Note 2 - Cash and Due From Banks (Details Textual) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Cash Reserve Deposit Required and Made	$ 64,076,000	$ 41,165,000

Cash deposited in a special reserve account for the exclusive benefit of customers pursuant to SEC Regulations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 305
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6478312&loc=d3e61473-112792

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant