Note 5 - Stockholders' Equity (Details Textual) - USD ($)			12 Months Ended
	Nov. 18, 2016	Aug. 19, 2016	Dec. 31, 2017	Dec. 31, 2016	Jul. 31, 2012
Preferred Stock, Shares Outstanding			0
Stock Repurchased During Period, Value			$ 136,000	$ 15,000
Common Stock, Dividends, Per Share, Declared	$ 0.25	$ 1.25		$ 1.50
Dividends Payable				$ 36,000
Minimum [Member]
Equity Method Investment, Ownership Percentage				4.90%
Restricted Stock [Member]
Stock Repurchased During Period, Shares			163,214	6,862
Stock Repurchased During Period, Value			$ 135,000	$ 15,000
Preferred Stock [Member]
Excess Stock, Shares Authorized			1,000,000
Common Stock [Member]
Stock Repurchased During Period, Shares			(163,000)	(7,000)
Stock Repurchased During Period, Value
Common Stock [Member] | Privately Negotiated Transaction [Member]
Stock Repurchased During Period, Shares			0	400,000
Stock Repurchased During Period, Value				$ 1,000,000
Stock Repurchase Program, Authorized Amount					$ 5,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount			$ 3,000,000