Note 3 - Available-for-sale Securities - Carrying Amount of Securities and Fair Value (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Total, amortized cost	$ 39,890,615	$ 33,959,844
Available-for-sale securities, gross unrealized gains	820,459	118,187
Available-for-sale securities, gross unrealized losses	(138,692)	(649,373)
Available-for-sale securities, fair value	40,572,382	33,428,658
Asset-backed Securities [Member]
Total, amortized cost	30,677,663	28,799,904
Available-for-sale securities, gross unrealized gains	452,357	115,824
Available-for-sale securities, gross unrealized losses	(123,641)	(605,370)
Available-for-sale securities, fair value	31,006,379	28,310,358
US Government Agencies Debt Securities [Member]
Total, amortized cost	1,169,731	1,487,917
Available-for-sale securities, gross unrealized gains	3,923
Available-for-sale securities, gross unrealized losses	(15,051)	(42,885)
Available-for-sale securities, fair value	1,158,603	1,445,032
US States and Political Subdivisions Debt Securities [Member]
Total, amortized cost	8,043,221	3,672,023
Available-for-sale securities, gross unrealized gains	364,179	2,363
Available-for-sale securities, gross unrealized losses		(1,118)
Available-for-sale securities, fair value	$ 8,407,400	$ 3,673,268

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

No definition available.

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

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

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

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

+ Details

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

- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: