Note 1 - Description of Business and Significant Accounting Policies (Details Textual)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) shares	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) shares	Dec. 31, 2019 USD ($) $ / shares shares	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)
Number of Wholly-Owned Operating Subsidiaries	5		5
Common Stock, Par or Stated Value Per Share (in dollars per share) | $ / shares	$ 0.10		$ 0.10		$ 0.10
Common Stock, Shares Authorized (in shares) | shares	20,000,000		20,000,000		20,000,000
Common Stock, Shares, Issued, Total (in shares) | shares	7,741,229		7,741,229		7,734,004
Weighted Average Number of Shares Outstanding, Basic and Diluted (in shares) | shares	7,740,876	7,697,969	7,737,418	7,673,690
Equity Securities, FV-NI					$ 10,987,539
Equity Securities, FV-NI, Unrealized Gain (Loss), Total			$ (497,194)	$ 845,817	1,098,760
Stockholders' Equity Attributable to Parent, Ending Balance	$ 14,885,772	$ 15,719,498	$ 14,885,772	15,719,498	16,876,197	$ 12,463,102	$ 14,411,202		$ 12,632,666
Equity Securities, FV-NI, Gain (Loss), Total					$ 1,100,000
Common Stock, Shares, Outstanding, Ending Balance (in shares) | shares	7,741,229		7,741,229		7,734,004
AOCI Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance	$ 3,517,249	1,502,174	$ 3,517,249	1,502,174	$ 2,329,495	624,464	160,109		(2,184,429)
Retained Earnings [Member]
Stockholders' Equity Attributable to Parent, Ending Balance	$ (12,566,699)	$ (9,695,078)	$ (12,566,699)	$ (9,695,078)	$ (9,436,956)	$ (12,140,327)	$ (9,660,296)		(8,937,404)
Cumulative Effect, Period of Adoption, Adjustment [Member]
Stockholders' Equity Attributable to Parent, Ending Balance
Cumulative Effect, Period of Adoption, Adjustment [Member] | AOCI Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance									1,098,760
Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings [Member]
Stockholders' Equity Attributable to Parent, Ending Balance									$ (1,098,760)
Accounting Standards Update 2016-01 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | AOCI Attributable to Parent [Member]
Stockholders' Equity Attributable to Parent, Ending Balance								$ 1,098,760
Accounting Standards Update 2016-01 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Retained Earnings [Member]
Stockholders' Equity Attributable to Parent, Ending Balance								$ (1,098,760)