Note 4 - Loans and Allowance for Credit Losses - Purchases of Loans Receivable (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Purchased Auto Loans [Member]
Purchases of loans receivable	$ 14,141,053	$ 10,356,577

The increase (decrease) during the reporting period in outstanding loans including accrued interest.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Name:	us-gaap_IncreaseDecreaseInFinanceReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration