Note 11 - Other Borrowings and Unused Lines of Credit - Unused Lines of Credit (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Unused lines of credit	$ 374,967,441	$ 381,409,192
Secured Debt [Member]
Unused lines of credit	2,967,441	34,409,192
Unsecured Debt [Member]
Unused lines of credit	$ 372,000,000	$ 347,000,000

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant