Total consideration			354,113,000
Gain from acquisition			$ 5,968,000